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Review of Ancistrus (Siluriformes: Loricariidae) from the northwestern Guiana Shield, Orinoco Andes, and adjacent basins with description of six new species

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The Orinoco Andes and northwestern Guiana Shield (Essequibo, Orinoco, Branco, and upper Negro) were found to contain 11 species of Ancistrus, six of which are new. We additionally examine A. brevifilis from the Río Tuy of Venezuela and A. trinitatis from the island of Trinidad. The species in the region can be broken up into dorsoventrally flattened species (A. leoni new species, A. lithurgicus, and A. macropthalmus), white to yellow-dotted species (A. kellerae new species, A. nudiceps, and A. patronus new species), wide-jawed species (A. amaris new species and A. yutajae new species), and white-spotted species (A. brevifilis, A. leucostictus, A. trinitatis, A. saudades new species, and A. triradiatus). Distributions of Ancistrus support the Proto-Berbice hypothesis as A. saudades is found in the upper reaches of the Ventuari, Caura, and Caroni rivers, which were thought to have once flowed into the Proto-Berbice. In addition, although A. nudiceps does not appear to have split once the Takutu River was captured by the Branco, the progenitor of A. leucostictus and A. saudades did speciate with the populations on either side of the Rupununi Portal differing by 7% sequence divergence of the mitochondrial Cytochrome b gene. Besides the descriptions of the new species, we redescribe the others occurring in the area, and adjacent watersheds. We provide a key for their identification, and a preliminary hypothesis of relationships based on DNA sequences of the few species for which tissue samples are available.
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Accepted by F. Lima: 24 Dec. 2018; published: 7 Feb. 2019
ZOOTAXA
ISSN 1175-5326 (print edition)
ISSN
1175-5334
(online edition)
Copyright © 2019 Magnolia Press
Zootaxa 4552 (1): 001
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Monograph
https://doi.org/10.11646/zootaxa.4552.1.1
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ZOOTAXA
Review of Ancistrus (Siluriformes: Loricariidae) from the northwestern Guiana
Shield, Orinoco Andes, and adjacent basins with description of six new species
LESLEY S. DE SOUZA
1,4
, DONALD C. TAPHORN
2
& JONATHAN W. ARMBRUSTER
3
1
Field Museum of Natural History, 1400 S. Lake Shore, Chicago, IL 60605 USA
2
1822 N. Charles St., Belleville, IL, 62221 USA. E-mail: taphorn@gmail.com
3
Auburn University Museum of Natural History, 101 Rouse Life Sciences Building, Auburn University, AL 36849 USA.
E-mail: armbrjw@auburn.edu
4
Corresponding author. E-mail: ldesouza@fieldmuseum.org
Magnolia Press
Auckland, New Zealand
4552
DE SOUZA ET AL.
2
·
Zootaxa 4552 (1) © 2019 Magnolia Press
LESLEY S. DE SOUZA, DONALD C. TAPHORN & JONATHAN W. ARMBRUSTER
Review of Ancistrus (Siluriformes: Loricariidae) from the northwestern Guiana Shield, Orinoco Andes,
and adjacent basins with description of six new species
(Zootaxa 4552)
67 pp.; 30 cm.
7 Feb. 2019
ISBN 978-1-77670-592-4 (paperback)
ISBN 978-1-77670-593-1 (Online edition)
F
IRST
P
UBLISHED I
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2019 B
Y
Magnolia Press
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other than private research use.
ISSN 1175-5326 (Print edition)
ISSN 1175-5334 (Online edition)
Zootaxa 4552 (1) © 2019 Magnolia Press
·
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ANCISTRUS NORTHWESTERN GUIANA SHIELD ORINOCO ANDES
Table of contents
Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
Resumen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Resumo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Material and methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Key to the species of Ancistrus from the northwestern Guiana Shield, Orinoco Andes, and adjacent basins . . . . . . . . . . . . . . . . . . . . 8
Ancistrus amaris new species . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Ancistrus brevifilis Eigenmann 1920. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Ancistrus kellerae new species . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Ancistrus leoni, new species . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Ancistrus leucostictus (Günther 1864) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Ancistrus lithurgicus Eigenmann 1912 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Ancistrus macrophthalmus Pellegrin (1912) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Ancistrus nudiceps (Müller & Troschel 1849) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Ancistrus patronus, new species . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Ancistrus saudades new species . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Ancistrus trinitatis (Günther, 1864) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Ancistrus triradiatus Eigenmann 1918 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Ancistrus yutajae, new species . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
Literature cited. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Abstract
The Orinoco Andes and northwestern Guiana Shield (Essequibo, Orinoco, Branco, and upper Negro) were found to con-
tain 11 species of Ancistrus, six of which are new. We additionally examine A. brevifilis from the Río Tuy of Venezuela
and A. trinitatis from the island of Trinidad. The species in the region can be broken up into dorsoventrally flattened spe-
cies (A. leoni new species, A. lithurgicus, and A. macropthalmus), white to yellow-dotted species (A. kellerae new species,
A. nudiceps, and A. patronus new species), wide-jawed species (A. amaris new species and A. yutajae new species), and
white-spotted species (A. brevifilis, A. leucostictus, A. trinitatis, A. saudades new species, and A. triradiatus). Distribu-
tions of Ancistrus support the Proto-Berbice hypothesis as A. saudades is found in the upper reaches of the Ventuari, Cau-
ra, and Caroni rivers, which were thought to have once flowed into the Proto-Berbice. In addition, although A. nudiceps
does not appear to have split once the Takutu River was captured by the Branco, the progenitor of A. leucostictus and A.
saudades did speciate with the populations on either side of the Rupununi Portal differing by 7% sequence divergence of
the mitochondrial Cytochrome b gene. Besides the descriptions of the new species, we redescribe the others occurring in
the area, and adjacent watersheds. We provide a key for their identification, and a preliminary hypothesis of relationships
based on DNA sequences of the few species for which tissue samples are available.
Key words: Ancistrini, Colombia, Guyana, Venezuela, Taxonomy
Resumen
La Orinoquía y la parte noroeste del Escudo de Guyana (en las cuencas de los ríos Essequibo, Orinoco, Branco y el alto
río Negro) albergan 11 especies de Ancistrus, seis de las cuales son nuevas. También examinamos A. brevifilis del río Tuy
en Venezuela y A. trinitatis de la Isla de Trinidad. Las especies en la región se pueden dividir en especies deprimidas dor-
soventralmente (A. leoni n. sp., A. lithurgicus y A. macropthalmus), especies de puntos blancos o amarillos (A. kellerae
n. sp., A. nudiceps y A. patronus n. sp.), especies de mandíbula larga (A. amaris n. sp. y A. yutajae n. sp.) y especies de
manchas blancas (A. brevifilis, A. leucostictus, A. saudades n. sp. y A. triradiatus). Las observadas distribuciones de An-
cistrus apoyan la hipótesis del río Proto-Berbice, ya que A. saudades n. sp. se encuentra en las partes altas de los ríos Ven-
tuari, Caura y Caroní, que se cree que alguna vez fluyeron hacia el río Proto-Berbice. Además, aunque A. nudiceps no
parece haberse dividido una vez que el río Takutu fue capturado por el Branco, el progenitor de A. leucostictus y A. sau-
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dades sí se especiaba con las poblaciones a ambos lados del Portal Rupununi que difieren en un 7% en la secuencia del
gen mitocondrial del Citocromo b. Además de las descripciones de las nuevas especies, redescribimos las otras que ocur-
ren en el área y en las cuencas hidrográficas adyacentes. Proporcionamos una clave para su identificación y una hipótesis
preliminar de las relaciones basadas en las secuencias de ADN de las pocas especies para las cuales existen muestras de
tejido disponibles.
Resumo
Os Andes do Orinoco e o Escudo das Guianas do noroeste (Essequibo, Orinoco, Branco e Alto Negro) foram encontrados
para conter 11 espécies de Ancistrus, seis das quais são novas. Além disso, examinamos A. brevifilis do rio Tuy da Vene-
zuela e A. trinitatis da ilha de Trinidad. As espécies da região podem ser divididas em espécies achatadas dorsoventral-
mente (A. leoni n. sp., A. lithurgicus e A. macropthalmus), espécies com manchas brancas ou amarelas (A. kellerae n. sp.,
A. nudiceps e A. patronus n. sp.), espécies de mandíbula alongada (A. amaris n. sp. e A. yutajae n. sp.) e espécies com
manchas brancas (A. brevifilis, A. leucostictus, A. trinitatis, A. saudades n. sp. e A. triradiatus). As distribuições de An-
cistrus sustentam a hipótese do rio Proto-Berbice, já que A. saudades n. sp. ocorre no alto dos rios Ventuari, Caura e Ca-
roni, que se pensava que uma vez fluiu para o Proto-Berbice. Além disso, embora A. nudiceps não pareça ter se separado
uma vez que o rio Takutu foi capturado pelo Branco, o progenitor de A. leucostictus e A. saudades se dividiu em duas
espécies, pois as populações de cada lado do Portal Rupununi diferem em 7% da sequência do gene mitocondrial Citocro-
mo b. Além das descrições dessas novas espécies, redescrevemos as demais espécies que ocorrem na área e nas bacias
hidrográficas adjacentes. Fornecemos uma chave para a identificação das mesmas e uma hipótese preliminar das relações
filogenéticas baseadas nas sequências de DNA das poucas espécies para as quais estão disponíveis amostras de tecido.
Introduction
Ancistrus is a diverse loricariid genus with 67 valid species and a large number of undescribed species. Male
Ancistrus have a bizarre morphology where the head is adorned with long tentacles (Fig. 1) covered in taste buds
(Ono, 1980); however so is much of the rest of the body, and it is unlikely that taste was a primary factor in tentacle
evolution. Although females do have some tentacles, the extreme development of the tentacles in males suggests
that sexual selection has operated on them. Sabaj et al. (1999) hypothesized that the tentacles act as larval mimics.
Males protect the larvae in the nest until they have absorbed their yolk sacs, and Sabaj et al. speculated that females
prefer males that have larvae in the nest; the tentacles trick the females into thinking the males have larvae in the
nest. Sabaj et al. (1999) further suggested that the tentacles are modifications of the sheaths that produce odontodes
(integumentary teeth) that support the development of the odontodes. The odontodes do not develop in Ancistrus
leaving just the sheaths.
FIGURE 1. Ancistrus nudiceps, lateral and anterior views, AUM 35623, 138.4 mm SL. Photos by M.H. Sabaj.
Ancistrus are fairly common denizens of South American streams, where they have a wide tolerance for
different hydrological conditions. We have collected Ancistrus in a variety of habitats from lowland lakes to high
montane streams. Ancistrus have been demonstrated to be able to breathe air with their stomachs (Kramer et al.,
1983), but they do not have any extensive changes to stomach size or anatomy (Armbruster, 1998).
Despite the very interesting morphology of Ancistrus, a cohesive study on the taxonomy of Ancistrus has not
been completed, with most recent studies being confined to geographic areas (for example, Taphorn et al., 2010,
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ANCISTRUS NORTHWESTERN GUIANA SHIELD ORINOCO ANDES
2013; Provenzano & Barriga-Salazar, 2018) or based on specimens with unique morphologies (for example, Fisch
Muller et al., 2005a,b, de Oliveira et al., 2015, 2016). Poor original descriptions with imprecise locality
information, and damaged, age-worn, or lost type specimens complicates the recognition of already described
species, and hence the description of new ones. In addition, preserved specimens lose many color and pigmentation
patterns observed in live specimens. Compounding issues are that a few names have been applied incorrectly
across the range of Ancistrus, that the type species of the genus (Ancistrus cirrhosus (Valenciennes, 1836)) was
described from an illustrated specimen of unknown provenance and does not have a type; that females were often
originally described in a different genus (Xenocara Regan, 1904); and that even authorities like Eigenmann (1912)
confused species.
We have examined Ancistrus from the northwestern portion of the Guiana Shield (Essequibo and Orinoco
River drainages) and Orinoco Andes. This region contains the type localities for five species of Ancistrus: A.
leucostictus (Günther, 1864), A. lithurgicus Eigenmann (1912), A. macropthalmus (Pellegrin, 1912), A. nudiceps
(Müller & Troschel 1849) and A. triradiatus (Eigenmann, 1918), which also occurs in the Guiana Shield. In
addition we examine here the morphologically similar A. brevifilis Eigenmann, 1920 from the río Tuy of
Venezuela, and A. trinitatis (Günther, 1864) from Trinidad. After examining types, descriptions, and other
specimens, we have determined that each of these species is valid, and that there are an additional six undescribed
species in the region.
This revision also sheds light on biogeographic patterns in the western Guiana Shield. The area was dominated
by the Proto-Berbice paleo-basin, which included parts of the Orinoco, Branco, Essequibo, Courantijne and
Berbice river systems. We examine the prone-8 hydrological hypothesis (Lujan & Armbruster, 2011) in light of
Ancistrus distributions based on morphological and molecular evidence from the mitochondrial Cytochrome b
gene.
Material and methods
Morphological data. Counts and measurements follow Armbruster (2003) with additions by Taphorn et al. (2010).
Plate-row names follow Schaefer (1997). Principal Components Analysis was performed on log-transformed
measurements using JMP ver. 12 (SAS). We excluded tentacle length from the PCA because that character was
found to be uninformative; males’ tentacles gradually develop as they grow, occasionally small males with very
long tentacles and large males with relatively small tentacles can be found, and females have very small or no
tentacles. The sex of specimens was determined by considering the relative width of the naked margin of the snout.
Preadipose plates are the azygous plates located anterior of the adipose-fin spine and were counted from the
posterior dorsal-fin base to the adipose fin spine along the dorsal midline. The dorsal-fin spinelet, first elongate,
unbranched, dorsal ray, and first unbranched pectoral ray were considered spines. Pectoral spine length was
categorized as: short - reaching to just beyond pelvic fin base, medium - reaching to pelvic fin base and cloaca and
long - reaching to or beyond cloaca. Size of Ancistrus is defined as small < 50 mm SL, medium 50 - 80 mm SL and
large > 80 mm SL. Institutional abbreviations follow Sabaj (2017).
We abbreviate meters above sea level as masl, and the median value of meristic ranges as x̃, Dpto. means
Departamento, the equivalent of states in Colombia, Mcpo. means Municipio, roughly equivalent to county. Types
and/or original descriptions of all other species of Ancistrus were examined, and type information is from Ferraris
(2007). Latitude and longitude were determined first from the original records, second from records on Fishnet
(fishnet2.net), and lastly via determining location on Google Maps or Google Earth. For previously described
species and non-type specimens, the number of specimens listed is the number of specimens used for
morphometrics and meristics and a size range of these specimens is given. For new species, the first number given
is the total number of specimens and the second (if needed) is the number examined for morphometrics and
meristics and the size range includes only those specimens (this number may be zero). See Taphorn et al. (2010,
2013) for a list of trans-Andean and Caribbean coast Ancistrus examined. We additionally examined type
photographs on the All Catfishes Species Inventory page (Morris et al., 2006) and all original descriptions).
Molecular data. Our objective was to sequence individuals of Ancistrus and outgroups collected on
expeditions to Venezuela and Guyana from previously published studies (e.g. de Souza et al., 2012). Total genomic
DNA was extracted from fin or muscle tissues and preserved in 95% ethanol in the field. DNA extractions were
made from ethanol-preserved tissues using proteinase K digestion followed by protein precipitation. Nucleic acids
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were precipitated using 95% ethanol chilled to -20˚C. Pellets were washed in 70% ethanol, dried and resuspended
in 20µl of ddH
2
0. One marker was selected from the mitochondrial genome (Cytochrome b) to maximize number
of comparative data. We amplified and sequenced an approximately 1100-bp fragment of the mtDNA spanning the
entire Cytochrome b gene. Primers used were from Hardman (2005): GLU-2 5’-
AACCACCGTTGTTATTCAACTA-3’ and PRO-R1 5’-TAGTTTAGTTTAGAATTCTGGCTTTGG-3’
PCRs for each taxa were conducted in a PTC-100
TM
thermocycler (MJ Research) under the following
conditions: initial denaturing step of 94° C for 3 min, 34 cycles of 94° C for 30s, 45° C for 30s, 72° C for 45s and a
final extension of 72° C for 5 min. Amplifications were visualized via electrophoresing 3mL of PCR product in a
1% agarose gel. Amplified products were sequenced by High-Throughput Genomics Unit (HTGU) genomics
facility at the University of Washington. All sequences were aligned using
SEQUENCHER
4.1.4 (Gene Codes
Corporation, Ann Arbor, MI).
Phylogenetic reconstructions were performed using Maximum Likelihood (ML) inference criteria. The ML
reconstruction was conducted in the program RAxML v. 8.2.10 via the CIPRES portal v. 3.3 (Miller et al., 2010)
under default settings. RAxML searches were performed from several randomly starting seeds to ensure
convergence of likelihood scores. ML nodal support was evaluated using the rapid bootstrapping algorithm.
FIGURE 2. Relevant morphometrics of species of Ancistrus. A. Head length vs. SL for the wide jawed species, A. amaris
(dots) and A. yutajae (circles). B. Principal Components Analysis for the flat species, A. leoni (gray dots), A. lithurgicus (black
dots), and A. macropthalmus (triangles). PC2 was affected most strongly and positively by Dorsal-Pelvic Distance, Snout
Length, and Thorax Length and most strongly and negatively by Head-Eye Length, Interorbital Width, and Head-Pectoral
Length. PC3 was affected most strongly and positively by Premaxillary Tooth Cup Length, Internares Width, and Dorsal-Pelvic
Distance, and most strongly and negatively by Pelvic-Dorsal Distance, Adipose Spine Length, and Adipose-Upper Caudal
Distance. C. PCA of A. kellerae and A. nudiceps by drainage. PC2 was affected most strongly and positively by Eye Length,
Dorsal-Anal Distance, and Dorsal Spine Length, and most strongly and negatively by Interorbital Width, Adipose-Spine
Length, and Orbit Diameter. PC4 was affected most strongly and positively by Adipose-anal Distance, Dorsal-Pelvic Distance,
and Dorsal-Anal Distance, and most strongly and negatively by Dentary Tooth Cup Length, Internares Width, and Premaxillary
Tooth Cup Length. D. Number of Hypertrophied Cheek Odontodes by SL in species of the A. nudiceps group.
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ANCISTRUS NORTHWESTERN GUIANA SHIELD ORINOCO ANDES
FIGURE 3. Dentary Length vs. Cleithral Width for species of the A. triradiatus group.
FIGURE 4. Maximum Likelihood (ML) tree based on model HKY85 as selected by JModeltest and from RAxML analysis.
Constructed from 969bp aligned sites of Cyt b for 34 taxa of Ancistrus from northwestern Guiana Shield.
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Results
Morphometric Variation. Little of mensural importance was found to discriminate the species of Ancistrus. Of
the significant results, A. amaris differed from A. yutajae in head length although there is some overlap in
proportions (Fig. 2A). The three flat species (A. leoni, A. lithurgicus, and A. macropthalmus) separated in a PCA
(Fig. 2B) with A. leoni separating from A. macropthalmus along PC3 and A. lithurgicus separating from A. leoni
and A. macropthalmus along PC2. Ancistrus kellerae separated from A. nudiceps in PCA; however, no distinctions
were found between specimens of A. nudiceps from the Amazon, Essequibo, and Cuyuni (Fig. 2C). Although the
number of cheek odontodes tends to increase with size in most loricariids that have them, in Ancistrus the number
seems fairly stable; however, A. kellerae and A. patronus tend to have higher numbers of cheek odontodes than A.
nudiceps (Fig. 2D) with A. kellerae having 12–17, most A. patronus having 10 or more, and most A. nudiceps
having nine or fewer.
Among the more interesting results is that dentary length varies greatly within the A. triradiatus group (Fig. 3).
Ancistrus triradiatus was broken up by location (Apure, Shield Streams, the Orinoco Delta and neighboring areas,
Guaviare, and the Meta) just to demonstrate the variability. We found that a plot of dentary length vs. cleithral
width separated A. amaris new species from nearly all other specimens in the A. triradiatus group (Fig. 3). In
specimens greater than 69 mm SL, A. amaris has a dentary length/cleithral width ratio of 23.8–28.4% (vs. 14.4–
24.6). Only two specimens of A. triradiatus overlapped A. amaris, and this was due not to having longer dentaries,
but to narrower heads.
Data sequence variation and phylogenetic inference. The final alignment of the protein coding gene
cytochrome b dataset included 969 bp from 34 taxa. There were no ambiguous positions within the
chromatograms. Furthermore, frameshifts or stop codons were absent following translation into amino acids,
suggesting these sequences are not likely pseudogenes. The primary goal for reconstructing the phylogeny of
Ancistrus species based on cytochrome b, was to recover Ancistrus relationships across the Rupununi portal, where
seasonal rains create a temporary hydrological corridor between the Amazon and Essequibo drainages. This
allowed us to determine species boundaries for Ancistrus distributed across this unique biogeographic feature.
Phylogenetic reconstruction resulted in a topology further supporting the genetic variation between Ancistrus
leucostictus in the Essequibo vs. Ancistrus saudades from the Amazon River drainage (Fig. 4). The phylogeny
based on genetics also supports Ancistrus nudiceps distribution across the Rupununi portal. Further, species
clusters are well supported with > 95% for these nodes although there is little support relationship between species.
Key to the species of Ancistrus from the northwestern Guiana Shield, Orinoco Andes, and adjacent
basins
1. No well-defined dark spots on fin spines, fin rays or fin membranes alternating with lighter spots; tiny (the largest usually less
than 1/2 the diameter of the pupil of eye) white, yellow or greenish dots on abdomen, sides, dorsum or fins when alive, usually
lost after some time in preservative in which case they may appear entirely dark . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1’. Spines, rays or membranes of fins with alternating dark and light spots, often arranged in rows; body and/or fins usually (but
not always visible in preserved material) with larger white spots or blotches, some of which are larger than diameter of pupil of
eye . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2. Body dorsoventrally flattened. Eyes placed dorsally or slightly dorsolaterally. Last plate in median series below adipose fin
just slightly taller than wide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2’. Body deep. Eyes placed mostly laterally. Last plate in median series below adipose fin about twice as tall as wide . . . . . . . . . 4
3. Medial section of the interorbital space higher than orbital ridge. Plated area of the snout of nuptial males pointed medially.
Pelvic fin reaching to nearly the end of the anal fin when both fins are adpressed . . . . . . . . . . A. lithurgicus Eigenmann, 1912
3’. Orbital ridge higher than medial section of interorbital space. Anterior border of plated area of the snout of nuptial males
almost straight transversely). Pelvic fin reaching to just barely beyond base of pelvic fin…A. macropthalmus (Pellegrin, 1912)
4. Least interorbital width divided by dentary length less than 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A. yutajae new species
4’. Least interorbital width divided by dentary length greater than 2.25 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Spots only present on head and nape. Edge of caudal fin often broad, gold band. Dark lateral stripe along sides of body with
area above darker than below. Pectoral-fin spine with faint, dark spots. In nuptial males, naked area present posteromedially to
the medial row of tentacles extending to anterior margin of nasal apertures and only a small plate surrounded by flesh between
the nasal aperture and the posteriormost odontodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. kellerae new species
5’. Spots present over the entire body or fins (may be completely absent in preserved specimens). Edge of caudal fin without
broad, gold band. Sides uniformly dark, without lateral stripe. Pectoral-fin spine uniformly dark or with small, gold spots. In
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nuptial males, no naked area present posteromedially to the medial row of tentacles and several plates that abut one another
between posterior tentacle and nasal aperture. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
6. Maximum size 138 mm SL. Snout relatively long and spatulate (Fig. 5a), best visualized in nuptial males where the plated
region of the snout forms a long, rounded triangle such that the distance between the plates and the tip of the snout (turqoise
line in Fig. 5a) is much smaller than the distance between the tip of the plated area and a line drawn between the anterior mar-
gins of the orbits (yellow line in Fig. 5a). Tentacles of the snout bifurcating at the start of the snout plates in a V . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. nudiceps (Müller & Troschel,1849)
6’. Maximum size 86 mm SL. Snout relatively short and rounded (Fig. 5b), best visualized in nuptial males where the plated
region of the snout forms a broad arc and the distance from the plates to the tip of snout (turqoise line in Fig. 5b) is approxi-
mately equal to the distance from the tip of the plates to a line drawn between the anterior margin of the orbits (turqoise line in
Fig. 5b), and tentacles of the snout bifurcating at the start of the snout plates in a U . . . . . . . . . . . . . . A. patronus new species
7. Body dorsoventrally flattened. Eyes placed dorsally or slightly dorsolaterally. Last plate in median series below adipose fin
just slightly taller than wide. Tentacles on medial portion of the snout in nuptial males in a single column. Few white spots
organized in lines down body. Dorsal saddles prominent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A. leoni new species
7’. Body deep. Eyes placed mostly laterally. Last plate in median series below adipose fin about twice as tall as wide. Odontodes
on medial portion of the snout in nuptial males either transversally straight anteriorly or forming a broad triangle. Spots either
absent, few and randomly scattered, or numerous and scattered. Dorsal saddles absent or not very visible . . . . . . . . . . . . . . . . 8
8. Abdomen without spots. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
8’. Abdomen with white spots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
9. Spots on caudal fin not organized, often combining across rows to form very elongate spots, sometimes almost half the length
of the caudal fin and more than twice as long as wide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. brevifilis Eigenmann, 1920
9’. Spots on the caudal fin organized into rows, never combining across rows and never more than twice as long as wide . . . . .10
10. Males with tentacles that are no greater than eye diameter. Dentary length/cleithral width 23.8–28.4% in specimens greater
than 69 mm SL. Minimal interorbital width divided by dentary length less than 2.1. . . . . . . . . . . . . . . . . A. amaris new species
10’. Males with tentacles much greater than eye diameter. Dentary length/cleithral width 14.4–24.6% in specimens greater than 69
mm SL. Minimal interorbital width divided by dentary length usually greater than 2.1. (The only specimens that overlap with
A. amaris do so because of smaller interorbital and cleithral widths, not longer jaws) . . . A. triradiatus Eigenmann 1918 (part)
11. Spots on dorsal fin small and confined to fin rays and not present on membranes (alternating dark and light spots) . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. trinitatis (Günther, 1864)
11’. Large white spots on dorsal fin centered on membranes separated by smaller dark interspaces . . . . . . . . . . . . . . . . . . . . . . . .12
12. Adpressed dorsal fin reaching to at least the middle of the adipose-fin spine. Pectoral-fin spine when adpressed ventral to the
pelvic fin reaching the base of the cloacal tube in adults. Relatively larger light spots and narrower dark interspaces on the
anterolateral plates and posterodorsal head bones with the interspaces much less than half the width of the spots and at least
some spots always visible in this area on preserved specimens (difference generally works on the abdomen as well) . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. leucostictus (Günther, 1864)
12’. Adpressed dorsal fin reaching maximally to middle of preadipose plate. Pectoral-fin spine when adpressed ventral to the pelvic
fin not reaching the base of the cloacal tube in adults. Relatively smaller light spots and larger dark interspaces on the antero-
lateral plates and posterodorsal head bones with the interspaces half or greater than the diameter of the spots and the spots
often obscured in this region in preserved specimens (difference generally works on the abdomen as well) . . . . . . . . . . . . . . 13
13. Spots on head and abdomen small, more than 15 across abdomen in region posterior to pectoral girdle, spots on snouts of
males less than half widths of tentacle bases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. saudades new species
13’. Spots on head and abdomen large, fewer than 12 across abdom en in region posterior to pectoral girdle, spots on snouts of
males almost to greater than widths of tentacle bases. . . . . . . . . . . . . . . . . . . . . . . . . . . . .A. triradiatus Eigenmann, 1918 (part)
Ancistrus amaris new species
(Fig. 6)
Holotype. MCNG 56679 (1, 103.4 mm SL) Venezuela, Estado Portuguesa, Orinoco/Apure drainage, río Las
Marías, 9.402778, -69.7375, J. Alexander, G. Galbreath, A. Seitz, H. López-Fernández, 19-Feb-1998.
Paratypes. All from Orinoco/Apure River Basin, Venezuela. AUM 71043 (2, 63.2–75.2) and MCNG 5280 (2,
64.9–66.1 mm SL) Estado Portuguesa, río Boconó, 9.052778, -70.094444, 2-June-1983, D. Taphorn; CUMV
uncataloged (2, 115.9–107.4) and MCNG 28904 (3, 93.3–115.7 mm SL), Estado Barinas, río La Yuca, 8.766667,
-70.25, 31-Dec-1993, D. Taphorn; AUM 71044 (2, 102.0–106.7 mm SL) and MCNG 41858 (1, 114.9 mm SL)
same data as holotype; MCNG 51925 (1, 71.2 mm SL), Estado Barinas, río Masparro, 8.844651, -70.083963, 23-
Jan-2005, D. Taphorn; INHS 27991 (2, 46.0–113.5 mm SL), Estado Barinas, río Michay, La Esmeralda at Hwy. 5,
8.161762 , -70.870009, 7-Jan-1992, L.Page, B. Burr, P.Ceas, C.Taylor, S. Walsh & A. Barbarino; INHS 31835 (1,
69.9 mm SL) Estado Barinas, río Masparro and río La Yuca (Masparro) 14 km NE of Barinas, 8.77056 , -70.25833
31-Dec-1993, D. Taphorn, L. Page, K.Cummings, C.Mayer, J. Armbruster, C. Laird, M.Sabaj, C. Johnston, S.
Phelps & G. Mottesi; INHS 31858 (2, 105.1–106.4 mm SL) Estado Barinas, río La Yuca (Masparro River drainage)
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17 km NE of city of Barinas, 8.46, -70.15, 31-Dec-1993, D. Taphorn, L. Page, K. Cummings, C. Mayer, J.
Armbruster, C. Laird, M. Sabaj, C. Johnston, S. Phelps & G. Mottesi; INHS 61274 (1, 77.0 mm SL) Estado
Barinas, río Santa Bárbara 3 km NE Santa Barbara, 7.83567, -71.18567, 7-Jan-1992, L. Page, B. Burr, P. Ceas, C.
Taylor, S. Walsh & A. Barbarino-Duque.
FIGURE 5. Heads, dorsal view, of A. Ancistrus nudiceps AUM 35623, 140.2 mm SL and B. A. patronus, holotype, AUM
39876, 83.6 mm SL demonstrating differences in head shape and tentacle pattern. Ancistrus nudiceps has a longer, more
spatulate snout with the point from the edge of medial snout plates to the end of the snout (turquoise line) much shorter than the
distance from the edge of the medial snout plates to a line through the anterior margins of the orbits (yellow line, dashed line is
the line that demarks the anterior borders of the orbits) while the two lengths are approximately equal in A. patronus. In
addition, the anterior margin of the snout plates form a rough V in A. nudiceps and a U in A. patronus (solid white line). Scale
= 1 cm. Photos by J.W. Armbruster.
Diagnosis. Ancistrus amaris differs from all other Ancistrus in the region by having males with very short
tentacles that are all smaller than orbit diameter (vs. some larger than orbit diameter) and from all except A.
patronus and a few specimens of A. triradiatus from the Río Orotoy by having very long dentaries (dentary length/
cleithral width 23.8–28.4% in specimens greater than 69 mm SL and minimal interorbital width divided by dentary
length less than 2.1 vs. usually greater than 2.1 but less than 23.7%; a few specimens overlap, but they do so
because their bodies are narrow and not because their jaws are long). Several described species from the southern
Andean piedmont upper Amazon River Basin tributaries also have long jaws, and A. amaris differs from these (A.
bolivianus (Steindachner 1915), A. bufonius (Valenciennes 1840), A. greeni (Isbrücker 2001), A. heterorhynchus
(Regan 1912), A. marcapatae (Regan 1904), A. megalostomus Pearson 1924, A. occloi Eigenmann 1928 (in Myers
1928), A. sericeus (Cope 1872), and perhaps A. jelksii (Steindachner 1876)) by having the dorsal fin reaching the
preadipose plate (vs. well short), by having the pectoral-fin spine when adpressed below pelvic fin reaching beyond
the pelvic-fin base (vs. barely or not reaching pelvic fin), and by having the body relatively deep (vs. very
depressed). Ancistrus amaris differs from the other long-jawed Ancistrus from rivers of the Guiana Shield (A.
yutajae) by the short snout tentacles mentioned above and by having large light spots and blotches on the body and
fins (vs. with small white dots in unfaded specimens).
Description. Morphometrics in Table 1. A large sized Ancistrus, largest specimen examined 115.7 mm SL.
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Body broadest anteriorly, greatest body width at cleithra, then narrowing progressively to end of caudal peduncle.
Head and body depressed, greatest body depth near posterior margin of supraoccipital. Caudal peduncle deep,
compressed posteriorly. Dorsal profile of head ascending steeply to above eye, then ascending in convex arc to
dorsal-fin origin. From the dorsal-fin origin descending straight or in slightly concave arc to caudal fin. Ventral
profile flat from tip of snout to pelvic-fin insertions, from there, in concave arc to base of caudal fin.
TABLE 1. Morphometric features of Ancistrus amaris n. sp. (N=20) and A. brevifilis (N =13, except
1
N=12).
A. amaris n. sp. A. brevifilis
Feature Avg. SD Min Max Avg. SD Min Max
SL (mm) 90.4 46.0 115.7 74.3 40.4 102.8
% SL
Predorsal Length 47.4 1.5 44.4 50.5 45.5 1.3 42.9 47.8
Head Length 37.4 1.4 34.8 39.8 36.6 1.2 34.5 38.3
Head-dorsal Length 10.4 1.2 7.8 12.6 9.8 1.5 7.7 12.7
Cleithral Width 32.5 0.9 31.1 34.4 31.7 1.8 29.6 35.2
Head-pectoral Length 28.3 1.2 26.1 30.1 28.1 1.9 24.9 31.2
Thorax Length 25.1 1.3 22.5 28.2 23.5 1.4 21.3 26.3
Pectoral-spine Length 30.9 1.8 27.4 34.4 31.4 1.8 27.4 33.5
Abdominal Length 21.9 0.8 20.2 23.1 22.9 2.8 20.7 31.7
Pelvic-spine Length 27.1 1.3 23.5 29.5 26.1 1.4 23.9 27.9
Postanal Length 32.2 0.9 30.6 34.1 32.4 1.2 30.6 34.7
Anal-fin spine Length 11.1 0.9 9.7 12.6 10.3 1.0 8.8 12.2
Dorsal-pectoral Distance 29.7 0.9 27.7 31.6 28.4 1.0 26.3 29.7
Dorsal spine Length 30.7 2.1 26.4 33.6 30.2
1
1.2 28.1 32.3
Dorsal-pelvic Distance 22.8 1.3 19.2 24.6 20.3 1.6 17.6 24.1
Dorsal-fin base Length 24.8 1.5 22.5 30.0 23.0 1.3 21.2 24.8
Dorsal-adipose Distance 15.8 1.6 12.1 18.6 19.0 1.4 17.1 22.1
Adipose-spine Length 8.4 0.8 6.8 10.2 8.3 0.7 7.4 9.9
Adipose-up. caudal Distance 13.5 1.6 11.3 16.5 14.0 1.1 12.4 16.2
Caudal peduncle Depth 12.1 1.3 9.8 14.2 11.0 0.8 10.1 12.1
Adipose-low. caudal Distance 21.2 1.0 19.3 22.9 19.5 2.8 10.4 21.4
Adipose-anal Distance 21.4 1.6 16.1 23.9 20.5 0.9 18.9 21.9
Dorsal-anal Distance 17.1 1.2 15.2 21.3 15.2 2.2 13.5 22.1
Pelvic-dorsal Distance 26.9 1.8 22.2 30.2 23.1 1.6 20.5 25.7
% Head Length
Head-eye Length 38.8 1.9 34.9 41.9 40.6 1.9 36.9 44.3
Orbit Dia. 17.6 1.9 14.5 22.2 17.6 1.6 14.8 20.9
Snout Length 57.7 1.8 54.4 60.9 59.0 2.7 53.1 63.4
Internares Width 18.7 1.1 16.6 20.6 21.6 1.1 20.0 23.7
Interorbital Width 54.2 2.3 50.2 59.5 58.8 2.6 53.5 62.4
Head Depth 65.6 1.9 61.5 69.1 63.9 2.2 60.8 69.0
Mouth Length 47.6 3.0 40.9 53.1 48.7 4.0 42.7 59.3
Mouth Width 61.7 3.5 53.6 67.8 51.1 4.8 44.1 58.6
Barbel Length 5.8 1.5 2.9 8.8 7.2 12.0 1.8 46.9
Dentary tooth cup Length 21.9 2.1 17.2 25.3 15.5 1.5 13.6 18.4
Premaxillary tooth cup Length 22.1 2.0 17.4 24.8 16.8 1.3 14.5 19.0
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FIGURE 6. Holotype of Ancistrus amaris in dorsal, lateral, and ventral views, MCNG 41858, 103.4 mm SL. Scale = 1 cm.
Photos by J.W. Armbruster.
Head wide, interorbital width equal or slightly less than head depth, slightly less than half of head length.
Snout rounded with large broad naked margin in males, less wide in females and juveniles. Snout length more than
one-half head length. Eye moderate in size, interorbital area convex. Oral disk round, just slightly wider than long.
Lips covered with minute papillae, larger near mouth. Lower lip moderate in size, not reaching gill aperture, its
border covered with very small papillae. Maxillary barbel very short, its length less than orbit diameter. Jaws long
with premaxillary tooth rows forming gentle arc and dentary tooth rows forming angle of >135°. Dentary and
premaxillary tooth rows slightly curved medially, most lateral dentary tooth lateral to most lateral premaxillary
tooth. Teeth numerous (58–120 per jaw ramus), asymmetrically bifid, medial cusp larger and spatulate, lateral cusp
smaller, pointed, usually not reaching more than half length of medial cusp but variable, almost equal in worn teeth.
Hypertrophied cheek odontodes strongly evertible, nine to 17, stout with tips hooked anteriorly, bases encased in
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thick fleshy sheaths. Exposed part of opercle small, roughly triangular with larger odontodes along free edge. Head
without conspicuous ridges, bones on back of head not carinate; supraoccipital with margins between surrounding
bones and plates usually clearly visible. Lateral plates not carinate, lateral line pores not easily visible except
anteriorly.
Ventral surface of head and abdomen naked, no exposed platelets anterior to anal-fin spine. Nuchal plate small
and curved posterolaterally. Odontodes enlarged along edges of lateral plates. Five series of lateral plates
anteriorly, three series on caudal peduncle, mid-dorsal plate series variable in length, often ending below third or
fourth plate posterior to dorsal-fin base; mid-ventral plate series usually to preadipose plate or adipose spine. Last
plate in median series about same size as penultimate plate, and median plate below end of adipose fin about twice
as high as wide. Base of caudal fin with up to six small platelets covering bases of caudal-fin rays. Dorsal-fin origin
situated slightly anterior to vertical through pelvic-fin insertion. First dorsal-fin ray elongate, longer than snout
length nearly as long as head; last dorsal-fin ray reaching first preadipose plate when depressed. Adipose-fin spine
curved, stout, not embedded, oriented at angle to horizontal axis of body, membrane present, easily visible beneath
spine. Pectoral spine long and stout, when adpressed ventrally reaching between posterior margin of pelvic-fin
bases and the cloaca. Anal fin small but well developed; first anal-fin pterygiophore covered by skin, its origin well
posterior to vertical through base of last dorsal-fin ray. Pelvic fins reaching well past anal-fin origin, about halfway
out length of fin, inserted posterior to vertical through base of first branched dorsal-fin ray. Caudal fin truncate,
lower lobe longer than upper. Tiny odontodes present on body plates, largest on posterior margins of plates. All fin
spines with small odontodes, more developed in pectoral-fin spine of males. All fin rays with tiny odontodes on
rays.
Meristics (N=20). mid-ventral plates 16–19, x̃ 18; median plates 22–24, x̃ = 23; mid-dorsal plates 10–18, x̃
=13; plates bordering dorsal-fin base four to eight, x̃ = seven; plates between dorsal and adipose fins four to eight,
x̃ = seven; preadipose plates one to two, x̃ = one. Fin-ray formulae: dorsal II,7; pectoral I,6; pelvic i,5; anal i,3–4, x̃
= i,4; caudal i,14,i. Caudal procurrent spines: dorsal: four to five, x̃ = five; ventral: three to four, x̃ = three.
Sexual dimorphism. Snout tentacles of nuptial males short, longest less than eye diameter. Posteromedial
tentacles diverging in V-shape along anteriorly triangular snout plates. Naked areas of snout without tentacles not
rugose, separated from naris by several wide plates.
FIGURE 7. Distribution of species of Ancistrus from the northwestern Guiana Shield and neighboring regions.
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Color in alcohol. (Fig. 6) Dorsum of body base color light brown with medium-sized white spots on plateless
area of snout, head and body. Males with relatively short tentacles on snout. Spines of dorsal, pectoral, pelvic,
adipose and caudal fins with five or six alternating light and dark sections with similar markings mirrored on all fin
rays, to form rows of dark and light spots. Spines of pectoral and pelvic fins darker overall. Ventral surface of head
and abdomen tan to yellowish tan with no spots, oral disk yellow, plates on ventral surface of caudal peduncle with
posterior margins dark brown, forming alternating light and dark pattern.
Life colors. Color in life unknown.
Distribution. Known from Andean piedmont streams of the Río Apure/Río Orinoco drainage of Venezuela
(Fig. 7).
Etymology. From the Latin maris for masculine or virile and the prefix a meaning without. In reference to the
short tentacles in nuptial males.
Ancistrus brevifilis Eigenmann 1920
(Fig. 8)
Ancistrus brevifilis Eigenmann, 1920: 7, pl. 1. Type locality: El Concejo, río Tiquirito [Tuy River Basin of Caribbean coast],
Venezuela. Holotype: CAS 64609.
Specimens examined. All from Venezuela, Tuy River Basin. CAS 64610 (paratypes, 2, 73.3–102.0 mm SL)
Aragua State, Tiquirito River at El Concejo, tributary of the Tuy River, 2040 masl, 10.24018, -67.26484. MCNG
14095 (1, 68.9 mm SL), Miranda State, District Guicaipuro, Guiare de Tácata River, approximately 5 km upriver of
Tácata, 10.21274, 67.00551, 30-Jul-1985, D. Taphorn. MCNG 14304 (3, 61.2–68.0 mm SL) Miranda State, bridge
near Araguita al Sur, District Acevedo, 10.21737, -66.45007, 29-Jul-1985, D. Taphorn. FMNH 84621 (6, 44.0–
102.8 mm SL), (ex MBUCV 2757), Miranda State, Guira River, 24-Apr-1966, F. Mago-L., & J. Moscó.
Diagnosis. Ancistrus brevifilis can be separated from all other Ancistrus in the region by having elongate light
spots in the overall dark caudal fin with the spots irregular and often fusing with spots from other rows (vs. spots
generally minuscule and usually lost in preservation or large, but round to only about twice as long as high and
arranged relatively uniformly on the fin and not combining across rows); and from A. leucostictus and A. saudades
by always lacking spots on the abdomen (vs. spots present).
Description. Morphometrics in Table 1. A large Ancistrus, largest specimen examined 103 mm SL. Body
broadest anteriorly, greatest body width just posterior to opercles, then narrowing progressively to end of caudal
peduncle. Head and body depressed, greatest body depth just anterior to dorsal-fin origin. Caudal peduncle deep,
compressed posteriorly. Dorsal profile of head ascending at about a 45 degree angle to above eye, then ascending in
shallow convex arc to dorsal-fin origin; from there descending straight or in slightly concave arc to caudal fin.
Ventral profile flat from tip of snout to pelvic-fin insertions, from there, in concave arc to base of caudal fin;
abdomen slightly concave or convex depending on fullness of intestines.
Head wide, interorbital width less than head depth, less than half of head length. Snout rounded with large
broad naked margin in males, less wide in females and juveniles. Snout length more than one-half head length. Eye
small, interorbital area convex. Oral disk round, just slightly wider than long. Lips covered with minute papillae,
larger near mouth. Lower lip moderate in size, not reaching gill aperture, its border covered with very small
papillae. Maxillary barbel very short, its length less than orbit diameter. Jaws short with premaxillary tooth rows
forming strong arc and dentary tooth rows forming angle of ≤135°. Dentary and premaxillary tooth rows strongly
curved medially, lateralmost dentary tooth medial to lateralmost premaxillary tooth. Teeth numerous (43–105 per
jaw ramus), asymmetrically bifid, medial cusp larger and spatulate, lateral cusp smaller, pointed, usually not
reaching more than half length of medial cusp but almost equal in worn teeth. Hypertrophied cheek odontodes
strongly evertible, 11–14, stout with tips hooked anteriorly, bases encased in thick fleshy sheaths. Exposed part of
opercle small, roughly triangular with larger odontodes along free edge. Head smooth, bones on back of head not
carinate; supraoccipital with margins between surrounding bones and plates usually clearly visible. Lateral plates
not carinate, lateral line pores not easily visible.
Ventral surface of head and abdomen naked, no exposed platelets anterior to anal-fin spine. Nuchal plate small
and curved posterolaterally. Odontodes enlarged along edges of lateral plates. Five series of lateral plates
anteriorly, three series on caudal peduncle, mid-dorsal plate series variable in length, usually ending below first
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preadipose plate; mid-ventral plate series usually one plate longer than mid-dorsal series, ending under adipose
spine. Last plate in median series about same size as penultimate plate, and median plate below end of adipose fin
about twice as high as wide. Base of caudal fin with vertical column of four square platelets and six to eight
triangular platelets covering bases of caudal-fin rays.
FIGURE 8. Ancistrus brevifilis in dorsal, lateral, and ventral views, MCNG 14304, 61.2 mm SL. Scale = 1 cm. Photos by J.W.
Armbruster.
Dorsal-fin origin situated slightly anterior to vertical through pelvic-fin insertion. First dorsal-fin ray not
elongate, much longer than snout length, nearly as long as head; last dorsal-fin ray reaching first preadipose plate
when depressed. Adipose-fin spine straight, stout, not embedded, oriented at angle to horizontal axis of body,
membrane present, easily visible beneath spine. Pectoral spine long and stout, when adpressed ventrally reaching
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between posterior margin of pelvic-fin bases and the cloaca, which we categorize as medium length. Anal fin small
but well developed; first anal-fin pterygiophore covered by skin, its origin well posterior to vertical through base of
last dorsal-fin ray. Pelvic fins reaching well past anal-fin origin, about halfway out length of fin, inserted posterior
to vertical through base of first branched dorsal-fin ray. Caudal fin truncate, lower lobe longer than upper. Tiny
odontodes present on all fin rays and body plates, largest on posterior margins of plates. All fin spines with small
odontodes, more developed in pectoral-fin spine of males.
Meristics (N=13). mid-ventral plates 17–19, x̃ =17; median plates 22–23, x̃ = 22; mid-dorsal plates 16–19, x̃
=17; plates bordering dorsal-fin base six to seven, x̃ = six; plates between dorsal and adipose fins six to seven, x̃ =
six; preadipose plates one to two, x̃ = one. Fin-ray formulae invariable: dorsal II,7; pectoral I,6; pelvic i,5; anal i,4;
caudal i,14,i. Caudal procurrent spines: dorsal: five; ventral: two to five, x̃ = four.
Sexual dimorphism. Snout tentacles of nuptial males long, largest over twice eye diameter. Posteromedial
tentacles diverging in V-shape along anteriorly triangular snout plates. Naked areas of snout without tentacles
rugose, separated from naris by several wide plates; naked area wide, distance from anteromedial plate to snout
greater than distance from anteromedial plate to line formed between anterior edges of nasal apertures.
Color in alcohol. From Eigenmann’s (1920:8) original description: “Dorsal, caudal, ventrals and pectorals,
each with four or five conspicuous, wavy bars; faint darker spots about the size of the eye in front of the dorsal,
ventral surface uniform. In the female, the smaller paratype, the number of bands is smaller and they are less well
marked”. In general, tan in alcohol, with lighter whitish abdomen. Fins dark with large light, irregular, and
sometimes horizontally elongate spots, that are centered on fin rays, especially noticeable on caudal fin with some
spots combining across rows to make wavy lines as noted by Eigenmann. Spines of the dorsal, adipose, caudal,
pelvic and pectoral fins with four to six alternating dark and light sections, mirrored on the branched rays, with
dark and lighter areas also extending onto membranes. Dorsum and sides of body often faintly marked with traces
of dark saddles and plates often two-toned with dark and light brown sections, forming mottled appearance (Fig. 8).
Life colors. Based on photographs from Mr. Shane Linder on PlanetCatfish.com of specimens said to be from
Tuy River drainage. Base color black and gray on dorsum, and all fins. Body mostly gray with rows of darker gray
to black spots forming horizontal rows to upper sides and dorsum. Fins two-toned, gray and black. Dorsal fin edged
in gray, with two to three rows of alternating black and gray spots, not really aligning to form lines; adipose spine
gray with black spot; caudal fin with dark background and light gray spots, some aligning to form vertical rows and
some combining across rows. Top of head and most barbels black. Ventrum of head and body light gray.
Distribution. Known only from the Río Tuy that drains into the Caribbean Sea of Venezuela (Fig. 7).
Comments. Ancistrus brevifilis is very similar to A. triradiatus, but is generally brighter in color and has more
intense spotting on the caudal fin than A. triradiatus from Venezuelan Andean streams.
Ancistrus kellerae new species
(Figs. 9–10).
Holotype. CSBD F 1721 (1, 69.9 mm SL) Guyana, Region 8 (Potaro/Siparuni), Potaro River drainage, Kuribrong
River, in rapids at Grass Shoals, 5.40791, -59.53179, 12-Mar-2014 J. Armbruster, D. Werneke, E. Liverpool, D.
Fernandes, and D. Taphorn.
Paratypes. AUM 62849 (1, 55.0 mm SL) collected with holotype; FMNH 135052 (1, 50.1 mm SL) collected
with holotype.
Diagnosis. Ancistrus kellerae can be separated from all species in the region except A. patronus by having a
naked area posteromedial to the medial row of tentacles extending to anterior margin of nasal apertures (area is
triangular in A. kellerae, rectangular in A. patronus, and absent in all other species), and by having only a small
plate surrounded by flesh between the nasal aperture and the posteriormost odontodes (vs several plates that abut
one another); from A. patronus by having a short dentaries (11.6–12.5% vs. 20.3–29.1% HL); and from the most
similar species, A. nudiceps, by usually having a broad golden edge of the end caudal fin (vs. a narrow line
maximally), by having gold spots only on the head (vs. all over), by having a dark lateral stripe (vs. entirely black),
by being darker dorsally along sides than ventrally (vs. uniform color), and by having faint dark spots along the
pectoral-fin spine (vs. black with small gold to white spots).
Description. Morphometrics in Table 2. A small-sized Ancistrus; size range of examined specimens 50.1–69.9
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mm SL. Body broadest anteriorly, greatest body width just posterior to opercles, then narrowing progressively to
end of caudal peduncle. Head and body depressed, greatest body depth between level of pectoral-fin insertions and
dorsal-fin origin. Caudal peduncle deep, robust, compressed posteriorly. Dorsal profile of head ascending steeply
in convex arc from tip of snout to just posterior of orbits, ascending in straight line to posterior tip of supraoccipital,
then descending to dorsal-fin origin. From the dorsal-fin origin descending in a slight convex arc to just posterior
of dorsal-fin base, then straight to caudal fin. Ventral profile flat to slightly convex from tip of snout to pelvic-fin
insertions. Abdomen flat to slightly concave to pelvic-fin insertions, from there, straight to slightly convex and
sloping gently ventrally towards caudal fin.
Head wide, interorbital width equal or slightly less than head depth, slightly less than half of head length.
Snout rounded with large broad naked margin in males, less wide in females and juveniles. Snout length about one-
half head length. Eye moderate in size, interorbital area slightly convex. Oral disk ovate, wider than long. Lips
covered with minute papillae, larger near mouth. Lower lip moderate in size, not reaching gill aperture, its border
covered with very small papillae. Maxillary barbel very short, its length less than orbit diameter. Jaws short with
premaxillary tooth rows forming strong arc and dentary tooth rows forming angle of ≤135°. Dentary and
premaxillary tooth rows strongly curved medially, lateralmost dentary tooth medial to most lateral premaxillary
tooth. Teeth numerous, but fewer than in many Ancistrus (36–44 per jaw ramus), asymmetrically bifid, medial cusp
much larger and spatulate, lateral cusp minute and pointed, usually not reaching more than half length of medial
cusp, equal in worn teeth. Hypertrophied cheek odontodes strongly evertible, 12–17, stout with tips hooked
anteriorly, bases encased in thick fleshy sheaths. Exposed part of opercle small, roughly triangular with larger
odontodes along free edge. Head smooth, bones on back of head not carinate; supraoccipital with margins between
surrounding bones and plates usually clearly visible. Lateral plates not carinate, lateral line pores readily visible
anteriorly, but not posteriorly.
Ventral surface of head and abdomen naked, no exposed platelets anterior to anal-fin spine. Nuchal plate small
and curved posterolaterally. Odontodes enlarged along edges of lateral plates. Five series of lateral plates
anteriorly, three series on caudal peduncle, mid-dorsal and mid-ventral plate series ending on caudal peduncle
beneath preadipose plate just anterior to embedded adipose-fin spine. Last plate in median series slightly smaller
than penultimate plate, and median plate below end of adipose fin about twice as high as wide. Base of caudal fin
with six platelets covering bases of caudal-fin rays. Dorsal-fin origin situated anterior to vertical through pelvic-fin
insertion. First dorsal-fin ray not elongate, just slightly longer than snout length; last dorsal-fin ray reaching first
preadipose plate when depressed. Adipose-fin spine not embedded, oriented at an angle horizontal to axis of body,
membrane visible beneath spine. Pectoral spine short and stout, when adpressed ventrally reaching to the insertion
of the pelvic fin, which we categorize as minimum distance (short). Anal fin small but well developed; base of first
anal-fin pterygiophore covered by skin, its origin below or posterior to vertical through base of last dorsal-fin ray.
Pelvic fins reaching well past anal-fin origin, inserted posterior to vertical through first branched dorsal-fin ray.
Caudal fin truncate, lower lobe slightly longer than upper.
Tiny odontodes present on body plates, largest on posterior margins of plates. All fin spines with small
odontodes, more developed in pectoral-fin spine of males. All fin rays with tiny odontodes on rays.
Meristics (N=3). mid-ventral plates 16–17, x̃ = 17; median plates 22–23, x̃ = 22; mid-dorsal plates 15; plates
bordering dorsal-fin base six; plates between dorsal and adipose fins five; preadipose plates one. Fin-ray formulae
(N=3): dorsal II,7; pectoral I,6; pelvic i,5; anal i,3–4, x̃ = i,4; caudal i,14,i. Caudal procurrent spines: dorsal: four to
five, x̃ = five; ventral: three to four, x̃ = four.
Sexual dimorphism. Snout tentacles of nuptial males long, largest over twice eye diameter. Posteromedial
tentacles diverging in V-shape along anteriorly triangular snout plates, but anterior plates covered by thick flesh.
Naked areas of snout without tentacles rugose, separated from naris by single, thin plate; naked area wide, distance
from anteromedial plate to snout greater than distance from anteromedial plate to line formed between anterior
edges of nasal apertures.
Color in alcohol. (Fig. 9) Dorsal and lateral base color dark gray or brown mottled with light brown spots on
top of head and body. Dark line present along midline, body darker above than below. Plateless area of snout and
tentacles also dark with irregular lighter spots. Pectoral and pelvic fins with at least faint alternating dark and light
spots. Dorsal and caudal fins uniform dark brown color. Pale whitish band on the tip of the caudal fin. Ventral
surface of head and abdomen tan to yellowish tan, oral disk yellowish, plates of ventral surface of caudal peduncle
with posterior margins darker brown, forming alternating light and dark pattern.
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TABLE 2. Morphometric features of Ancistrus kellerae n. sp. (N=3) and A. leoni (N =6).
Life colors. (Fig. 10) Dorsum mottled dark and light brown with small yellowish spots concentrated on
plateless area of snout, tentacles and top of head. Body posterior to dorsal-fin origin with fewer spots, and base
color is dark and light brown. Preadipose plate and adipose-fin spine outlined in yellow. Sides with irregular light
and dark spots. Body posterior of insertion of dorsal and pelvic fin coloration dorsally is dark brown and lighter
brown ventrally, appearing to have a dark median horizontal line along the middle of body to caudal fin. Ventrum
A. kellerae n. sp. A. leoni n. sp.
Feature Avg. SD Min Max Avg. SD Min Max
SL (mm) 58.3 50.1 69.9 55.2 44.9 81.6
% SL
Predorsal Length 48.2 1.7 46.5 50.0 46.4 1.3 44.6 48.1
Head Length 37.6 3.3 33.9 40.3 38.7 1.1 37.4 40.3
Head-dorsal Length 10.2 1.5 8.5 11.4 8.3 0.7 7.4 9.4
Cleithral Width 30.0 1.3 28.8 31.4 32.5 0.8 31.9 33.7
Head-pectoral Length 28.7 1.4 27.6 30.3 31.1 1.9 29.6 34.7
Thorax Length 26.5 1.0 25.5 27.4 22.5 1.3 20.6 23.6
Pectoral-spine Length 31.5 1.5 30.6 33.2 27.8 1.4 26.1 29.9
Abdominal Length 23.0 1.3 22.1 24.5 22.7 1.2 20.5 23.8
Pelvic-spine Length 25.5 2.2 23.6 27.9 24.8 0.8 23.6 26.0
Postanal Length 29.4 2.0 27.5 31.5 31.0 0.9 29.6 32.5
Anal-fin spine Length 8.6 0.2 8.5 8.8 9.6 0.9 8.2 10.4
Dorsal-pectoral Distance 29.3 2.2 27.7 31.7 26.7 0.6 26.1 27.6
Dorsal spine Length 23.1 2.1 21.3 25.5 24.3 1.1 23.3 25.9
Dorsal-pelvic Distance 20.7 1.9 19.4 22.9 16.3 1.2 14.9 18.3
Dorsal-fin base Length 21.0 0.7 20.4 21.8 22.0 0.9 20.8 23.2
Dorsal-adipose Distance 17.6 1.1 16.5 18.8 15.9 1.7 12.6 17.4
Adipose-spine Length 7.3 0.7 6.7 8.1 8.0 1.2 6.8 10.3
Adipose-up. caudal Distance 13.8 1.2 12.5 15.0 14.2 0.8 12.8 15.2
Caudal peduncle Depth 9.4 0.7 8.7 10.1 8.1 1.0 7.0 9.3
Adipose-low. caudal Distance 17.8 1.5 16.8 19.5 19.3 1.2 18.5 21.7
Adipose-anal Distance 17.0 0.7 16.3 17.7 17.4 0.8 16.1 18.3
Dorsal-anal Distance 14.9 0.5 14.4 15.4 12.2 0.9 11.3 13.9
Pelvic-dorsal Distance 23.8 1.3 22.9 25.3 22.6 1.1 21.3 24.3
% Head Length
Head-eye Length 40.3 2.5 37.8 42.7 33.6 1.9 30.3 36.2
Orbit Dia. 19.7 3.0 16.6 22.6 17.5 1.7 14.6 19.5
Snout Length 60.5 1.9 58.4 61.8 61.1 1.4 58.7 62.7
Internares Width 20.3 0.3 20.0 20.6 18.2 1.5 16.9 21.1
Interorbital Width 56.7 3.2 53.0 59.0 49.9 1.6 47.8 51.8
Head Depth 63.6 2.5 61.2 66.2 58.6 2.5 55.7 62.8
Mouth Length 48.4 2.9 45.5 51.3 54.8 3.4 50.2 58.6
Mouth Width 55.3 5.1 50.0 60.3 57.9 3.3 52.0 60.9
Barbel Length 5.4 1.2 4.3 6.6 4.5 2.1 3.2 8.8
Dentary tooth cup Length 12.2 0.5 11.6 12.5 15.9 1.3 13.5 17.2
Premaxillary tooth cup Length 14.7 1.1 13.9 15.9 17.0 1.0 15.7 18.2
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of body lighter than sides, and mottled (from what can be viewed in Fig. 10). Oral disk and adjacent area on chest
cream. Fin membranes lightly pigmented, grayish, but spines and rays tan in color with spots on pectoral and pelvic
fins. Caudal-fin spine and rays uniform in color except for a white band vertically along the tip.
FIGURE 9. Holotype of Ancistrus kellerae in dorsal, lateral, and ventral views, CSBD F 1721, 69.9 mm SL. Scale = 1 cm.
Photos by J.W. Armbruster.
Distribution. Known only from the type locality in the Kuribrong River, Potaro River - Essequibo River
drainage (Fig. 7). The locality is below Amaila Falls.
Etymology. Named in honor of Connie Keller and in gratitude for her leadership as Chair of the Board of
Trustees for the Field Museum, where her unparalleled support of research and conservation work has led to the
protection of more than 8 million hectares of South America forests and rivers. Lead author is personally inspired
and honored to share a love of fly-fishing, the outdoors and conservation with Connie.
Comments. The Kuribrong River is under dramatic pressure from gold and diamond mining, and Hardman et
al. (2002) noted a decrease in loricariids in the mainstem Potaro River compared to what Eigenmann (1912) found
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likely due to the mining there in 1998. Grass Shoals is the last rapids upstream before the base of Amaila Falls. It is
a clear-flowing section of stream with ample rooted vegetation. Little mining was present this far up in the drainage
at time of collection, but a recently completed road to the base of Amaila Falls will likely lead to increasing mining
pressure from Grass Shoals to above the escarpment.
FIGURE 10. Live coloration of the holotype of Ancistrus kellerae in dorsal and lateral views, CSBD F 1721, 69.9 mm SL.
Scale = 1 cm. Photos by J.W. Armbruster.
Ancistrus leoni, new species
(Figs. 11–12)
Holotype. MCNG 56680 81.6 mm SL, (ex MCNG 53811), Venezuela, Amazonas State, Atabapo District, Río
Negro, in rapids about 1 km south (downstream) of the mouth of the Casiquiare, 1.987611, -67.120250, 2-Feb-
2005, O. León Mata, K. Redden, R. Williams.
Paratypes. Venezuela, Amazonas State. MCNG 53811 (2) same data as holotype; AUM 43265 (2, 0), Orinoco
River 147 km ESE of San Fernando de Atabapo, 3.30662, -66.603, 4-Mar-2004, N. Lujan, M. Sabaj, M. Arce, T.
Wesley; AUM 42972 (4, 2, 53.6–59.9 mm SL), Orinoco River at Puerto Venado, 4.3 km S of Samariapo, 56.4 km
SSW of Puerto Ayacucho, 5.21060, -67.80495, 26-Feb-2005, N. Lujan, D. Werneke, M. Sabaj, M. Arce, R.
Betancur, T. Wesley; AUM 43665 (5, 4, 44.9–49.3 mm SL), Casiquiare River, left bank upstream from mouth of
Siapa River, 2.15570, -66.46377, 19–22-Mar-2005, N. Lujan, M. Arce, T. Wesley, G. Santaella; AUM 53527 (1,
55.0 mm SL), Orinoco River at Pasaganado, 38 km NNW of San Fernando de Atabapo, 4.38418, -67.77473, 27-
Mar-2010 N.Lujan, D. Werneke, M. Sabaj, T. Carvalho, V. Meza, O. León Mata. Brazil, Amazonas state: CAS-SU
56890 (2, not measured), rio Negro, São Gabriel rapids, -0.138826, -67.088998, 1-Feb-1925, C. Ternetz.
Diagnosis. Ancistrus leoni can be separated from all other Ancistrus in the region by having the odontodes
located medially on the snout in a single, narrow column (vs. a broad triangular, curved, or rectangular area) and by
having a color pattern consisting of small white spots and well-developed dorsal saddles (vs. many smaller white or
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yellow spots packed more closely together or just on head, large white spots, or entirely brown sides and saddles
weakly developed if present); and from all except A. macrophthalmus by having the eyes almost completely
dorsally located on the head and the orbital rim the most elevated portion of head (vs. eyes slightly dorsally placed
in A. lithurgicus and mostly lateral in all other species and with the medial interorbital point more dorsal than the
orbital rim). The nuptial male A. leoni is the only Ancistrus we examined with a tentacle located in an area between
the posteromedial and cheek sections (all other Ancistrus have the tentacles absent from an area medial to the nasal
aperture and the base of the evertible cheek odontodes). Ancistrus leoni also differs from A. macrophthalmus and A.
lithurgicus by having a very light ventral surface (vs. ventral surface only slightly lighter than black sides).
Description. Morphometrics given in Table 2. Size range of examined specimens: 45–60 mm SL. A medium-
sized Ancistrus, greatest body width just posterior to opercles, then narrowing progressively to end of caudal
peduncle. Head and body flat, very depressed, greatest body depth at level of pectoral-fin insertions. Caudal
peduncle of moderate depth, greatly compressed posteriorly. Dorsal profile of head almost straight, ascending in
slightly convex arc from snout tip to dorsal-fin origin then in straight line to posterior margin of adipose fin, angled
slightly up to caudal fin. Ventral profile flat to pectoral-fin insertions, abdomen slightly concave to pelvic-fin
insertions, from there, straight to slightly convex to vertical through dorsal caudal-fin spine, then sloping gently
ventrally towards ventral caudal-fin spine, which is offset and posterior to dorsal caudal-fin spine.
Head wide, interorbital width greater than head depth, equal or slightly more than half of head length. Snout
long and somewhat pointed, narrowly rounded with moderate naked margin in males, less wide in females and
juveniles. Snout very elongate its length much more than half head length. Eye moderate in size, interorbital area
flat to slightly concave. Oral disk almost round, only slightly wider than long. Lips covered with minute papillae,
larger near mouth. Lower lip moderate in size, not reaching gill aperture, its border covered with very small
papillae. Maxillary barbel very short, its length less than orbit diameter. Jaws moderate with premaxillary tooth
rows forming strong arc and dentary tooth rows forming angle of >135°. Dentary and premaxillary tooth rows
slightly curved medially, lateralmost dentary tooth medial to lateralmost premaxillary tooth. Teeth numerous, but
less so than many Ancistrus, (44–58 on dentary, 47–62 on premaxillary), asymmetrically bifid, medial cusp much
larger and spatulate, lateral cusp smaller, usually not reaching more than half length of medial cusp, equal in worn
teeth. Hypertrophied cheek odontodes strongly evertible, eight to 13, stout with tips hooked anteriorly, bases
encased in thick fleshy sheaths. Exposed part of opercle small, roughly triangular with large patch of odontodes.
Head smooth, bones on back of head not carinate; supraoccipital with margins between surrounding bones and
plates usually clearly visible. Lateral plates with enlarged odontodes but not carinate, lateral line complete, pores
not always readily visible.
Ventral surface of head and abdomen naked, no exposed platelets anterior to anal-fin spine. Nuchal plate small
and curved posterolaterally. Enlarged odontodes present forming keel on posterior, ventral plates of caudal
peduncle. Five series of lateral plates anteriorly, three series on caudal peduncle, middorsal plate series ending on
caudal peduncle beneath preadipose plate just anterior to embedded adipose-fin spine; mid-ventral plate series
extending more posteriorly, ends on caudal peduncle beneath anterior part of adipose-fin spine. Last plate in
median series same size as penultimate plate, and median plate below end of adipose fin just slightly higher than
wide. Base of caudal fin with six or seven smaller platelets covering bases of caudal-fin rays.
Dorsal-fin origin situated slightly anterior to vertical through pelvic-fin insertion. First dorsal-fin ray not
elongate, just slightly longer than snout length; last dorsal-fin ray just reaching first preadipose plate when
depressed. Adipose-fin spine oriented at 30–40 degree angle to horizontal axis of body, membrane light near spine,
dark near body, easily visible. Pectoral spine short, reaching past pelvic-fin insertions but only to anterior third of
pelvic fins. Anal fin small but well developed; base of first anal-fin pterygiophore covered by skin, anal-fin origin
posterior to vertical posterior edge of dorsal-fin base. Pelvic fins reaching well past anal-fin origin, inserted
posterior to vertical through first branched dorsal-fin ray. Caudal fin margin truncate, lower lobe slightly longer
than upper, its base at angle to body’s horizontal axis, with upper spine insertion anterior to that of lower.
Tiny odontodes present on body plates, largest on posterior margins of plates. All fin spines with small
odontodes, more developed in pectoral-fin spine of males. All fin rays with tiny odontodes on rays.
Meristics (N=6). Mid-dorsal plates 16–18, x̃ = 16; median plates 22–24, x̃ = 23; mid-ventral plates 17–18 x̃ =
18; plates bordering dorsal-fin base seven to eight, x̃ = eight; plates between dorsal and adipose fins six to seven, x̃
= six; preadipose plates: one. Fin-ray formulae invariable: dorsal II,7; pectoral I,6; pelvic i,5; anal i,4; caudal i,14,i.
Caudal procurrent spines: dorsal: four to five, x̃ = five; ventral: three to four, x̃ = three.
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FIGURE 11. Holotype of Ancistrus leoni in dorsal, lateral, and ventral views, MCNG 53811, 81.6 mm SL. Scale = 1 cm.
Photos by J.W. Armbruster.
Sexual dimorphism. Snout tentacles of nuptial males short, largest approximately same length as eye
diameter. Posteromedial tentacles diverging in narrow V-shape along anterior single row of snout plates,
posteromedial tentacles very short. Naked areas of snout without tentacles rugose, separated from naris by several
wide plates; one small tentacle located between posteromedial and cheek sections of tentacles; naked area narrow,
distance from anteromedial plate to snout less than distance from anteromedial plate to line formed between
anterior edges of nasal apertures.
Color in alcohol. (Fig. 11) Dorsum of body base color tan with well-separated white spots on plateless area of
snout, head and body and five faint, wide brown saddles. White spots relatively larger in smaller specimens.
Opercle and sides of head, body and caudal peduncle also tan or light brown with white spots as on dorsum. Spines
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and rays of fins with alternating light and dark sections, membranes translucent clear or light gray. Oral disk and
ventral surfaces of head and abdomen white, lower lip in some smaller specimens with narrow gray edges. Ventrum
of caudal peduncle lighter tan than sides, without white spots. Some specimens with pigment pattern mostly faded
to varying degrees of brown, with light spots not visible.
FIGURE 12. Live coloration of the holotype of Ancistrus leoni in dorsal and lateral views, MCNG 53811, 81.6 mm SL. Scale
= 1 cm. Photos by N.K. Lujan.
Life colors. (Fig. 12) Dorsum brown to olive brown with five darker brown to blackish saddles peppered with
white, cream or light greenish to yellowish spots (most about one fifth to one fourth orbit diameter in size, a few
larger) on plateless area of snout, top of head and entire length of body. Spots on head more numerous, smaller and
closer together on top of head than on dorsum of body. Sides of head and body light brown with white spots; lower
half of body posterior to pelvic-fin insertions lighter brown than top half. Ventrum of head and body white. Oral
disk and adjacent area on chest white. Fin membranes gray, without light or dark spots, but spines and rays marked
with two to five alternating dark and light sections (the longer ones with more). Caudal-fin spine and rays with
alternating light and dark sections often aligned to form irregular vertical rows or arcs, with the dark sections much
wider than the light.
Distribution. The upper río Negro and río Orinoco in Amazonas state of Venezuela, northernmost Brazil and
probably tributaries of the río Negro in adjacent regions of Colombia (Fig. 7).
Etymology: Named to honor our fallen colleague, Ing. RNR Oscar León Mata (1964-2018), who collected the
holotype and dedicated much of his too-short life to Venezuelan ichthyology. Oscar collected the type series of this
new species and was invaluable during many of the expeditions to Venezuela, which would not have succeeded
without him. He is sorely missed by his family and friends.
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Ancistrus leucostictus (Günther 1864)
(Fig. 13)
Chaetostomus leucostictus Günther, 1864: 248. Type locality: Essequibo [Guyana]. Possible holotype: BMNH 1864.1.21.85
(type designation questioned by Muller, 1989 and Fisch-Muller, 2003).
Specimens examined. Guyana, Essequibo/Rupununi River drainage. AUM 35629 (2, 45.3–50.9 mm SL),
Rupununi River 4.6 km NW Massara, 3.92603, -59.28037, 26-Oct-2002, J. Armbruster, M. Sabaj, D. Werneke, L
Allison, M. Thomas, C. Chin, D. Arjoon, M. James; AUM 35630 (1, 57.9 mm SL), Simoni River, 4 sites from 6.6
km SE to 3.2 km W Karanambo, 3.71917, -59.26121, 29-Oct-2002, J. Armbruster, M. Sabaj, L. Allison, M.
Thomas; AUM 37910 (2, 54.5–55.0 mm SL), Kuyuwini River at Parabara, just downstream of Kuyuwini Landing,
155 km SSE Lethem, 2.09585, -59.24116, 4-Nov-2003, J. Armbruster, M. Sabaj, M. Hardman, D. Arjoon, N.
Lujan, L. de Souza; AUM 38094 (2, 42.8–43.8 mm SL), Madkauwau Creek, tributary of Kuyuwini River between
Kuyuwini Landing and Parabara, 155 km SSE Lethem, 2.09672, -59.24346, 4-Nov-2003, J. Armbruster, M. Sabaj,
M. Hardman, D. Arjoon, N. Lujan, L. de Souza; AUM 38820 (2, 40.0–63.8 mm SL), Kuyuwini River at Kuyuwini
Landing, 2.09860, -59.24936, 14-Nov-2003, J. Armbruster, M. Sabaj, M. Hardman, D. Arjoon, N. Lujan, L. de
Souza; AUM 48162 (6, 64.0–87.8 mm SL), Burro Burro River at Surama, 4.18256, -59.06375, 23-Nov-2007, L. de
Souza, D. Taphorn, J. Baskin, T. Geerinckx, J. Hwan. Guyana, Berbice River Drainage: ROM 88561 (3, not
measured), Berbice River about 1 km downstream of Cat Creek. 4.96558, -58.24321, 27-Mar-2010, D. Bloom, D.
Taphorn, C. Bernard, H. López-Fernández, J. Maldonado, L. Wilson, R. Vandenburg.
Diagnosis. Ancistrus leucostictus differs from all other Ancistrus in the region except A. brevifilis (endemic to
the Tuy River Basin in Venezuela), A. saudades (from Amazon River tributaries in southern Guyana, and Guyana
Shield rivers of the Orinoco Basin in Venezuela), and A. triradiatus (from Orinoco River Basin in Venezuela) by
having light, large spots on the caudal fin, abdomen, dorsum of head and body and sides (these can be obscured in
preserved specimens, but spots generally remain on the fins, vs. body and fins all dark color with very small white
spots, spots may be absent in preserved specimens) in all other Ancistrus in the region. Ancistrus leucostictus can
be separated from A. saudades by having the adpressed dorsal fin reaching to at least the middle of the adipose-fin
spine (vs. to middle of preadipose plate), by having the pectoral-fin spine when adpressed ventral to the pelvic fin
reaching the base of the cloacal tube (vs. short of the cloacal papilla), and by having relatively larger light spots and
narrower dark interspaces on the anterolateral plates and posterodorsal head bones with the interspaces much less
than half the width of the spots and at least some spots always visible in this area on preserved specimens (vs.
interspaces half or greater the diameter of the spots and the spots often obscured in this region in preserved
specimens; the difference in spots vs. interspaces generally works on the abdomen as well); from A. brevifilis by
having round spots on the caudal fin (vs. oval spots), and from A. brevifilis and A. triradiatus by having spots on
the abdomen in life (vs. spots absent).
Description. Morphometrics given in Table 3. A large-sized Ancistrus, body broadest anteriorly, greatest body
width just posterior to opercles, then narrowing progressively to end of caudal peduncle. Head and body depressed,
greatest body depth between level of pectoral-fin insertions and dorsal-fin origin. Caudal peduncle deep, robust,
compressed posteriorly. Dorsal profile of head ascending steeply in convex arc from tip of snout to just posterior of
orbits, ascending in straight line to posterior tip of supraoccipital, then descending to dorsal-fin origin. From the
dorsal-fin origin descending in a slight convex arc to just posterior of dorsal-fin base, then straight to caudal fin.
Ventral profile flat to slightly convex from tip of snout to pelvic-fin insertions. Abdomen flat to slightly concave to
pelvic-fin insertions, from there, straight to slightly convex and sloping gently ventrally towards caudal fin.
Head wide, interorbital width equal or slightly less than head depth, slightly less than half of head length.
Snout rounded with large broad naked margin in males, less wide in females and juveniles. Snout length about one-
half head length. Eye moderate in size, interorbital area slightly convex. Oral disk ovate, wider than long. Lips
covered with minute papillae, larger near mouth. Lower lip moderate in size, not reaching gill aperture, its border
covered with very small papillae. Maxillary barbel very short, its length less than orbit diameter. Jaws moderate
with premaxillary tooth rows forming strong arc and dentary tooth rows forming angle of >135°. Dentary and
premaxillary tooth rows strongly curved medially, lateralmost dentary tooth medial to lateralmost premaxillary
tooth. Teeth numerous (36–62 per jaw ramus), asymmetrically bifid, medial cusp much larger and spatulate, lateral
cusp minute and pointed, usually not reaching more than half length of medial cusp, equal in worn teeth.
Hypertrophied cheek odontodes strongly evertible, eight to 17, stout with tips hooked anteriorly, bases encased in
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thick fleshy sheaths. Exposed part of opercle small, roughly triangular with larger odontodes along free edge. Head
smooth, bones on back of head not carinate; supraoccipital with margins between surrounding bones and plates
usually clearly visible. Lateral plates not carinate, lateral line pores distinctly visible, horizontally elongate.
TABLE 3. Morphometric features of Ancistrus leucostictus (N=15, except
1
N=12) and A. lithurgicus (N =22, except
2
N=20).
A. leucostictus A. lithurgicus
Feature Avg. SD Min Max Avg. SD Min Max
SL (mm) 54.1 10.3 102.8 63.8 17.6 35.5 100.3
% SL
Predorsal Length 46.8 1.6 44.4 48.8 46.0 1.6 43.3 49.0
Head Length 37.8 1.3 35.3 40.1 37.8 1.7 34.9 42.4
Head-dorsal Length 9.3 1.0 7.5 11.3 9.0 1.0 6.9 10.3
Cleithral Width 32.8 2.5 26.5 35.7 35.8 1.0 34.1 37.8
Head-pectoral Length 29.0 1.7 26.5 31.8 30.5 1.8 28.0 36.2
Thorax Length 24.9 1.2 23.2 27.1 24.4 1.3 21.8 26.5
Pectoral-spine Length 35.4 2.6 31.3 39.6 33.6 1.6 30.1 37.2
Abdominal Length 22.0 1.6 18.7 24.8 23.3 0.9 21.2 24.8
Pelvic-spine Length 25.9 1.2 23.7 27.6 26.6 1.0 24.5 28.0
Postanal Length 31.5 1.7 28.5 34.8 32.5 1.1 30.5 34.5
Anal-fin spine Length 9.5 1.4 6.9 11.8 9.6
2
1.0 7.1 11.3
Dorsal-pectoral Distance 29.1 1.3 26.8 31.4 27.8 1.1 25.7 29.6
Dorsal spine Length 30.1
1
1.3 28.4 32.9 29.6 1.7 26.3 32.8
Dorsal-pelvic Distance 20.7 2.8 13.9 24.9 19.5 1.1 16.6 21.8
Dorsal-fin base Length 25.8 2.4 21.8 29.8 25.8 1.6 22.1 28.0
Dorsal-adipose Distance 16.9 1.0 15.3 18.8 16.3 1.0 14.8 18.7
Adipose-spine Length 8.4 1.0 6.9 10.3 8.2 0.8 6.4 9.7
Adipose-up. caudal Distance 14.0 2.3 11.1 20.1 14.2 1.0 12.4 16.2
Caudal peduncle Depth 10.9 0.7 9.9 12.3 10.5 0.6 9.6 11.9
Adipose-low. caudal Distance 20.2 1.2 18.6 23.0 20.5 1.1 18.6 22.5
Adipose-anal Distance 19.6 1.3 16.5 21.3 19.8 1.1 18.1 21.9
Dorsal-anal Distance 14.2 1.1 12.4 15.7 13.1 0.8 11.7 14.7
Pelvic-dorsal Distance 23.3 3.5 14.8 27.3 23.9 1.7 20.6 27.4
% Head Length
Head-eye Length 40.8 2.1 36.5 46.2 38.1 2.6 34.0 44.4
Orbit Dia. 18.7 1.8 15.4 22.0 18.9 2.2 14.6 23.1
Snout Length 57.4 2.3 52.4 61.9 57.5 4.5 48.4 65.2
Internares Width 20.9 1.1 18.4 22.3 19.7 1.7 16.6 22.6
Interorbital Width 60.4 2.2 56.1 63.2 57.8 3.1 52.8 63.1
Head Depth 63.9 2.7 58.0 68.9 62.8 3.6 56.3 68.0
Mouth Length 47.6 1.5 44.7 49.9 50.9 3.7 42.1 58.4
Mouth Width 50.6 2.4 46.3 55.5 60.8 4.8 51.0 69.7
Barbel Length 5.1 1.7 3.0 8.2 6.6 2.3 3.7 12.8
Dentary tooth cup Length 13.9 1.1 11.6 15.4 17.2 1.6 13.5 19.7
Premaxillary tooth cup Length 15.0 1.4 11.1 16.8 17.5 1.9 13.0 21.1
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FIGURE 13. Ancistrus leucostictus in dorsal, lateral, and ventral views, AUM 48162, 185.3 mm SL. Scale = 1 cm. Photos by
J.W. Armbruster.
Ventral surface of head and abdomen naked, no exposed platelets anterior to anal-fin spine. Nuchal plate small
and curved posterolaterally. No enlarged odontodes at edge of lateral plates. Five series of lateral plates anteriorly,
three series on caudal peduncle, mid-dorsal and mid-ventral plate series end on caudal peduncle beneath adipose-
fin spine. Last plate in median series slightly smaller than penultimate plate, and median plate below end of adipose
fin about twice as high as wide. Base of caudal fin with six platelets covering bases of caudal-fin rays.
Dorsal-fin origin situated anterior to vertical through pelvic-fin insertion. First dorsal-fin ray not elongate, just
slightly longer than snout length; last dorsal-fin ray reaching first preadipose plate when depressed. Adipose-fin
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spine not embedded, oriented at an angle to horizontal axis of body, membrane present, easily visible beneath
spine. Pectoral spine long and stout, when adpressed ventrally it reaches to the cloaca, which we categorize as
maximum length (long). Anal fin small but well developed; base of first anal-fin pterygiophore covered by skin, its
origin below or posterior to vertical through base of last dorsal-fin ray. Pelvic fins reaching well past anal-fin
origin, inserted posterior to vertical through first branched dorsal-fin ray. Caudal fin truncate, lower lobe longer
than upper. Tiny odontodes present on body plates, largest on posterior margins of plates. All fin spines with small
odontodes, more developed in pectoral-fin spine of males. All fin rays with tiny odontodes on rays.
Meristics (N=15), mid-ventral plates 16–18, x̃ = 17; median plates 22–24, x̃ = 23; mid-dorsal plates 16–19, x̃ =
17; plates bordering dorsal-fin base seven to eight, x̃ = seven; plates between dorsal and adipose fins four to seven,
x̃ = five; preadipose plates one. Fin-ray formulae invariable (N=15): dorsal II,6–8, x̃ = II,7; pectoral I,6; pelvic i,5;
anal i,4; caudal i,14,i. Caudal procurrent spines: dorsal: three to five, x̃ = four; ventral: two to four, x̃ = three.
Sexual dimorphism. snout tentacles of nuptial males longer than in females, largest over twice eye diameter.
Posteromedial tentacles diverging in V-shape along anteriorly triangular snout plates. Naked areas of snout without
tentacles rugose, separated from naris by several wide plates; naked area wide, distance from anteromedial plate to
snout greater than or equal to distance from anteromedial plate to line formed between anterior edges of nasal
apertures.
Color in alcohol. (Fig. 13) Base color light brown with medium light spots concentrated on head and snout,
sometimes looking netlike, especially in juveniles. Plateless area of snout and tentacles also light brown with light
spots. All fins with alternating dark and light spots. Ventral surface of head and abdomen tan to yellowish tan, oral
disk yellowish, plates of ventral surface of caudal peduncle with posterior margins darker brown, forming
alternating light and dark pattern. Medium white spots on ventral surface of head and abdomen. Dark interspaces
on the head, anterior body, and abdomen usually less than half the width of the spots.
Life colors. Base color brown and gray with medium white irregularly-shaped spots concentrated on the head
and snout. Body posterior to dorsal-fin origin equally spotted. Preadipose plate and vestiges of adipose-fin spine
outlined in yellow. Sides with irregular light and dark spots. Ventrum of body with light brown base color and
medium irregularly-shaped white spots. Oral disk and adjacent area on chest pink to whitish. Fin membranes
lightly pigmented, grayish. Spines and rays brown in color with spots on all fins. Dark interspaces on the head,
anterior body, and abdomen usually less than half the width of the spots.
Distribution. Found throughout the middle and upper Essequibo River system of Guyana (Fig. 7). Probably
present in the Cuyuni River drainage in Venezuela.
Ancistrus lithurgicus Eigenmann 1912
(Figs. 14–15)
Ancistrus lithurgicus Eigenmann, 1912: 241, pl. 25 (fig. 3). Type locality: Crab Falls; Lower Essequibo, British Guiana.
Holotype: FMNH 53091 [approximately 5.403128, -58.820068].
Specimens examined. Guyana, Essequibo River Basin. ANSP 177368 (4, 55.5–66.8 mm SL), Burro Burro River,
Water Dog Falls camp, 4.68056, -58.83463, 20-Nov-1997, E. McBirney, W. Prince, D. Jaferally, et al.; ANSP
177369 (4, 49.9–70.5 mm SL), Burro Burro River, Water Dog Falls camp, 4.68056, -58.84833, 20-Nov-1997, E.
McBirney; AUM 37941 (1, 40.4 mm SL), Essequibo River at Kurukupari, 4.66149, -58.67519, 17-Nov-2003, M.
Sabaj, M. Hardman, N. Lujan, L. de Souza, D. Arjoon; AUM 38150 (1, 85.7 mm SL), Kuyuwini River 60.6 km
ENE Kuyuwini Landing, 179 km SE Lethem, 2.19313, -058.70407, 6-Nov-2003, J. Armbruster, M. Sabaj, M.
Hardman, D. Arjoon, N. Lujan, L.S. de Souza; AUM 38182 (1, 100.3 mm SL), Kuyuwini River 48.4 km E
Kuyuwini Landing, 182 km SE Lethem, 2.06496, -58.80917, 6-Nov-2003, J. Armbruster, M. Sabaj, M. Hardman,
D. Arjoon, N. Lujan, L.S. de Souza; AUM 38821 (5, 65.4–92.1 mm SL), 2.09860, -59.24936, Kuyuwini River at
Kuyuwini Landing, 14-Nov-2003, J. Armbruster, M. Sabaj, M. Hardman, D. Arjoon, N. Lujan, L.S. de Souza;
AUM 45300 (1, 49.6 mm SL), Essequibo River at Pisham-Pisham rapids, 4.43153, -58.48643, 4-Dec-2005, L. de
Souza, N. Lujan, D. Taphorn, J. Hartsell, E. Liverpool, S. Lord; FMNH 53091 (1, 68.5 mm SL) (holotype),
Essequibo River at Crab Falls, 5.39439, -58.86854, Sep-1908, C. Eigenmann; FMNH 53092 (3, 42.8–63.4 mm
SL) (paratypes), Essequibo River at Crab Falls, 5.39439, -58.86854, Sep-1908, C. Eigenmann; USNM 66104 (1,
35.5 mm SL) (paratype), Essequibo River at Crab Falls, 5.39439, -58.86854, Sep-1908, C. Eigenmann. Guyana,
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East Berbice, Berbice River Basin. ROM 86895 (14, SL unrecorded), Doreen Bank Creek, about 100-200m
upstream of mouth in fast to moderate flowing water, 4.93237, -58.22445, 26-Mar-2010, H. López-Fernández, C,
Bernard, J. Maldonado, L. Wilson, D. Bloom, D. Taphorn, F. Gonzales, R. Vandenburg, E. Holm; ROM 88561 (3,
SL unrecorded), Berbice River, about 1 km downstream of Cat Creek, 4.96558, -58.24321, 27-Mar-2010, D.
Bloom, D. Taphorn, C. Bernard, H. López-Fernández, J. Maldonado, L. Wilson, R. Vandenburg; ROM 88607 (1,
SL unrecorded), Berbice River, side channel (left side looking downstream) by island, 5.15107, -58.19616, 28-
Mar-2010, C. Bernard, J. Maldonado, E. Holm, H. López-Fernández.
Diagnosis. Ancistrus lithurgicus can be separated from all Ancistrus in the region except A. leoni and A.
macropthalmus by being very dorsoventrally flattened, having the eyes mostly dorsally placed (vs. mostly laterally
placed in other Ancistrus), and by having the median plate below the posterior edge of the adipose-fin membrane
just slightly taller than wide (vs. about twice as wide as tall). Ancistrus lithurgicus can be separated from A. leoni
by being black with white to golden dots and no dorsal saddles (vs. brown with white spots), by having the plates
along the median line on the snout forming a triangle (vs. a narrow column); from A. macrophthalmus by having
posteromedial tentacles forming a V-shape (vs. U-shape) and by having the pelvic fin reaching to nearly the end of
the anal fin when both fins are adpressed (vs. to just barely beyond base of pelvic fin); and from A. leoni and A.
macrophthalmus by having the eyes not as dorsally located with the medial section of the interorbital space most
elevated (vs. the orbital ridge higher than interorbital space). The dark color with small white to golden dots
sparsely present on the entire body and fins present in A. lithurgicus separates the species from all other potentially
sympatric Ancistrus except A. nudiceps (A. kellerae has small yellow spots present only on the head and nape and
A. leucostictus has large white spots on the body and fins).
Description. Morphometrics given in Table 3. A medium-sized Ancistrus, with a maximum size recorded of
100 mm SL. Body broadest anteriorly, greatest body width just posterior to opercles, then narrowing progressively
to end of caudal peduncle. Head and body depressed, greatest body depth between level of pectoral-fin insertions
and dorsal fin origin. Caudal peduncle deep, compressed posteriorly. Dorsal profile of head ascending steeply from
snout tip to nares, then ascending in gentle convex arc to dorsal-fin origin. From the dorsal-fin origin descending in
a straight line to posterior adipose-fin tip, then ascending slightly to caudal fin. Ventral profile flat, abdomen
slightly convex or concave depending on state of preservation or fullness of intestines.
Head wide, interorbital width equal or slightly less than head depth, less than half of head length. Snout
rounded with large broad naked margin in males, less wide in females and juveniles. Snout length more than one-
half head length. Eye large in size, interorbital area flat or slightly convex. Oral disk ovate, wider than long. Lips
covered with minute papillae, larger near mouth. Lower lip moderate in size, not reaching gill aperture, its border
covered with very small papillae. Maxillary barbel very short, its length less than orbit diameter. Jaws long with
premaxillary tooth rows forming gentle arc and dentaries forming angle of >135°. Dentary and premaxillary tooth
rows slightly curved medially, most lateral dentary tooth slightly medial to most lateral premaxillary tooth. Teeth
numerous (50–130 per jaw ramus), asymmetrically bifid, medial cusp much larger, longer and spatulate, smaller
lateral cusp pointed, equal in worn teeth. Hypertrophied cheek odontodes strongly evertible, eight to 16, stout with
tips hooked anteriorly, bases encased in thick fleshy sheaths. Exposed part of opercle small, roughly triangular,
covered with odontodes that are stouter near free edge.
Head smooth, bones on back of head not carinate; supraoccipital with margins between surrounding bones and
plates usually clearly visible. Lateral plates not carinate, lateral line pores not easily visible.
Ventral surface of head and abdomen naked, no exposed platelets anterior to anal-fin spine. Nuchal plate small
and curved posterolaterally. Odontodes at edge of lateral plates larger than rest. Five series of lateral plates
anteriorly, three series on caudal peduncle, mid-dorsal and mid-ventral plate series end on caudal peduncle beneath
adipose-fin spine. Last plate in median series same size as penultimate plate, and median plate below end of
adipose fin just slightly higher than wide. Base of caudal fin with about ten platelets covering bases of caudal-fin
rays.
Dorsal-fin origin situated anterior to vertical through pelvic-fin insertion. First dorsal-fin ray not elongate but
much longer than snout length; last dorsal-fin ray reaching first preadipose plate when depressed. Adipose-fin
spine not embedded, oriented at angle to horizontal axis of body, membrane present, easily visible beneath spine.
Pectoral spine moderate in length, when adpressed ventrally reaching beyond the pelvic-fin base, but not to the
cloaca. Anal fin small but well developed; base of first anal-fin pterygiophore covered by skin, anal-fin origin
posterior to vertical through base of last dorsal-fin ray. Pelvic fins reaching well past anal-fin origin, inserted
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FIGURE 14. Ancistrus lithurgicus in dorsal, lateral, and ventral views, AUM 38182, 100.3 mm SL. Scale = 1 cm. Photos by
J.W. Armbruster.
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FIGURE 15. Live coloration of Ancistrus lithurgicus in dorsal and dorsolateral views, AUM 37941, 40.4 mm SL. Scale = 1
cm. Photo by M.H. Sabaj.
posterior to vertical through first branched dorsal-fin ray. Caudal fin truncate, lower lobe longer than upper. Tiny
odontodes present on body plates, largest on posterior margins of plates. All fin spines with small odontodes, more
developed in pectoral-fin spine of males. All fin rays with tiny odontodes on rays.
Meristics (N=22). Mid-ventral plates 16–20, x̃ =18; median plates 21–23, x̃ = 22; mid-dorsal plates 16–20, x̃ =
18; plates bordering dorsal-fin base seven to eight, x̃ = eight; plates between dorsal and adipose fins four to seven,
x̃ = five; preadipose plates one. Fin-ray formulae invariable: dorsal II,7; pectoral I,6; pelvic i,5; anal i,4; caudal
i,14,i. Caudal procurrent spines: dorsal: three to five, x̃ = five; ventral: one to four, x̃ = three.
Sexual dimorphism. Snout tentacles of nuptial males short, largest approximately eye diameter.
Posteromedial tentacles diverging in broad V-shape along anteriorly triangular snout plates. Naked areas of snout
without tentacles rugose, separated from naris by one narrow plate; naked area narrow, distance from anteromedial
plate to snout less than distance from anteromedial plate to line formed between anterior edges of nasal apertures.
Color in alcohol. (Fig. 14) Base color of all fins, dorsum, sides and ventrum of body brown or gray with tiny
white dots; dots often lost in preservative. First dorsal-fin membrane dark black near its base. Lower caudal-fin
lobe darker than upper. Abdomen and oral disk lighter than rest of body.
Life colors. (Fig. 15) Black; a few minute white dots on back and fins, more numerous on belly, sometimes
quite obscure; all fins black, the dorsal and caudal margined with white sor yellow (Eigenmann, 1912).
Distribution: Ancistrus lithurgicus is found in the Essequibo and Berbice River Basins in Guyana (Fig. 7).
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Ancistrus macrophthalmus Pellegrin (1912)
(Figs. 16–17)
Xenocara macrophthalma Pellegrin, 1912: 271, fig. 1. Type locality: l’Orénoque [Venezuela]. Holotype: MNHN 1887-0650.
Specimens examined. Colombia: IAvHP 7001 (1, 62.6 mm SL), Departament of Vichada, Cumaripo
Municipality, Tomo River, 5.379390, -68.059257, 2-May-2004. Venezuela: Amazonas state: ANSP 162171 (1,
70.1 mm SL), Ventuari River ca 12 km from its confluence with the Orinoco, backwater and rocky pools,
4.058312, -66.932861, 25-Mar-1987, B. Chernoff, W. Saul, J. Fernandez, M. Antonio, M. Gutierrez; ANSP
162402 (2, 54.1–54.5 mm SL) Orinoco River backwater behind sand beach, 1/2 hour upstream from Isla
Temblador, 3.089606, -66.443982, 10-Mar-1987, B. Chernoff, W. Saul, H. Lopez, J. Fernandez, O. Castillo, M.
Antonio, J. Moreno; ANSP 185312 (1, 76.8 mm SL), Orinoco River at Pasaganado, 38 km N San Fernando de
Atabapo, 4.399609, -67.776152, 1-Mar-2005, M.H. Sabaj, N. Lujan, D. Werneke, et al.; ANSP 185327 (2, 79.3–
79.3 mm SL), Ventuari River ca 20 air miles ENE of confluence w Orinoco, 4.07556, -66.89278, 3-Apr-2005, N.
Lujan, M. Arce, et al.; AUM 42096 (1, 60.6 mm SL), Orinoco River, beach and bedrock outcropping 50 km E of
San Fernando de Atabapo, 3.97029, -067.25506, 2-Mar-2005, N. Lujan, D. Werneke, M. Sabaj, M. Arce, R.
Betancur, T. Wesley; AUM 42105 (3, 67.3–77.2 mm SL), Orinoco River 50 km E of San Fernando de Atabapo;
3.96731 -067.25347, 3-Mar-2005, N. Lujan, D. Werneke, M. Sabaj, M. Arce; AUM 42133 (2, 76.7–80.6 mm SL),
Orinoco River at Pasaganado, 38 km N of San Fernando de Atabapo, 4.399609, -67.776152, 1-Mar-2005, N.
Lujan, D. Werneke, M. Sabaj, M. Arce, T. Wesley; AUM 42203 (6, 64.1–88.9 mm SL), Ventuari River, near
ornamental fish market on the river, 4.07565, -66.89285, 3-Apr-2005, N. Lujan, M. Arce, T. Wesley, et al.; AUM
42217 (1, 74.0 mm SL), Orinoco River near Puerto Ayacucho on a beach called Playa Bagre, 5.65642, -67.63103,
13-Apr-2005, N. Lujan, M. Arce, T. Wesley; AUM 43264 (1, 67.8 mm SL), Orinoco River 147 ESE of San
Fernando de Atabapo, 3.30662, -66.60342, 4-Mar-2005, N. Lujan, M. Sabaj, M. Arce, T. Wesley; FMNH 101046
(3, 52.7–91.0 mm SL), Orinoco River at Cupaven, rocks and rapids, 4.01180, -67.65121, 29-Jan-1991, A.
Machado-Allison, B. Chernoff, D. Machado-Aranda, J. Wheeler; MCNG 12361 (1, 58.3 mm SL), Negro River
district, Casiquiare River, Raudal Cabarua, approximately 5 Km. al N. of the confluencia of Siapa River, 2.11667, -
66.46667, 18-Apr-1985. Venezuela, Apure state: FMNH 69930 (1, 76.0 mm SL), lower Cinaruco River at
confluence of Madre Vieja, about 60 miles south of San Fernando de Apure, 6.55142, -67.50643, Feb-1967, W.
Braker et al.
Diagnosis. Ancistrus macrophthalmus differs from all other Ancistrus from the study region except A. leoni by
having the raised medial orbital ridges the most elevated point on the head (vs. the medial interorbital space highest
point on head), by the tentacles forming a wide U-shape on the central portion of the snout with lines of the
tentacles running from the snout tip to the eye margin (vs. running in a transverse line along the middle of the snout
or in a V-shape in most Ancistrus, a very narrow V in A. lithurgicus, or almost parallel in A. patronus), by having
the eyes almost completely dorsally placed (vs. almost lateral in all except A. leoni, which has the eyes in the same
position and A. lithurgicus where the eyes are about midway between the condition of most Ancistrus and A.
macrophthalmus); and from all Ancistrus except A. leoni and A. lithurgicus by having the median plate below the
end of the adipose-fin membrane being just slightly taller than wide (vs. being almost twice as tall as wide).
Outside of the region, Ancistrus macrophthalmus is most similar to the Brazilian A. ranunculus, which shares a
wide head and widely diverging rows of median snout tentacles; however, the diverging rows of tentacles in A.
ranunculus are much closer to the end of the snout (only slightly separated from the margin row of tentacles), and
the naked area of the snout does not reach the eyes (vs. reaching the eyes in A. macrophthalmus). Additionally, A.
macrophthalmus can be separated from A. ranunculus by being narrower, having the median plate below the
posterior edge of the adipose-fin membrane just slightly taller than wide (vs. about twice as tall as wide), and
having the pectoral-fin spine nearly reaching the cloaca when adpressed ventral to the pelvic fin (vs. reaching just
slightly beyond base of pelvic fin).
Description. Morphometrics given in Table 4. Size range of specimens examined 52.7–90.9 mm SL. A large
sized Ancistrus, body broadest anteriorly, greatest body width just posterior to opercles, then narrowing
progressively to end of caudal peduncle. Head and body extremely depressed, greatest body depth between level of
pectoral-fin insertions and dorsal-fin origin. Caudal peduncle deep, robust, compressed posteriorly. Dorsal profile
of head ascending slightly in convex arc from tip of snout to just posterior of orbits, ascending in straight line to
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posterior tip of supraoccipital, then descending to dorsal-fin origin. From the dorsal-fin origin compressed to the
posterior of dorsal-fin base, then straight to caudal fin. Ventral profile flat from tip of snout to pelvic-fin insertions.
Abdomen flat to slightly concave to pelvic-fin insertions, from there, straight, flat and sloping gently ventrally
towards caudal fin.
TABLE 4. Morphometric features of Ancistrus macropthalmus (N=25, except
1
N=22 and
2
N=25) and A. maracasae (N
=19, except
3
N=18).
A. macropthalmus A. maracasae
Feature Avg. SD Min Max Avg. SD Min Max
SL (mm) 71.5 10.5 52.7 91.0 72.0 12.6 38.6 96.8
% SL
Predorsal Length 45.6 2.0 42.1 50.3 46.9 1.4 44.6 49.3
Head Length 37.7 1.5 35.4 41.7 38.0 1.5 35.4 40.7
Head-dorsal Length 8.3 1.1 6.1 10.3 9.8 1.3 8.3 12.4
Cleithral Width 38.2 2.5 31.7 42.3 33.0 0.7 31.4 34.0
Head-pectoral Length 31.8 2.1 28.7 37.8 28.7 1.3 27.1 31.7
Thorax Length 23.7 2.1 19.6 28.5 23.7 1.3 20.6 25.6
Pectoral-spine Length 31.8 1.5 29.4 34.8 32.5 1.4 29.4 34.6
Abdominal Length 24.1 2.0 21.4 32.4 22.6 2.1 20.5 30.6
Pelvic-spine Length 25.5 1.6 22.1 29.0 24.3 2.6 20.8 33.9
Postanal Length 32.2 1.7 29.0 35.3 30.7 0.8 28.9 32.0
Anal-fin spine Length 10.1 2.6 0.0 13.9 10.6 1.0 9.2 12.5
Dorsal-pectoral Distance 27.7 1.3 25.3 29.9 28.8 1.5 24.2 31.4
Dorsal spine Length 27.8
1
2.0 23.8 30.3 27.1
3
2.4 23.9 30.9
Dorsal-pelvic Distance 19.9 2.0 16.5 24.4 22.0 2.1 19.6 29.0
Dorsal-fin base Length 25.5 1.8 21.6 28.6 24.9 1.2 22.6 27.1
Dorsal-adipose Distance 16.6 1.8 14.4 22.3 16.0 1.1 14.2 18.8
Adipose-spine Length 8.2
2
1.0 6.5 10.8 7.8 0.8 6.5 9.2
Adipose-up. caudal Distance 13.3 1.2 10.6 15.5 14.9 1.8 12.9 20.7
Caudal peduncle Depth 9.6 1.0 7.6 11.1 10.9 0.8 8.9 12.0
Adipose-low. caudal Distance 19.8 1.3 15.7 21.8 21.2 1.2 19.4 23.5
Adipose-anal Distance 18.2 1.1 16.4 21.1 19.7 0.6 18.5 20.7
Dorsal-anal Distance 11.8 1.1 10.3 14.6 15.0 0.5 13.6 15.7
Pelvic-dorsal Distance 24.8 1.8 22.0 29.1 25.1 1.2 23.0 26.9
% Head Length
Head-eye Length 38.4 1.8 34.7 41.4 40.4 1.9 35.5 43.8
Orbit Dia. 19.5 1.7 16.4 22.2 16.8 1.1 14.9 19.6
Snout Length 58.3 2.6 53.4 62.8 58.1 2.0 54.4 62.9
Internares Width 17.3 1.4 14.7 20.4 18.4 1.6 15.8 22.0
Interorbital Width 56.5 2.6 50.9 61.8 59.2 3.2 52.4 65.0
Head Depth 63.7 2.4 59.6 68.1 63.4 2.9 55.8 67.9
Mouth Length 50.3 4.5 41.6 60.4 46.1 3.0 40.5 50.9
Mouth Width 60.5 5.0 45.6 71.6 51.5 3.4 44.3 55.2
Barbel Length 7.8 2.6 3.3 12.5 5.6 1.4 3.0 7.6
Dentary tooth cup Length 15.6 1.4 12.8 19.0 16.8 1.6 13.3 19.5
Premaxillary tooth cup Length 16.3 1.5 11.7 18.3 17.4 1.7 12.9 19.6
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FIGURE 16. Ancistrus macropthalmus in dorsal, lateral, and ventral views, AUM 53526, 87.3 mm SL. Scale = 1 cm. Photos
by J.W. Armbruster.
Head wide, interorbital width equal or slightly less than head depth, slightly less than half of head length.
Snout rounded with large broad naked margin in males, less wide in females and juveniles. Snout length about one-
half head length. Eye large in size, interorbital area flat. Oral disk ovate, wider than long. Lips covered with minute
papillae, larger near mouth. Lower lip moderate in size, not reaching gill aperture, its border covered with very
small papillae. Maxillary barbel very short, its length less than orbit diameter. Jaws long with premaxillary and
dentary tooth rows forming almost straight lines (slightly <180°). Dentary and premaxillary tooth rows slightly
curved medially, lateralmost dentary tooth medial to lateralmost premaxillary tooth. Teeth numerous (45–104 per
jaw ramus), asymmetrically bifid, medial cusp much larger and spatulate, lateral cusp minute and pointed, usually
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not reaching more than half length of medial cusp, equal in worn teeth. Hypertrophied cheek odontodes strongly
evertible, eight to 15, stout with tips hooked anteriorly, bases encased in thick fleshy sheaths. Exposed part of
opercle small, roughly triangular with few odontodes. Head smooth, bones on back of head not carinate;
supraoccipital with margins between surrounding bones and plates usually clearly visible. Lateral plates not
carinate, lateral line pores distinctly visible, horizontally elongate.
Ventral surface of head and abdomen naked, no exposed platelets anterior to anal-fin spine. Nuchal plate small
and curved posterolaterally. No enlarged odontodes at edge of lateral plates. Five series of lateral plates anteriorly,
three series on caudal peduncle, mid-dorsal and mid-ventral plate series ending on caudal peduncle beneath
preadipose plate just anterior to embedded adipose-fin spine. Last plate in median series slightly smaller than
penultimate plate, and median plate below end of adipose fin just slightly higher than wide. Base of caudal fin with
six platelets covering bases of caudal-fin rays.
Dorsal-fin origin situated anterior to vertical through pelvic-fin insertion. First dorsal-fin ray elongate, just
slightly longer than snout length; last dorsal-fin ray reaching first preadipose plate when depressed. Adipose-fin
spine (if present) embedded, oriented parallel to horizontal axis of body, membrane present, visible beneath spine.
Pectoral spine short and stout, when adpressed ventrally reaching to slightly posterior to insertion of the pelvic fin,
which we categorize as medium distance (medium). Anal fin small but well developed; base of first anal-fin
pterygiophore covered by skin, its origin below or posterior to vertical through base of last dorsal-fin ray. Pelvic
fins reaching past anal-fin origin, inserted posterior to vertical through first branched dorsal-fin ray. Caudal fin
truncate, lower lobe slightly longer than upper.
Tiny odontodes present on body plates, largest on posterior margins of plates. All fin spines with small
odontodes, more developed in pectoral-fin spine of males. All fin rays with tiny odontodes on rays.
Meristics (N=26). Mid-ventral plates 15–17, x̃ = 17; median plates 21–24, x̃ = 22; mid-dorsal plates 16–19, x̃ =
18; plates bordering dorsal-fin base six to eight, x̃ = seven; plates between dorsal and adipose fins three to seven, x̃
= five; preadipose plates one. Fin-ray formulae: dorsal II,7; pectoral I,6; pelvic i,5; anal i,3–4, x̃ i,4; caudal i,14,i.
Caudal procurrent spines: dorsal three to five, x̃ = four; ventral: one to three, x̃ = two.
Sexual dimorphism. Snout tentacles of nuptial males long, largest approximately 1.5 times eye diameter.
Posteromedial tentacles diverging in a broad U-shape along anteriorly triangular snout plates. Naked areas of snout
without tentacles rugose, separated from naris by several, wide plates; naked area narrow, distance from
anteromedial plate to snout less than distance from anteromedial plate to line formed between anterior edges of
nasal apertures.
FIGURE 17. Live coloration of Ancistrus macropthalmus in dorsal and lateral views, AUM 43264, 67.8 mm SL. Scale = 1 cm.
Photo by M.H. Sabaj.
Color in alcohol. (Fig. 16) Dorsum of body base color dark brown with well-separated small white dots on the
plateless area of snout, head and body. Opercle and sides of head, body and caudal peduncle also dark brown with
white dots as on dorsum. Spines and rays of fins dark brown, membranes translucent clear or light gray. Oral disk
and ventral surfaces of head and abdomen yellowish, lower lip in some smaller specimens with narrow gray edges.
Ventrum of caudal peduncle lighter than sides, with small white dots. Some specimens with pigment pattern mostly
faded to varying degrees of brown, with light dots not visible.
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Life colors. (Fig. 17) Dorsum dark gray, small cream to yellowish dots on plateless area of snout, top of head,
tentacles and entire length of body. Dots on head more numerous, smaller and closer together on top of head than
on dorsum of body. Sides of head of body dark gray with white dots to caudal fin. Ventrum of head and body white.
Oral disk and adjacent area on chest light. Spines, rays and fin membranes gray with white dots. Caudal-fin spine,
rays and fin membrane light gray with no dots.
Distribution. Found in the upper Orinoco River system from the río Cinaruco and further upstream to the río
Casiquiare (Fig. 7).
Ancistrus nudiceps (Müller & Troschel 1849)
(Figs. 1 and 18)
Hypostomus nudiceps Müller & Troschel, 1848: 631. Type locality: dem Takutu, Britisch-Guiana. Holotype: ZMB 3180.
Specimens examined. Guyana, Amazon River Basin: ANSP 185301 (1, 120.0 mm SL), Takutu River ca 2.75 km
W of Saint Ignatius 3.35500, -21.30093, 5-Nov-2002, M. Sabaj, J. Armbruster, M. Thomas, D. Werneke, C.
Allison, C. Chin, D. Arjoon, L. Atkinson; AUM 35628 (2, 93.8-113.5 mm SL), Takutu River ca.2.75 km W Saint
Ignatius, 3.35500, -59.83077, 5-Nov-02, J.W. Armbruster, M.H. Sabaj, D.C. Werneke, C.L. Allison, M.R. Thomas,
C.J. Chin, D. Arjoon, Atkinson; AUM 44666 (1, 118.2 mm SL), Pirara River, at Pirara Ranch, 3.62517, -59.67688,
26-Nov-2005, L.S. de Souza, N.K. Lujan, D.C. Taphorn, J.A. Hartsell, E. Liverpool, S. Lord; AUM 44701 (5,
55.8-126.0 mm SL), Takutu River, near Lethem, 3.47043, -59.80993 27-Nov-2005, L.S. de Souza, N.K. Lujan,
D.C. Taphorn, J.A. Hartsell, E. Liverpool, S. Lord; AUM 47720 (2, 74.2-91.1 mm SL), Takutu River, rock beach;
3.47058, -59.80990 11-Nov-2007, L.S. de Souza, D.C. Taphorn, J.N. Baskin, T. Geerinckx, J.L. Hwan; AUM
47793 (4, SL unrecorded) Takutu River, Garlic landing, beach N of Lethem, 3.42147, -59.81253, 17-Nov-2007,
L.S. de Souza, D.C. Taphorn, J.N. Baskin, T. Geerinckx, J.L. Hwan; AUM 48095 (1, 81.8 mm SL), Takutu River,
N of Sand Creek; 2.95817, -59.95913 15-Nov-2007, L.S. de Souza, D.C. Taphorn, J.N. Baskin, T. Geerinckx, J.L.
Hwan; AUM 50795 (not measured), Takutu River, Tom’s beach, 3.41058, -59.81935, 11-Nov-200, L.S. de Souza,
D.C. Taphorn, J.N. Baskin, T. Geerinckx, J.L. Hwan. Guyana, Essequibo River Basin: ANSP 175917 (2, 54.5-55.3
mm SL), Stream effluent from Turtle Pond, 4.75417, -58.75333, 26-Jan-1997, W. Saul, N. Liley, G. Watkins, D.
Torres, D. Allicock, E. McBirney, C. Watson; ANSP 177307 (1, 103.7 mm SL), Potaro/Siparuni River drainage,
Pakatnu Falls Creek; 4.74972, -59.02694, 6-Dec-1997, W. Saul, N. Liley, G. Watkins, D. Torres, D. Allicock, E.
McBirney, C. Watson; ANSP 39739 (1, 86.8 mm SL), Rupununi River, 3.29488, -59.34911 1911–1912, J. Ogilvie;
AUM 35625 (3, 66.1-89.5 mm SL), Rupununi River 3.7 km SSE Massara, 3.86228, -59.28439 27-Oct-2002, J.W.
Armbruster, M.H. Sabaj, D.C. Werneke, C.L. Allison, M.R. Thomas, C.J. Chin, D. Arjoon, S. Mario ; AUM 35627
(not measured) Stream 10.3 km NW Karanambo, 3.80758, -59.38490 28-Oct-2002, J.W. Armbruster, M.H. Sabaj,
D.C. Werneke, C.L. Allison, M.R. Thomas, C.J. Chin, D. Arjoon, M James; AUM 35623 (2), 81.8-138.4 mm SL),
Rupununi River 4.6 km NW Massara, 3.92603, -59.28037, 26-Oct-2002, J.W. Armbruster, M.H. Sabaj, D.C.
Werneke, C.L. Allison, M.R. Thomas, C.J. Chin, D. Arjoon, M James; AUM 38929 (not measured), backwater and
mainstem of Kuyuwini River 19.5 km W of Kuyuwini River mouth, 2.24098, -58.50093, 11-Nov-2003, J.W.
Armbruster, M.H. Sabaj, M. Hardman, D. Arjoon, N.K. Lujan, L.S. de Souza; AUM 44511 (10, 48.0-81.7 mm SL),
Bununi Creek, 9.8 miles W of Massara, on the way to Toka, 3.86947, -59.43380, 25-Nov-2005, L.S. de Souza,
N.K. Lujan, D.C. Taphorn, J.A. Hartsell, E. Liverpool, S. Lord; AUM 45092 (1, 51.0 mm SL), Pond at Surama,
4.14845, -59.04015, 3-Dec-2005, L.S. de Souza, N.K. Lujan, D.C. Taphorn, J.A. Hartsell, E. Liverpool, S. Lord;
AUM 47882 (2, 90.1-97.0mm Rupununi River at Kwatamang landing; 03.91798, -059.10053, 5-Nov-2007, L.S. de
Souza, D.C. Taphorn, J.N. Baskin, T. Geerinckx, J.L. Hwan; AUM 48397 Bununi Creek, 0.5 miles S of Massara,
3.87080, -59.31630, 7-Nov-2007, L.S. de Souza, D.C. Taphorn, J.N. Baskin, T. Geerinckx, J.L. Hwan; AUM
49800 (1, 102.0 mm SL), Rupununi River at Massara Landing, 3.89500, -59.29370 6-Nov-2007, L.S. de Souza,
D.C. Taphorn, J.N. Baskin, T. Geerinckx, J.L. Hwan; AUM 50295 (not measured), Rupununi River at Kwaimatta
landing, 3.84112, -59.30450, 7-Nov-2007, L.S. de Souza, D.C. Taphorn, J.N. Baskin, T. Geerinckx, J.L. Hwan;
FMNH 53086 (1, 42.3 mm SL), Essequibo River at Gluck Island, 5.98303, -58.58174, 1908, C. Eigenmann;
FMNH 53093 (1, 44.0 mm SL), Essequibo River at Gluck Island, 5.98303, -58.58174 1908, C. Eigenmann;
FMNH 53144 (3, 53.5-83.9 mm SL), Essequibo/Rupununi Pan, 1908, C. Eigenmann; FMNH 53556 (1, 74.0 mm
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SL), Essequibo River at Packeoo Falls, 6.03715, -58.58438 1908, C. Eigenmann; FMNH 7412 (1, 74.0 mm SL),
Rupununi Pan opposite Massara Landing, 3.89584, -59.29296 1908, C. Eigenmann; INHS 49273 (1, 100.3 mm
SL), Essequibo River (Long Lake, 1.54 miles S of Rockstone, 5.96686, -58.56322, 20-Oct-1998, M. Sabaj, J.
Armbruster, M. Hardman, J. Knouft, W. Prince, I. Peterson; USNM 372570 (2, 46.6-52.8, Rupununi River,
Taraqua Creek, 3.75949, -59.28371, 31-Oct-2001, D. Arjoon. Venezuela, Bolivar state, Essequibo River Basin,
Cuyuni River drainage: ANSP 168173 (1, 85.2 mm SL), Rio Macaruma on Guasipati-El Miamo Rd, ca 4 km SW
of El Miamo, 7.44394, -61.87115, 24-Jan-1991, S. Schaefer, W. Saul, F. Provenzano; ANSP 168175 (2, 75.3-79.0
mm SL), Rio Corumo, 10 km E of Tumeremo on road from Tumeremo to Bochinche (just after Fort Terembay),
7.33053, -61.43732, 21-Jan-1991, S. Schaefer, W. Saul, F. Provenzano; ANSP 168176 (1, 49.3 mm SL), Caño
Curumito, tributary of Botanamo River, 7.42381, -61.23843, 22-Jan-1991, S. Schaefer, W. Saul, F. Provenzano;
AUM 36609 (3, 49.9-67.4, Río Macaruma, 134 km SE.of Cuidad Guiana, 5 km SE. of Guasipati, at old bridge just
W of the main road, 7.43773, -61.87554, 11-Jun-2003, J.W. Armbruster, D.C. Werneke, T.P. Pera, N.K. Lujan, O
León; INHS 31566 (1, 58.2 mm SL), Rio Oronata, S of town of Upata, (Rio Yuruari drainage), 7.54660, -62.24342,
9-Jan-1994, D.Taphorn, L. Page, K. Cummings, C. Mayer, J. Armbruster, C. Laird, M. Sabaj, C. Johnston, S.
Phelps, G. Mottesi; INHS 31582 (1, 77.4 mm SL), Rio Oronata, between Upata & El Manteco, (Rio Yuruari
drainage, 7.54660, -62.24342, 9-Jan-1994, D.Taphorn, L. Page, K. Cummings, C. Mayer, J. Armbruster, C. Laird,
M. Sabaj, C. Johnston, S. Phelps, G. Mottesi; INHS 31732 (1, 55.0 mm SL), Essequibo/Cuyuni/ Rio Guanare
(Yuruari River drainage, El Miamo, 7.64139, -61.77750, 11-Jan-1994, D.Taphorn, L. Page, K. Cummings, C.
Mayer, J. Armbruster, C. Laird, M. Sabaj, C. Johnston, S. Phelps, G. Mottesi; MCNG 1068 (1, 82.7 mm SL), Creek
of Botanamo River, 2.5 Km upstream of the confluence of Botanamo and Cuyuni Rivers, Bolivar state, 6.96667, -
61.20000, 28-Aug-1979, D. Taphorn, E. Salas; MCNG 10488 (1, 77.2 mm SL), Botanamo River, just downstream
of the mouth of the Gurampin in the forest, Bolivar state, 7.08611, -60.97222, 15-Jul-1983, B. Stergios, G. Aymard;
MCNG 16040 65.0 mm SL), Corumo River, at the bridge on highway Bochinche, 7.316667, -61.4, 21-Feb-1980,
D. Taphorn, G. Feo, G. Ríos.
Diagnosis. Ancistrus nudiceps differs from all other Ancistrus in the region except A. patronus, A. leoni, A.
lithurgicus, A. macrophthalmus and A. maximus by having an entirely black body with tiny white to golden dots; it
differs from A. maximus by usually having II,7 dorsal-fin rays (vs. II,8; two specimens of A. nudiceps are also II,8)
and by having smaller dots with no change in dot size with SL (vs. considerably larger spots in juveniles); from A.
patronus by reaching a much greater maximum size (138 mm SL vs. 86 mm SL), by having the plated region of the
snout forming a long, rounded triangle such that the area between the plates and the tip of the snout is much smaller
than the distance between the tip of the plated area and a line drawn between the anterior margins of the orbits (vs.
plated areas forming a broad arc and the distance from the plates to the tip of snout equal to the distance from the
tip of the plates to a line drawn between the anterior margin of the orbits), and by having the tentacles of the snout
bifurcating at the start of the snout plates in a V (vs. tentacles bifurcating in a U); and from A. leoni, A. lithurgicus,
and A. macrophthalmus by being deep bodied (vs. flattened), by having the median plate below the posterior edge
of the adipose-fin membrane about twice as tall as wide (vs. just slightly taller than), and by the eyes being laterally
placed (vs. dorsolaterally placed in A. lithurgicus and almost completely dorsally placed in A. leoni and A.
macrophthalmus.
Description. Morphometrics given in Table 5. Size range of specimens examined 42–138 mm SL. A relatively
large Ancistrus, body broadest anteriorly, greatest body width near opercles, then narrowing progressively to end of
caudal peduncle. Head and body somewhat depressed, greatest body depth just anterior to dorsal-fin origin. Caudal
peduncle deep, robust, compressed posteriorly. Dorsal profile of head and body ascending at about a 45 degree
angle to above eyes, then ascending gently in convex arc to dorsal-fin origin, from there, descending in straight line
or gently convex arc sloping gradually down to beneath adipose-fin, then angled dorsally to caudal fin. Ventral
profile flat to beneath pectoral-fin insertions, then slightly convex to pelvic-fin insertions, then descending straight
to caudal-fin spine.
Head wide, interorbital width greater than head depth, much more than half of head length. Snout rounded with
large broad naked margin in males, less wide in females and juveniles. Snout length more than one-half head
length. Eye large, interorbital area slightly convex. Oral disk round, about as wide as long. Lips covered with
minute papillae, larger near mouth. Lower lip moderate in size, not reaching gill aperture, its border covered with
very small papillae. Maxillary barbel very short, its length less than orbit diameter. Jaws short with premaxillary
tooth rows forming strong arc and dentary tooth rows forming angle of >135°. Dentary and premaxillary tooth
rows strongly curved medially, lateralmost dentary tooth medial to lateralmost premaxillary tooth. Teeth numerous
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ANCISTRUS NORTHWESTERN GUIANA SHIELD ORINOCO ANDES
(44–62 per jaw ramus), asymmetrically bifid, medial cusp much larger and spatulate, lateral cusp minute and
pointed, usually not reaching more than half length of medial cusp, but equal in worn teeth. Hypertrophied cheek
odontodes strongly evertible, eight –13, stout with tips hooked anteriorly, bases encased in thick fleshy sheaths.
Exposed part of opercle roughly an elongate diamond with rounded tips, covered with odontodes that are larger
along its margins. Head smooth, bones on back of head not carinate; supraoccipital with margins between
surrounding bones and plates usually clearly visible. Lateral plates not carinate.
FIGURE 18. Ancistrus nudiceps in dorsal, lateral, and ventral views, AUM 35623, 140.2 mm SL. Scale = 1 cm. Photos by J.W.
Armbruster.
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TABLE 5 . Morphometric features of Ancistrus nudiceps (N =60, except
1
N=51) and A. patronus n. sp. (N=47, except
2
N=44 and
3
N=46).
Ventral surface of head and abdomen naked, one exposed platelet present (tip of first pterygiophore) anterior to
anal-fin spine. Nuchal plate small and curved posterolaterally. Enlarged odontodes present along edges of lateral
plates. Five series of lateral plates anteriorly, three series on caudal peduncle, mid-dorsal plate series ending on
caudal peduncle beneath first preadipose plate; mid-ventral plate series ending on caudal peduncle beneath
A. nudiceps A. patronus n. sp.
Feature Avg. SD Min Max Avg. SD Min Max
SL (mm) 75.2 22.7 42.3 138.4 68.2 10.9 42.5 87.8
% SL
Predorsal Length 47.3 1.5 44.6 50.7 48.5 1.5 45.4 51.0
Head Length 39.2 1.8 35.8 44.5 39.1 1.2 36.6 42.5
Head-dorsal Length 8.6 1.0 6.2 11.3 9.6 1.1 7.0 12.1
Cleithral Width 33.9 2.4 27.7 38.4 31.4 2.2 26.9 34.9
Head-pectoral Length 30.9 2.0 25.7 34.9 29.9 1.3 27.3 33.0
Thorax Length 25.4 1.9 22.0 30.4 24.5 1.3 21.6 28.7
Pectoral-spine Length 33.2 4.8 0.0 38.0 32.8 1.5 28.9 35.5
Abdominal Length 22.3 1.7 20.3 32.6 22.7 1.1 20.0 25.1
Pelvic-spine Length 26.2 1.3 21.4 29.2 26.2 1.0 24.4 28.6
Postanal Length 30.6 1.3 27.0 33.2 29.6 1.8 23.5 36.6
Anal-fin spine Length 10.3 2.3 0.0 13.5 9.3 1.1 7.2 12.6
Dorsal-pectoral Distance 29.2 1.1 26.9 32.3 29.7 1.1 27.7 32.6
Dorsal spine Length 30.6 2.4 24.4 35.6 27.9
2
1.9 23.4 30.9
Dorsal-pelvic Distance 21.8 2.5 16.0 27.3 21.1 2.3 16.1 25.8
Dorsal-fin base Length 26.0 2.3 21.8 33.5 23.4 1.6 19.9 27.1
Dorsal-adipose Distance 17.1 1.4 13.4 20.7 17.0 1.3 14.5 20.2
Adipose-spine Length 7.9
1
1.0 5.8 10.7 8.5
3
1.1 6.1 11.0
Adipose-up. caudal Distance 12.3 1.5 8.3 15.5 12.7 1.5 8.4 16.9
Caudal peduncle Depth 10.5 0.9 8.4 12.8 10.7 0.8 8.7 12.3
Adipose-low. caudal Distance 18.9 0.8 17.2 20.6 19.3 1.4 15.4 22.4
Adipose-anal Distance 19.7 1.4 16.3 22.5 18.9 1.0 16.7 21.5
Dorsal-anal Distance 14.3 1.0 12.0 16.4 15.3 0.8 13.7 16.8
Pelvic-dorsal Distance 23.7 2.0 19.6 27.9 23.8 2.2 17.8 28.4
% Head Length
Head-eye Length 42.2 2.2 36.2 46.8 40.3 2.4 35.8 46.5
Orbit Dia. 17.7 1.7 13.3 21.6 19.3 1.8 16.2 23.7
Snout Length 57.5 2.6 50.8 63.8 59.8 1.9 55.6 65.4
Internares Width 23.2 2.3 17.2 28.9 20.4 1.4 16.2 22.8
Interorbital Width 59.8 2.9 52.6 68.0 58.1 2.5 52.2 63.3
Head Depth 63.6 3.4 48.1 69.0 63.1 2.2 58.0 67.4
Mouth Length 47.9 3.3 38.6 56.1 49.2 2.8 43.0 55.7
Mouth Width 50.6 4.3 39.5 60.9 51.6 3.7 43.7 60.7
Barbel Length 5.8 1.8 2.0 10.7 6.0 1.5 1.7 9.5
Dentary tooth cup Length 14.4 1.7 11.4 20.0 13.2 1.4 10.5 16.2
Premaxillary tooth cup Length 14.7 1.7 11.9 21.0 13.5 1.8 10.1 17.6
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ANCISTRUS NORTHWESTERN GUIANA SHIELD ORINOCO ANDES
adipose-fin spine. Last plate in median series slightly same size as penultimate plate, and median plate below end
of adipose fin about twice as high as wide. Base of caudal fin with eight to 13 small platelets covering bases of
caudal-fin rays.
Dorsal-fin origin situated notably anterior to vertical through pelvic-fin insertion. First dorsal-fin ray not
elongate, longer than snout length; last dorsal-fin ray reaching adipose-fin spine when depressed. Dorsal-fin base
length greater than dorsal–adipose distance. Adipose fin stout, angled up from body, membrane visible beneath
spine. Pectoral spine stout, moderately long, reaching past pelvic-fin base but not to cloaca. Anal fin small but well
developed; base of first anal-fin pterygiophore exposed, anal-fin origin posterior to vertical through base of last
dorsal-fin ray. Pelvic fins reaching well past anal-fin origin, inserted at vertical through second branched dorsal-fin
ray. Caudal fin truncate, lower lobe slightly longer than upper.
Tiny odontodes present on body plates, largest on posterior margins of plates. All fin spines with small
odontodes, more developed in pectoral-fin spine of males. All fin rays with tiny odontodes on rays.
Meristics (N=60). Mid-dorsal plates 16–18, x̃ = 16; median plates 22–24, x̃ = 23; mid-ventral plates 17–18, x̃ =
18; plates bordering dorsal-fin base seven to eight, x̃ = eight; plates between dorsal and adipose fins six to seven, x̃
= six; preadipose plates 1. Fin-ray formulae: dorsal II,7–8, x̃ II,7; pectoral I,6; pelvic i,5; anal i,3–4, x̃ = i,4; caudal
i,14,i. Caudal procurrent spines dorsal: three to five, x̃ = 5; ventral: three to four, x̃ = three.
Sexual dimorphism. (Fig. 5a) Snout tentacles of nuptial males long, largest 1.5 times eye diameter.
Posteromedial tentacles diverging in V-shape along anteriorly triangular snout plates. Naked areas of snout without
tentacles rugose, separated from naris by several, wide plates; naked area narrow, distance from anteromedial plate
to snout less than distance from anteromedial plate to line formed between anterior edges of nasal apertures.
Color in alcohol. (Fig. 18) Base color of all fins, dorsum, sides and ventrum of body black, brown or gray,
with tiny white dots; dots often lost in preservative. First dorsal-fin membrane dark black near its base.
Life colors. (Fig. 1) Body and fins jet black with tiny white dots. First dorsal-fin membrane dark black near its
base.
Distribution: Present in Guyana in both the Essequibo River Basin and tributaries of the Amazon River Basin
(such as the Takutu) as well as the Cuyuni River of Venezuela (Fig. 7).
Remarks. This fish can reach a very large size for an Ancistrus, over 138 mm SL. The largest species known,
A. maximus reaches around 200 mm SL (Oliveira et al., 2015), shares a similar color pattern, and is likely closely
related to A. nudiceps. Oliveira et al. imply that the species differ by A. maximus having eight branched dorsal-fin
rays (vs. seven). Eight is rare in other Ancistrus, but two specimens of A. nudiceps from the Cuyuni River were
found to have eight branched dorsal-fin rays. Preliminary results of DNA analysis detected no significant
differences among populations of A. nudiceps from rivers of the Essequibo and Amazon basins in Guyana or the
Cuyuní River in Venezuela. Although there is about 12% divergence between A. nudiceps and A. patronus new
species based on these preliminary Cyt b analysis.
Ancistrus patronus, new species
(Figs. 19–20)
Holotype. MCNG 56681 (ex AUM 39876) (1, 83.6 mm SL), male, Venezuela, Amazonas, Orinoco River Basin,
Ventuari River at mouth of Camoni creek, 145 km NNE of Macaruco, 189 km NE of San Fernando de Atabapo,
5.05588, -66.32742, 8-Apr-2004, M. Sabaj, N. Lujan, D. Werneke, L. de Souza, and O. León.
Paratypes. All from Venezuela, Orinoco River Basin: Amazonas State: ANSP 160236 (1, 74.3 mm SL), creek
15 km E Parguaza River ferry crossing on Caicara-Puerto Ayacucho hwy, 6.35946, -67.05375, 28-Nov-1985, B.
Chernoff, W. Saul, C. Marrero, R. Royero; AUM 39271 (6, 5, 50.8–86.0 mm SL), Parucito River, at raudales
Salomon, 2.7 km NE of San Juan de Manapiare, Ventuari/Manapiare drainage, 5.34637, -66.03347, 16 April 2004,
D. Werneke, N. Lujan, O León-Mata; ANSP 205667 (4, 57.9–75.7 mm SL); AUM 39306 (7, 5, 62.4–86.0 mm SL),
Manapiare River14.5 km NW of San Juan de Manapiare, Ventuari River drainage, 5.42863 -66.13616, 12-Apr-
2004, N. Lujan, M. Sabaj, L. de Souza, D. Werneke; AUM 39876 (4, not measured), same data as holotype; ANSP
205668 (3, 60.3–66.8 mm SL); AUM 40189 (6, 1, 60.1 mm SL), tributary to Orinoco River, 30 km S of Puerto
Ayacucho, 5.38659, -67.61556, 1-Apr-2004, D. Werneke, N. Lujan, L. de Souza, O. Leon Mata, M. Sabaj; AUM
40578 (1, 74.7 mm SL), Orinoco River at Macuruco landing, 3.95816, -067.03231, 4-Apr-2004, M. Sabaj, L. de
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Souza, D. Werneke, N. Lujan; AUM 41324 (2, 1, 77.9 mm SL), Manapiare River 14 km NW San Juan de
Manapiare, 5.43704, -66.11408, 13-Apr-2004, M. Sabaj, N. Lujan, D. Werneke, L. de Souza; AUM 41494 (1, 71.3
mm SL), Ventuari River drainage, Manapiare River at mouth of Yutaje creek, 14 km NW of San Juan de
Manapiare, 5.43667, -66.11261, 11 Apr-2004, M. Sabaj, L. de Souza, D. Werneke, N. Lujan; AUM 42176 (1, 71.5
mm SL), Casiquiare River drainage, Siapa River at rapids, 154 km E of San Carlos de Rio Negro, 1.60339, -
65.71587, 11-Mar-2005, M. Sabaj, L. de Souza, D. Werneke, N. Lujan; AUM 43572 (3, 2, 52.3–65.1 mm SL),
Casiquiare/Siapa River drainage, Guama creek draining Cerro Derecha, 16-Mar-2005, N. Lujan, D. Werneke, M.
Sabaj, M. Arce-Hernández, R. Betancur; AUM 43868 (1, 79.4 mm SL), Caño Soromoni, 11.8 km E of La
Esmeralda, 3.19380, -65.65197, 26-Mar-2005, N. Lujan, M. Arce-Hernández, L. Richmond, B. Grant, E. Wesley;
AUM 53894 (1, not measured), Parucito River at raudales Solomon, Manapiare River, Ventuari River drainage,
5.34648, -66.03328, V. Meza, O. Santaella, and N. Lujan, 11-Apr-2010; AUM 54088 (1, not measured), Ventuari
River, cobble shoal ~1 km upstream of Moriche, 167 km ENE of San Fernando de Atabapo, 4.75346, -66.37260,
N. Lujan, D. Werneke, M. Sabaj, T. Carvalho, O. Leon, V. Meza, 3-Apr-2010; AUM 54420 (1, not measured),
Manapiare River at Manapiare landing, 173.8 KM ESE of Puerto Ayacucho, Ventuari River drainage, 5.32864, -
66.05067, J. Birindelli, O. Léon, 13-Apr-2010; AUM 54313 (1, not measured), Marueta creek, 159 km E of San
Fernando de Arabapo, 4.29481, -66.28888, N. Lujan, M. Sabaj, D. Werneke, T. Carvalho, V. Meza, 2-Apr-2010.
INHS 61554 (3, 58.2–79.6 mm SL), stream near Pozo Azul, 5.763219, -67.489034, 21-Jan-1992, L. Page, L. Nico,
P. Ceas, J. Lyons; MCNG 38168 (1 of 3, 86.0 mm SL), Agua Linda creek, 0.5 km upper waters between Puerto
Ayacucho and Caicara, approx. 30 km north of Puerto Ayacucho, 5.645368, -67.456057 24-Jan-1998; MCNG
50038 (3, 64.8–73.0 mm SL), Manapiare River, 14.5 Km al NW de San Juan de Manapiare, 5.428611, -66.136111,
4-Dec-2004; UF 77841 (1, 42.5 mm SL), Ventuari River at Tencua, just below Tencua Falls, 5.050752, -65.625381
20-Mar-1981, S. Reid, C. Gilbert. Apure State: AUM 22631 (10, 5, 54.5–87.87 mm SL) Potrerito creek, ca.15 km
N Puerto Paez on road to San Fernando, 6.41194, -67.53194, 26-Dec-1999, collectors: J. Armbruster, M. Hardman,
J. Evans, J. Thomas; Bolivar State: AUM 22336 (1, 46.2 mm SL), 6.31583, -67.09611, Ore creek, ca. 50 km SW
Los Pijiguaos, Caicara-Puerto Ayacucho road., 25-Dec-1999, J. Armbruster, M. Hardman, J. Evans, J. Thomas.
Diagnosis. Ancistrus patronus differs from all other Ancistrus in the region except A. lithurgicus, A.
macrophthalmus, A. maximus and A. nudiceps by having an entirely black body with tiny white to golden dots;
from A. leoni by having the abdomen almost as dark as the sides (vs. much lighter); from A. nudiceps by reaching a
much smaller maximum size (86 vs.138 mm SL), by having the distance between the anteromedial plate and the
snout greater than or equal to the distance between the anteromedial plate and a line formed by the anterior margins
of the nasal apertures (vs. less than); and from A. leoni, A. lithurgicus, and A. macrophthalmus by being deep-
bodied (vs. flattened), by having the median plate below the posterior edge of the adipose-fin membrane about
twice as tall as wide (vs. just slightly taller than), and by the eyes being laterally placed (vs. dorsolaterally placed in
A. lithurgicus and almost completely dorsally placed in A. macrophthalmus.
Description. Morphometrics given in Table 5. Size range this study: 43–86 mm SL. A relatively large, robust
Ancistrus, body broadest anteriorly, greatest body width near opercles, usually at base of pectoral spines, but
sometimes body slightly wider near middle of pectoral-spine length in fish with plump abdomens, thence
narrowing progressively to end of caudal peduncle. Head and body not very depressed, greatest body depth just
anterior to dorsal-fin origin. Caudal peduncle deep, robust, compressed posteriorly. Dorsal profile of head steeply
ascending through length of soft snout, then continuing in gentle concave arc to tip of supraoccipital process where
it then descends to dorsal-fin origin and continues its decline to point below tip of adipose-fin spine; then angled up
through dorsal procurrent caudal-fin spines. Ventral profile of mouth flat to beneath pectoral-fin insertions, then
slightly concave to pelvic-fin insertions, then almost straight to lower caudal-fin spine.
Head wide, interorbital width about equal to head depth, much more than half of head length. Snout rounded
with large broad naked margin in males, less wide in females and juveniles. Snout length more than one-half head
length. Eye large, interorbital area slightly convex. Oral disk ovate, wider than long. Lips covered with minute
papillae, larger near mouth. Lower lip moderate in size, not reaching gill aperture, its border covered with very
small papillae. Maxillary barbel very short, its length less than orbit diameter. Jaws short with premaxillary tooth
rows forming strong arc and dentary tooth rows forming angle of >135°. Dentary and premaxillary tooth rows
strongly curved medially, lateralmost dentary tooth medial to lateralmost premaxillary tooth. Teeth small and
numerous (58–120 per jaw ramus), asymmetrically bifid, medial cusp much larger and spatulate, lateral cusp
minute and pointed, usually not reaching more than half length of medial cusp, but equal in worn teeth.
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ANCISTRUS NORTHWESTERN GUIANA SHIELD ORINOCO ANDES
FIGURE 19. Ancistrus patronus, holotype, in dorsal, lateral, and ventral views, AUM 39876, 83.6 mm SL. Scale = 1 cm.
Photos by J.W. Armbruster.
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FIGURE 20. Live coloration of head of Ancistrus patronus in dorsal and lateral views, AUM 43868, 79.4 mm SL. Scale = 1
cm. Photos by N.K. Lujan.
Hypertrophied cheek odontodes strongly evertible, nine to 19, stout with tips hooked anteriorly, bases encased
in thick fleshy sheaths. Exposed part of opercle roughly triangular, covered with short stout odontodes. Head
smooth, bones on back of head not carinate; supraoccipital with margins between surrounding bones and plates
usually clearly visible. Lateral plates not carinate.
Ventral surface of head and abdomen naked, no exposed platelets anterior to anal-fin spine. Nuchal plate small
and curved posterolaterally. Enlarged odontodes present along edges of lateral plates. Five series of lateral plates
anteriorly, three series on caudal peduncle, mid-dorsal and mid-ventral plate series end on caudal peduncle beneath
adipose fin. Last plate in median series much smaller than penultimate plate, and median plate below end of
adipose fin about twice as high as wide. Base of caudal fin with about eight roughly triangular platelets covering
bases of caudal-fin rays.
Dorsal-fin origin situated anterior to vertical through pelvic-fin insertion. First dorsal-fin ray not elongate, but
longer than snout length; last dorsal-fin ray reaching adipose-fin spine when depressed. Dorsal-fin base length
much longer than dorsal–adipose distance. Adipose fin stout, angled up from body, membrane visible beneath
spine. Pectoral spine stout, moderately long, reaching just past pelvic-fin base but not to cloaca. Anal fin small but
well developed; base of first anal-fin pterygiophore covered by skin, anal-fin origin posterior to vertical through
base of last dorsal-fin ray. Pelvic fins reaching well past anal-fin origin but not past anal-fin tip, inserted at vertical
about through second branched dorsal-fin ray. Caudal fin truncate, lower lobe slightly longer than upper.
Tiny odontodes present on body plates, largest on posterior margins of plates. All fin spines with small
odontodes, more developed in pectoral-fin spine of males. All fin rays with tiny odontodes on rays.
Meristics (N=47). Mid-dorsal plates 6–18, x̃ = 13; median plates 22-24, x̃ = 23; mid-ventral plates 16–19, x̃ =
17–18; plates bordering dorsal-fin base 4–8, x̃ = 7; plates between dorsal and adipose fins 4–8 median 6–7;
preadipose plates one. Fin-ray formulae invariate: dorsal I,7; pectoral I,6; pelvic i,5; anal i,4; caudal i,14,i. Caudal
procurrent spines: dorsal: four to five, x̃ = five; ventral: two to four, x̃ = three.
Sexual dimorphism. (Fig. 5b) snout tentacles of nuptial males long, largest 1.5 times eye diameter.
Posteromedial tentacles diverging in V-shape along anteriorly triangular snout plates. Naked areas of snout without
tentacles rugose, separated from naris by several, wide plates; naked area wide, distance from anteromedial plate to
snout greater than or equal to distance from anteromedial plate to line formed between anterior edges of nasal
apertures.
Color in alcohol. (Fig. 19) Base color of all fins, dorsum, sides and ventrum of body black, brown or gray,
with tiny white dots; dots often lost in preservative. First dorsal-fin membrane with dark pigment near base. Upper
and lower tips of caudal fin sometimes white or cream colored.
Life colors. (Fig. 20) Body and fins jet black with tiny white dots. First dorsal-fin membrane with dark
pigment near base. Upper and lower tips of caudal fin sometimes white or cream colored.
Distribution. Present in the upper río Orinoco from the río Cinaruco upstream and the río Casiquiare (Fig. 7).
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ANCISTRUS NORTHWESTERN GUIANA SHIELD ORINOCO ANDES
Etymology. Named for good fathers. Patronus is Latin for protector or defender and is derived from pater for
father. Males of this genus guard their nests and protect their young until they are fairly large. With their cheek
odontodes everted, males can block off nests and potentially injure predators.
Ancistrus saudades new species
(Figs. 21–22)
Holotype. CSBD F 1722 (1, 107.48 mm SL) Rupununi, Guyana, Region 9, Amazon/Branco/Takutu River, creek at
second wooden bridge from Moco-Moco power station, 13-Nov-2007, 3.30318
o
, -59.65038
o
. L. de Souza, D.
Taphorn, J. Baskin, T. Geerinckx and J. Hawn.
Paratypes. Guyana, Region 9, Amazon/Branco River Basin: AUM 35631 (16, 7, 70.2–96.0 mm SL),
Rupununi, Takutu River drainage, Yuora River, tributary of the Ireng River, 6.7 km NE Karasabai, J. Armbruster,
M. Sabaj, D. Werneke, C. Allison, M. Thomas, C. Chin, D. Arjoon 31-Oct-2002; AUM 35633 (20, 9, 44.3–83.2
mm SL), Rupununi, Takutu River drainage, Sauriwau River 31.2 km NW village of Sand Creek, 3.11432
o
,-
59.77544
o
, J. Armbruster, M. Sabaj, D. Werneke, C. Allison, M. Thomas, C. Chin, D. Arjoon, 4-Nov-2002; AUM
35634 (18, 4, 60.7–79.1 mm SL), Rupununi, Moco-Moco creek at Moco-Moco hydropower station, 18.8 km SE of
Lethem, 3.29672
o
, -59.64466
o
, J. Armbruster, M. Sabaj, D. Werneke, C. Allison, M. Thomas, C. Chin, D. Arjoon,
5-Nov-2002; AUM 37989 (6, 3, 46.3–77.9 mm SL), Rupununi, Kumu Creek 15.2 km SE of Lethem 3.25953
o,
, -
59.72373
o
, J. Armbruster, M. Sabaj, M. Hardman, D. Arjoon, N. Lujan, L. de Souza, 2-Nov-2003; AUM 48283
(32, 2, 65.0–73.45 mm SL), Rupununi, Takutu River drainage, Moco-Moco Creek at Moco-Moco hydropower
station, 18.8 km SE of Lethem, 3.29663
o
, -59.64507
o
, L. de Souza, D. Taphorn, J. Baskin, T. Geerinckx and J.
Hawn, 13-Nov-2007; AUM 48587 (6, 2, 62.6–73.5 mm SL), Rupununi, Takutu River drainage, first creek
downstream of Moco-Moco Creek at power station, 3.30095
o
, -059.64908
o,
L. de Souza, D. Taphorn, J. Baskin, T.
Geerinckx and J. Hawn, 13-Nov-2007; AUM 50020 (24, 3, 68.4–75.6 mm SL), same data as holotype; FMNH
69963 (1, 48.8 mm SL) Moco Moco River behind hostel at St. Ignacius, 3.35886, -59.78959, 15-Dec-1968.
Guyana, Region 8, Amazon/Branco River Basin: AUM 67043 (2, not measured), Takaika Creek, left bank
tributary of Ireng River that enters below lower Orinduik Falls, 4.72366, -60.03062, local fishermen, 2-Jan-2016;
AUM 67055 (5, not measured), Tumong Creek, left-hand tributary of Ireng River, 4.71388, -60.02234, N. Lujan, J.
Armbruster, D. Werneke, M. Ram, 3-Jan-2016; AUM 67104 (4, 0), Tumong Creek, left-hand tributary of Ireng
River, 4.71971, -60.01311, D. Werneke, N. Lujan, J. Armbruster, M. Ram, 6-Jan-2016;
Non-types. Guyana, Region 9, Amazon River Basin: FMNH 53090 (1, 75.6 mm SL), Ireng River, near
“Holmia” (this is likely an error as Holmia is in the upper Potaro River Basin, not the Ireng, excluded from type
series because of uncertain locality), 1908; Venezuela, Orinoco River Basin (excluded from type series): ANSP
146219 (2, 51.0–96.0 mm SL) Caura River drainage, Cuchima creek (Cusimi River), ca 20 mi upstream from
junction of Caura River with Erebato River (between rivers), 5.71208, -64.55980, 7-Feb-1977; AUM 36663 (4,
60.6–72.5 mm SL), Caroní River drainage, Samey River, 57.5 km WSW of Santa Elena, 6 km S. of El Piaje, on
foot path, 4.124336, -61.043975, 14-Jun-2003; AUM 39477 (3, 44.0–61.3 mm SL), Ventuari River, above Salto
Tencua, 58 km ESE of San Juan de Manapiare, 5.04777, -65.61583, 21-Apr-2004; FMNH 110066 (1, 77.0 mm
SL), Caura River drainage, creek near its mouth with upper Caura, River at Cejiato, 5.55780, -64.31360, 28-Nov-
00; FMNH 110069 (1, 51.2 mm SL), Caura River drainage, Creek at Tojanaño that flows into Tawadu River,
6.33750, -65.02500, 5-Dec-00; MCNG 12071 (1, 63.9 mm SL), Caura, Creek a tributary of Guana River,
4.159326, -63.749342, 26-Oct-1982; MCNG 20877 (2, 52.0–62.6 mm SL), Caura River drainage, Nichare River in
a rivulet behind a small island, 6.22972, -64.93861, 19-Mar-1989; MCNG 23201 (2, 42.9–60.7 mm SL), Caura
River drainage, Nichare River, slabs near Serapia creek, Bolivar state, 6.55000, -64.85000, 25-Mar-89; MCNG
48095 (5, 57.0–64.0 mm SL), Rio Samey, 57 Km al WSW de Santa Elena 4.42278, -61.59583, 14-Jun-2003; UF
78052 (1, 61.2 mm SL), Caura River drainage, confluence of río Erebato with Caura (several localities in
immediate area), 5.93159, -64.42734, 23-Mar-1981.
Diagnosis. Ancistrus saudades differs from all other Ancistrus in the region except A. brevifilis, A.
leucostictus, and A. triradiatus by having large spots on the caudal fin, abdomen, and sides (these can be obscured
in preserved specimens, but spots generally remain in the fins, vs. all dark color with small white dots, dots may be
absent in preserved specimens). Ancistrus saudades can be separated from A. leucostictus by having the adpressed
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dorsal fin reaching maximally to the middle of preadipose plate (vs. to middle of the adipose-fin spine or beyond)
and by having the pectoral-fin spine when adpressed ventral to the pelvic fin not reaching the base of the cloacal
tube (vs. reaching the base of the cloacal tube in adults) and by having relatively smaller light spots and wider dark
interspaces on the anterolateral plates and posterodorsal head bones with the interspaces half to equal in width to
the spots or spots not visible in this region in preserved specimens (vs. spots relatively large with the interspaces
much less than half the size of the interspaces and at least some spots in this region visible in all specimens; the
difference in spots vs. interspaces generally works on the abdomen as well); from A. brevifilis by having round
spots on the caudal fin (vs. oval spots), and from A. brevifilis and A. triradiatus by having spots on the abdomen in
life (vs. spots absent; rare specimens of A. triradiatus have spots).
FIGURE 21. Ancistrus saudades, holotype, in dorsal, lateral, and ventral views, CSBD F 1722, 107.5 mm SL. Scale = 1 cm.
Photos by J.W. Armbruster.
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TABLE 6. Morphometric features of Ancistrus saudades n. sp. (N =56, except
1
N=55) and triradiatus (N=194, except
2
N=193 and
3
N=189).
Description. Morphometrics given in Table 6. Size range of examined specimens 42.9–107.48 mm SL. A
medium sized Ancistrus, body broadest anteriorly, greatest body width just posterior to opercles, then narrowing
progressively to end of caudal peduncle. Head and body depressed, greatest body depth between level of pectoral-
A. saudades n. sp. A. triradiatus
Feature Avg. SD Min Max Avg. SD Min Max
SL (mm) 64.6 12.8 42.9 107.5 67.2 15.6 37.4 107.2
% SL
Predorsal Length 47.3 1.7 44.3 52.6 47.7 2.0 43.6 53.8
Head Length 37.5 1.5 34.5 42.3 38.4 2.1 33.8 45.7
Head-dorsal Length 9.9 1.1 7.8 13.3 9.8 1.2 6.9 13.6
Cleithral Width 31.4 1.6 27.5 34.4 32.6 1.7 28.7 37.1
Head-pectoral Length 28.7 1.4 25.6 33.4 29.1 2.1 23.8 37.2
Thorax Length 25.4 1.5 20.4 29.1 24.5 2.0 20.2 32.6
Pectoral-spine Length 33.4 2.1 28.3 39.5 31.6 2.6 24.6 38.8
Abdominal Length 22.2 1.2 19.5 26.1 22.2 1.4 18.7 34.4
Pelvic-spine Length 25.7 1.3 22.7 28.5 25.7 1.6 20.3 33.3
Postanal Length 30.9 1.3 27.0 33.1 31.4 1.8 26.7 36.6
Anal-fin spine Length 9.2
1
0.9 7.4 11.0 10.2
2
1.4 6.4 16.7
Dorsal-pectoral Distance 28.8 1.1 27.0 31.1 29.0 1.4 21.5 33.8
Dorsal spine Length 28.6
1
2.0 24.9 33.2 28.2
3
1.9 21.7 34.5
Dorsal-pelvic Distance 20.7 1.9 15.0 24.3 21.4 2.1 14.3 27.4
Dorsal-fin base Length 23.9 1.7 19.4 27.4 24.1
2
1.4 20.2 28.8
Dorsal-adipose Distance 17.6 1.4 15.2 23.0 17.2
3
1.6 13.4 21.9
Adipose-spine Length 8.3
1
1.1 5.9 10.6 7.9
2
1.3 0.0 11.1
Adipose-up. caudal Distance 13.4 1.2 10.9 15.8 13.8 1.6 10.0 18.9
Caudal peduncle Depth 10.4 0.8 8.0 12.1 10.4 1.0 8.2 13.3
Adipose-low. caudal Distance 19.7 1.1 17.5 22.3 19.8 1.3 16.9 23.4
Adipose-anal Distance 19.7 1.2 17.4 22.7 20.1 1.3 16.9 23.2
Dorsal-anal Distance 14.5 0.7 12.6 16.5 15.0 1.2 12.5 18.3
Pelvic-dorsal Distance 23.3 1.8 19.4 27.0 24.6
2
1.8 19.4 30.0
% Head Length
Head-eye Length 40.5 2.0 35.2 44.0 40.2 2.5 33.7 47.6
Orbit Dia. 17.8 1.5 13.9 22.0 16.6 2.2 11.6 21.7
Snout Length 58.9 2.5 53.7 64.9 57.6 2.6 51.3 64.6
Internares Width 20.4 1.5 17.0 23.8 19.7 1.7 14.4 23.5
Interorbital Width 57.9 2.4 51.0 62.1 55.9 3.3 46.3 63.4
Head Depth 62.5 2.8 55.5 68.5 63.0 3.2 53.4 71.7
Mouth Length 49.7 3.2 43.3 57.9 48.5 3.5 39.1 60.9
Mouth Width 52.4 4.4 41.2 59.7 53.1 4.7 41.6 67.4
Barbel Length 4.9 1.5 1.8 8.0 4.9 1.8 0.7 11.8
Dentary tooth cup Length 14.4 1.9 10.3 18.9 16.2 2.4 10.6 22.5
Premaxillary tooth cup Length 15.7 2.3 10.2 19.6 16.7 2.4 11.1 23.3
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fin insertions and dorsal fin origin. Caudal peduncle deep, robust, compressed posteriorly. Dorsal profile of head
ascending steeply in convex arc from tip of snout to just posterior of orbits, ascending in straight line to posterior
tip of supraoccipital, then descending to dorsal-fin origin. From the dorsal-fin origin descending in a slight convex
arc to just posterior of dorsal-fin base, then straight to caudal fin. Ventral profile flat to slightly convex from tip of
snout to pelvic-fin insertions. Abdomen flat to slightly concave to pelvic-fin insertions, from there, straight to
slightly convex and sloping gently ventrally towards caudal fin.
FIGURE 22. Live coloration of Ancistrus saudades in dorsal and lateral views, AUM 67055, 58.1 mm SL. Scale = 1 cm.
Photos by N.K. Lujan.
Head wide, interorbital width equal or slightly less than head depth, slightly less than half of head length.
Snout rounded with large broad naked margin in males, less wide in females and juveniles. Snout length about one-
half head length. Eye moderate in size, interorbital area slightly convex. Oral disk ovate, wider than long. Lips
covered with minute papillae, larger near mouth. Lower lip moderate in size, not reaching gill aperture, its border
covered with very small papillae. Maxillary barbel very short, its length less than orbit diameter. Jaws short with
premaxillary tooth rows forming strong arc and dentary tooth rows forming angle of >135°. Dentary and
premaxillary tooth rows strongly curved medially, lateralmost dentary tooth medial to lateralmost premaxillary
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tooth. Teeth numerous (49–120 per jaw ramus), asymmetrically bifid, medial cusp much larger and spatulate,
lateral cusp minute and pointed, usually not reaching more than half length of medial cusp, equal in worn teeth.
Hypertrophied cheek odontodes strongly evertible, eight to 14, stout with tips hooked anteriorly, bases encased in
thick fleshy sheaths. Exposed part of opercle small, roughly triangular with few odontodes.
Head smooth, bones on back of head not carinate; supraoccipital with margins between surrounding bones and
plates usually clearly visible. Lateral plates not carinate, lateral line pores distinctly visible, horizontally elongate.
Ventral surface of head and abdomen naked, no exposed platelets anterior to anal-fin spine. Nuchal plate small
and curved posterolaterally. No enlarged odontodes at edge of lateral plates. Five series of lateral plates anteriorly,
three series on caudal peduncle, mid-dorsal and mid-ventral plate series ending on caudal peduncle beneath
preadipose plate just anterior to embedded adipose-fin spine. Last plate in median series slightly smaller than
penultimate plate, and median plate below end of adipose fin about twice as high as wide. Base of caudal fin with
six platelets covering bases of caudal-fin rays.
Dorsal-fin origin situated anterior to vertical through pelvic-fin insertion. First dorsal-fin ray elongate, just
slightly longer than snout length; last dorsal-fin ray reaching first preadipose plate when depressed. Adipose-fin
spine (if present) embedded, oriented parallel to horizontal axis of body, membrane present, not visible beneath
spine. Pectoral spine long and stout, when adpressed ventrally not reaching to the cloaca. Anal fin small but well
developed; base of first anal-fin pterygiophore covered by skin, its origin below or posterior to vertical through
base of last dorsal-fin ray. Pelvic fins reaching well past anal-fin origin, inserted posterior to vertical through first
branched dorsal-fin ray. Caudal fin truncate, lower lobe longer than upper. Tiny odontodes present on body plates,
largest on posterior margins of plates. All fin spines with small odontodes, more developed in pectoral-fin spine of
males. All fin rays with tiny odontodes on rays.
Meristics (N=56). Mid-ventral plates 17; median plates 22–25, x̃ = 23; mid-dorsal plates 12–19, x̃ = 16; plates
bordering dorsal-fin base six to eight, x̃ = seven; plates between dorsal and adipose fins four to seven, x̃ = six;
preadipose plates one. Fin-ray formulae invariable: dorsal II,7; pectoral I,6; pelvic i,5; anal i,4; caudal i,14,i.
Caudal procurrent spines: dorsal: two to five, x̃ = five; ventral: two to four, x̃ = three.
Sexual dimorphism. Snout tentacles of nuptial males long, largest over twice eye diameter. Posteromedial
tentacles diverging in V-shape along anteriorly triangular snout plates. Naked areas of snout without tentacles
rugose, separated from naris by several, wide plates; naked area wide, distance from anteromedial plate to snout
greater than or equal to distance from anteromedial plate to line formed between anterior edges of nasal apertures.
Color in alcohol. (Fig. 21) Dorsal and lateral base color dark gray or brown mottled with light brown spots on
top of head and body. Plateless area of snout and tentacles also dark with irregular lighter spots. All fins with
alternating dark and light spots. Ventral surface of head and abdomen tan to yellowish tan, oral disk yellowish,
plates of ventral surface of caudal peduncle with posterior margins darker brown, forming alternating light and
dark pattern. Small white spots on ventral surface of head and abdomen. Dark interspaces on the head, anterior
body, and abdomen usually greater than half the width of the spots.
Life colors. (Fig. 22) Dorsum mottled dark and light brown with small white spots on the extent of the body.
Body posterior to dorsal-fin origin equally spotted, and base color is dark and light brown. Preadipose plate and
vestiges of adipose-fin spine outlined in yellow. Sides with irregular light and dark spots. Ventrum of body with
light brown base color and tightly spaced small white spots. Oral disk and adjacent area on chest pink to whitish.
Fin membranes lightly pigmented, grayish, but spines and rays tan in color with spots on all fins. Dark interspaces
on the head, anterior body, and abdomen usually greater than half the width of the spots.
Distribution. Ancistrus saudades has a distribution that matches the upper portion of the Proto-Berbice River
drainages: Takutu, upper Ventuari, upper Caura, and upper Caroni river drainages of Guyana, Venezuela, and
Brazil (Fig. 7). Type locality was restricted to the Takutu drainage of Guyana/Brazil because the Orinoco
populations may be distinct.
Etymology. The Portuguese word saudades is used word saudades, used to express a deep longing or
profound melancholy attached to a person, place or experience. It has a deeper tone and meaning than a direct
English translation and reflects the lead author’s connection to her Brazilian heritage and her nostalgia for field
work in remote wilderness areas that yielded these museum collections.
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Ancistrus trinitatis (Günther, 1864)
(Figs. 23–24)
Chaetostomus trinitatis Günther, 1864: 246. Type locality: Trinidad. Syntypes: based on specimens reported on by Gill (1858:
409) as Ancistrus guacharote, possibly deposited at USNM, but whereabouts unknown. See Comments below.
Ancistrus maracasae Fowler, 1946: 2, figs. 1–4. Type locality: Maracas River, Trinidad.
Neotype: ANSP 71723 (1, 82.0 mm SL), Maracas River, 29-Jun-1930, L. Wehekind, also holotype of A.
maracasae. Neotype of Chaetostomus trinitatis Günther, by present designation.
Other specimens examined. All from Trinidad. INHS 40105 (1, 78.8 mm SL), Cumuto River, 5 km S Brazil
on road to Talparo, St. George County, 29-Jan-1997, L. Page, C. Ronto; MCNG 8202 (2, 73.8–81.1 mm SL,
Guanapo River, 23-Jun-1983; MCNG 8260 (1, 56.1 mm SL), Caño Antigua, 23-Jun-1983; ROM 87569 (3, 62.2–
64.0 mm SL), Arima River, just downstream of Verdant Vale by Blachiseusse Rd., about 150 m of stream;
10.68022, -61.2903723, 23-Apr-2010; ROM 88768 (7, 68.3–96.8 mm SL), Maracas River, upstream of bridge at
Maracas; 10.68427, -61.41032, 21-Apr-2010, H. Lopez-Fernandez, J. Gilliam, D. Bloom, D. Taphorn, E. Holm;
ROM 88881 (4, 38.6–75.3 mm SL), Maracas River at El Tucuche, #1 Acono junction by playground; 10.69475, -
61.40714, 21-Apr-2010, H. Lopez-Fernandez, J. Gilliam, D. Bloom, D. Taphorn, E. Holm, D. Phillips.
Diagnosis. Ancistrus trinitatis can be separated from all other species in the region except A. brevifilis, A.
leucostictus, and A. saudades by having large light spots or blotches on the dorsal and caudal fins; from all
Ancistrus in the region by having black spots centered on the caudal-fin rays basally and white spots centered on
the rays distally (vs. tiny white or yellow spots randomly placed, or large white spots centered on the membranes);
from A. brevifilis by having the spots on the caudal fin generally smaller and better organized into rows (vs. at least
some spots on the caudal fin combining across rows and running about half the length of the caudal fin); and from
A. brevifilis, A. leucostictus, A. saudades, and A. triradiatus by lacking spots only on the dorsal fin rays (vs. spots
centered on membranes).
Description. Morphometrics given in Table 4. A large-sized Ancistrus, largest specimen examined 96.8 mm
SL. Body broadest anteriorly, greatest body width just posterior to opercles, then narrowing progressively to end of
caudal peduncle. Head and body depressed, greatest body depth near posterior margin of supraoccipital. Caudal
peduncle deep, compressed posteriorly. Dorsal profile of head ascending in arc to just behind supraoccipital and
then descending to dorsal fin. From the dorsal-fin origin descending straight or in slightly concave arc to caudal fin.
Ventral profile flat to from tip of snout to pelvic-fin insertions, from there, in concave arc to base of caudal fin.
Head wide, interorbital width equal or slightly less than head depth, slightly less than half of head length.
Snout rounded with large broad naked margin in males, less wide in females and juveniles. Snout length more than
one-half head length. Eye small, interorbital area convex. Oral disk round, just slightly wider than long. Lips
covered with minute papillae, larger near mouth. Lower lip moderate in size, not reaching gill aperture, its border
covered with very small papillae. Maxillary barbel very short, its length less than orbit diameter. Jaws short with
premaxillary tooth rows forming strong arc and dentary tooth rows forming angle of ≤135°. Dentary and
premaxillary tooth rows strongly curved medially, lateralmost dentary tooth medial to lateralmost premaxillary
tooth. Teeth numerous (40–110 per jaw ramus), asymmetrically bifid, medial cusp larger and spatulate, lateral cusp
smaller, pointed, usually not reaching more than half length of medial cusp but almost equal in worn teeth.
Hypertrophied cheek odontodes strongly evertible, nine to 15, stout with tips hooked anteriorly, bases encased in
thick fleshy sheaths. Exposed part of opercle small, roughly triangular with larger odontodes along free edge. Head
smooth, bones on back of head not carinate; supraoccipital with margins between surrounding bones and plates
usually clearly visible. Lateral plates not carinate, lateral line pores not easily visible.
Ventral surface of head and abdomen naked, no exposed platelets anterior to anal-fin spine. Nuchal plate small
and curved posterolaterally. Odontodes enlarged along edges of lateral plates. Five series of lateral plates
anteriorly, three series on caudal peduncle, mid-dorsal plate series variable in length, often ending below third or
fourth plate posterior to dorsal-fin base; mid-ventral plate series usually reaching first preadipose plate or adipose
spine. Last plate in median series about same size as penultimate plate, and median plate below end of adipose fin
about twice as high as wide. Base of caudal fin with up to twelve small platelets covering bases of caudal-fin rays.
Dorsal-fin origin situated slightly anterior to vertical through pelvic-fin insertion. First dorsal-fin ray not
elongate, much longer than snout length nearly as long as head; last dorsal-fin ray reaching first preadipose plate
when depressed. Adipose-fin spine curved, stout, not embedded, oriented at angle to horizontal axis of body,
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FIGURE 23. Ancistrus trinitatis in dorsal, lateral, and ventral views, MCNG 8202, 73.8 mm SL. Scale = 1 cm. Photos by J.W.
Armbruster.
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FIGURE 24. Live coloration of Ancistrus trinitatis in dorsal and anterodorsal views, ROM 88768, 97 mm SL. Photo by D.C.
Taphorn.
membrane present, easily visible beneath spine. Pectoral spine long and stout, when adpressed ventrally reaching
between posterior margin of pelvic-fin bases and the cloaca, which we categorize as medium distance. Anal fin
small but well developed; first anal-fin pterygiophore covered by skin, its origin well posterior to vertical through
base of last dorsal-fin ray. Pelvic fins reaching well past anal-fin origin, about half way out length of fin, inserted
posterior to vertical through base of first branched dorsal-fin ray. Caudal fin truncate, lower lobe longer than upper.
Tiny odontodes present on body plates, largest on posterior margins of plates. All fin spines with small odontodes,
more developed in pectoral-fin spine of males. All fin rays with tiny odontodes on rays.
Meristics (N=19). Mid-ventral plates 16–21, x̃ = 19; median plates 22–25, x̃ = 23; mid-dorsal plates 16–21, x̃ =
18; plates bordering dorsal-fin base five to nine, x̃ = eight; plates between dorsal and adipose fins four to nine, x̃ =
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seven; preadipose plates one. Fin-ray formulae invariable: dorsal II,7; pectoral II,6; pelvic i,5; anal i,4; caudal
i,14,i. Caudal procurrent spines: dorsal: five; ventral: two to four, x̃ = three.
Sexual dimorphism. Snout tentacles of nuptial males long, largest greater than two times eye diameter.
Posteromedial tentacles diverging in broad U-shape along anteriorly rounded snout plates. Naked areas of snout
without tentacles rugose, separated from naris by several, wide plates; naked area wide, distance from anteromedial
plate to snout greater than distance from anteromedial plate to line formed between anterior edges of nasal
apertures.
Color in alcohol. (Fig. 23) Body dark brown, slightly lighter ventrally. Medium white spots on the sides very
obscure. Alternating dark and light spots centered on all fin rays. In the dorsal fin, the dark spots may extend onto
the membranes as chevrons posteriorly. Dark spots on a light background present at the base of the caudal fin
progressing into light spots on a light background about one third length of fin. Medium-size light spots generally
visible on abdomen, dark insterpaces more than twice width of spots.
Life colors. (Fig. 24). Body almost black, covered with medium-size light spots on all surfaces. Spots on sides
very diffuse, starting behind eye, spots more intense on fins. Alternating black and white spots centered on all fin
rays. Membranes generally hyaline, but dark spots extend as chevrons posterodistally on dorsal fin, and may extend
onto rays in pelvic fin. Spots diffuse on anteroproximal portion of dorsal fin; dark spot present at base of dorsal-fin
spine and first branched ray. Caudal fin with black spots on light background anteriorly progressing to light spots
on dark background at about one third length of fin. Abdomen charcoal with light abdominal spots intense, random
in shape, not circular; dark insterspaces more than twice width of spots.
Distribution. Distributed in the northwest corner of the island of Trinidad (Fig. 7).
Comments. There is confusion over the name to apply to the Ancistrus from Trinidad. Günther (1864)
described Chaetostomus trinitatis based on Ancistrus guacharote sensu Gill (1858), but there is little in either
description to readily identify what the species is. Ancistrus guacharote is now recognized as Lasiancistrus
guacharote, and it was determined that the original locality of the type (Puerto Rico) was in error and the species
was from the Maracaibo Basin of Venezuela (Armbruster, 2005). Specimens were potentially available of C.
trinitatis at USNM, but the only loricariids deposited by Gill from the island of Trinidad are specimens of
Hypostomus robinii Valenciennes, 1840, which is the only other species of loricariid known from the island.
Günther’s (1864) description does indicate that the cheek region has evertible odontodes, which means that the
species cannot be H. robinii. Fowler (1946) described A. maracasae from the Maracas River of Trinidad, and we
believe that this and A. trinitatis are synonymous. In order to solve the taxonomic confusion, we have chosen to
recognize the holotype of A. maracasae as the neotype of A. trinitatis.
Ancistrus triradiatus Eigenmann 1918
(Figs. 25–27)
Ancistrus triradiatus Eigenmann, 1918: 680. Type locality: Quebrada Cramalote [probably a misspelling of Gramalote],
Villavicencio; Andes east of Bogotá [upper Meta River drainage, Colombia]. Holotype: CAS 60164 (illustrated in
Eigenmann 1922: 224, pl.13, figs. 3–4).
Specimens examined. Colombia. Orinoco River Basin: ANSP 80468 (1, 47.5 mm SL), Río Meta drainage,
Villavicencio. 4.15788, -73.62552, 1931; ANSP 131665 (1, 59.2 mm SL), Hacienda Humacita, Caño Angosturas at
and just below hacienda at Humacitas, 22-Feb-1972; ANSP 133129 (1, 53.3 mm SL), Meta River drainage,
Tributary of Caño La Raya, 1 km N of La Siberia, 4.08333, -73.08333; 24-Mar-1975; ANSP 163445 (2, 68.9–88.5
mm SL), Caño el Guio, 3.95, -73.15, 17–Mar-1973; ANSP 163449 (2, 47.0–69.4 mm SL), Caño El Viento, Finca
El Viento S of Matazul, 4.13333, -72.65, 18-Mar-1973; ANSP 163452 (1, 86.3 mm SL), Hacienda Humacita, small
stream flowing generally south, presumably the Lake Mozambique complex, 3.95799, -73.05453, 21-Feb-1972;
CAS 60165 (4, 42.8–66.7 mm SL), Quebrada Cramalote [a misspelling of Gramalote], at Villavicencio, 4.14592, -
73.64503; CZUT–IC 6302 (1, 66.4 mm SL), Orotoy River, Station 4: Approximately 100 m upstream of the old
dump site on the bridge on the Orotoy River on hwy of Castilla La Nueva that leads to Pozos de Acacias, 3.86936,
-73.637, 2-Dec-2010; CZUT–IC 6398 (3, 55.5–80.1 mm SL), Orotoy River, Station 3: Waters below the
Chichimene bridge, after the confluence with San Francisco creek, 29-Nov-2010; CZUT–IC 6584 (1, 83.3 mm
SL), Orotoy River, Station 3: Waters below the Chichimene bridge, after the confluence with San Francisco creek,
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25-Mar-2010; CZUT–IC 6658 (1, 75.1 mm SL), Orotoy River, Station 1: Waters upstream of the confluence with
Pajuil creek, at the entrance in front of the aqueduct in the township of San Juanito, 3.93576, -73.81287, 10-Sep-
2010; CZUT–IC 7024 (3, 51.7–66.5 mm SL), Orotoy River, Station 7: Orotoy River, approximately 50 m
downstream of Rancho Alaska, township Barroblanco (Castilla la Nueva), 3.84294, -73.49494, 8-Sep-2010;
CZUT–IC 7060 (1, 48.2 mm SL), Orotoy River, Station 5: Aprox. 200 m downstream of old dump site of
Ecopetrol, 3.8683, -73.62921, 9-Sep-2010; FMNH 58558 (3, paratypes, 38.5–61.8 mm SL), Gramalote creek,
Villavicencio, 4.15733, -73.62792, 27-Mar-2005; FMNH 94777 (1, 49.6 mm SL), 22 km E of Villavicencio in a
gallery forest on finca La Libertad, 4.14857, -73.45851, Jun–78; IAvHP 2220 (1, 103.4 mm SL), no precise
locality data probably at bridge near town of San Juan de Arama, 3.37014, -74.02949, 27-Mar-73; IAvHP 5129 (1,
73.2 mm SL), Dpto. Meta, near town of Granada, 3.66667, -74.16667, 5-Feb-2005; IAvHP 5140 (1, 95.6 mm SL),
Dpto. Meta, near town of Granada, 3.66667, -74.16667, 5-Feb-2005; IAvHP 5141 (3, 73.3–97.1 mm SL), Dpto.
Meta, near town of Granada, Caño Sardinata, sitio Bocas vía La Carpa, inspección Puerto Caldas, 3.47522, -73.72,
5-Feb-2005; IAvHP 6999 (1, 69.8 mm SL), Dpto. Vichada, Mcpo. Cumaripo, playa rocoso, Río Tomo, 5.37806, -
67.85222, 30-Jan-2004; IAvHP 8532 (1, 93.1 mm SL), Dpto. Meta, Acacías, Caño San Luis inspección San Isidro,
3.76667, -73.3, 1–Aug–06; IAvHP 8533 (3, 71.7–79.4 mm SL), Dpto. Meta, Acacías, Caño Hondo, upstream from
Guamaral, 3.91667, -73.83333, 1–Aug–06; ICN 1173 (4, 61.6–94.6 mm SL), Dpto. Meta, Río Acacias in Acacias,
3.97352, -73.76651, 26-Feb-1987; ICN 1190 (2, 81.7–91.4 mm SL), Dpto. Meta, Villavicencio, Caño Rosablanca,
Sistema Río Metica, 4.0197, -73.638, 27-Jan-1971; ICN 1192 (4, 68.6–107.2 mm SL), Dpto. Meta, Quebrada
Gramalote near Villavicencio, 4.14592, -73.64503, 1-Jan-1968; ICN 1469 (1, 76.7 mm SL), Dpto. Cundinamarca,
Río Guayuriba/Meta, 10 km al S de Rincón de Pompeya, 4.01879, -73.4339, 17-Dec-1987; ICN 3461 (1, 89.7 mm
SL), Dpto. Meta, Quebrada Gramalote, near Villavicencio, 4.14592, -73.64503, 1-Jan-1968; IUQ 2908 (2, 51.3–
63.4 mm SL), Dpto. Meta, Cano Piedra en la via Vista Hermosa–Pto. Lucas, 3.09417, -73.7825; UF 26019 (2,
54.7–60.6 mm SL), Tributary of Yucao River ca 4.7 km W of Puerto Gaitan, 4.31468, -72.12849, 5-Jan-1973; UF
33478 (1, 67.0 mm SL), Tributary of Yucao River ca 4.7 km W of Puerto Gaitan, 4.31468, -72.12849, 5-Jan-1973;
UF 33479 (0), Tributary of Yucao River ca 4.7 km W of Puerto Gaitan, 4.31468, -72.12849, 5-Jan-1973; UF 33480
(4, 64.9–88.3 mm SL), Tributary of Yucao River ca 4.7 km W of Puerto Gaitan, 4.31468, -72.12849, 5-Jan-1973;
UF 33569 (2, 52.7–64.0 mm SL), Tributary of Yucao River ca 4.7 km W of Puerto Gaitan, 4.31468, -72.12849, 8-
Jan-1973; UF 33653 (1, 51.4 mm SL), Roadside creek E of Macarena Mountain 9.6 km NE of Vistahermosa,
3.20135, -73.66437, 10-Jan-1973; USNM 120095 (1, 104.1 mm SL), Dpto. Meta, Acacias, 3.97378, -73.76707;
Colombia, Amazon River Basin: IAvHP 9139 (2, 64.8–65.7 mm SL), Dpto. Amazonas, Quebrada afluente del
Calderón, 45 minutos N of Estación Zafire, -3.97778, -69.89222, 13-Dec-2005; IUQ 968 (1, 61.8 mm SL), Zanjón
Picudo Km 7 en la via Villa Garzón - San José de Fragua, 1.08793, -76.62714, 10-Dec-1997; IUQ 1059 (1, 57.5
mm SL), Caquetá, Río Fragua, 1.33404, -75.97766, 13-Dec-1997; IUQ 1765 (1, 50.9 mm SL), Caquetá, Quebrada
tributary of Río Yurayaco, pueblo Yurayaco, near Villa Garzón, 1.03333, -76.66667, 16-Dec-1997;
Venezuela. Orinoco River Basin: ANSP 160148 (1, 78.8 mm SL), Estado Bolivar, Caño Caiman at crossing
of Caicara–Puerto Ayacucho Highway, 19.2 km W of Ciudad Bolivar–Caicara Hwy., 7.35472, -66.26458, 29-Nov-
1985; ANSP 160770 (1, 74.3 mm SL), Estado Bolivar, Morichal, 27 km from Pto. Ayacucho on hwy. to Caicara,
5.84368, -67.45471, 15-Nov-1985; ANSP 165826 2 41.4–42.2 mm SL), Estado Apure, Cinaruco/Caño Potrerito,
ca. 24 km S Río Cinaruco, on road to San Fernando de Apure, 6.41667, -67.53333, 11-Nov-1989; ANSP 166766
(1, 59.3 mm SL), Estado Anzoátegui, near Soledad, Laguna Tineo, 8.19111, -11.46894, 30-May-1988; ANSP
171089 (1, 51.7 mm SL), Estado Bolivar, Río Aro, Salto El Pájaro, 7.7434, -64.17152, 2-Nov-1988; ANSP 185268
(1, 47.9 mm SL), Estado Bolivar, Río Orocopiche, ca.15 km from mouth in Río Orinoco, downstream from Route
19 bridge, 8.05, -63.66667, 3-Nov-1979; AUM 5691 (2, 62.7–84.1 mm SL), Estado Portuguesa, Caño Maraca,
Guanare–Guanarito road at road km 60, 8.8275, -69.345, 17-Dec-1999; AUM 22190 (1, 80.1 mm SL), Estado
Táchira, Río Quinimari in Santa Ana, 6 road km from Hwy. 5, 7.665, -72.25111, 21-Dec-1999; AUM 22243 (1,
39.9 mm SL), Estado Bolivar, Caño San Felipe, 22 km SW Caicara on road to Puerto Ayacucho, 7.46991, -
66.18156, 24-Dec-1999; AUM 22297 (1, 70.6 mm SL), Estado Bolivar, Río Chaviripa, on Caicara–Puerto
Ayacucho road, 7.1325, -66.49889, 24-Dec-1999; AUM 22312 (1, 93.5 mm SL), Estado Bolivar, Río Chaviripa, at
base of falls, ca. 2 km SE Caicara–Puerto Ayacucho road, 7.11389, -66.47306, 25-Dec-1999; AUM 22554 Estado
Apure, Caño Guárico, ca.38 km S Bruzual on road to Elorza, 7.71306, -69.33056, 29-Dec-1999; AUM 22631 (6,
54.5–87.8 mm SL), Estado Apure, Caño Potrerito, ca. 15 km N Puerto Páez on road to San Fernando de Apure,
6.41194, -67.53194, 26-Dec-1999; AUM 22750 (1, 37.4 mm SL), Estado Apure, Caño La Pastora, on road to
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ANCISTRUS NORTHWESTERN GUIANA SHIELD ORINOCO ANDES
UNELLEZ módulo, 7.44444, -69.43472, 28-Dec-1999; AUM 22829 (3, not measured), Estado Portuguesa, Caño
Maraca, Guanare–Guanarito road at road km 60, 8.8275, -69.345, 1-Jan-2000; AUM 36437 (1, 75.3 mm SL),
Estado Bolívar, Río Paragua/Caroní drainage, Río Chiguao, 19.4 km E. of La Paragua, 6.7892, -63.15871, 8-Jun-
2003; AUM 36554 (3, 50.8–86.2 mm SL), Estado Bolívar, Río Claro, 50.5 km SE of Ciudad Bolívar, 7.92358, -
63.11528, 10-Jun-2003; AUM 39894 (9, 68.9–80.2 mm SL), Orinoco Delta, Caño Mánamo near Coporito,
8.91667, -62.0, 5-Apr-1980; AUM 42972 (1, 53.6 mm SL), Río Orinoco at Puerto Venado, 4.3 km S of Samariapo,
56.4 km SSW of Puerto Ayacucho, 5.2106, -67.80495, 26-Feb-2005; AUM 54016 (1, 0), Estado Portuguesa,
Quebrada Ajaque, 18.6 km W of Guanare, at via Las Panelas, 9.08294, -69.91548, 15-Mar-2010; AUM 54047 (5,
not measured), Caño Las Panelas, Balneario Las Panelas via a las Cruces, 20.4 km W of Guanare, 9.09286, -
69.93016, 15-Mar-2010; FMNH 45709 (1, 80.4 mm SL), Estado Bolivar, Chimantá–tepui, Río Abacapa Camp 1,
altitude 1300 m, 5.27629, -62.19496, 4-Apr-1953; INHS 27675 (1, 88.4 mm SL), Estado Apure, Caño Potrerito,
hwy. bridge between San Fernando and Puerto Páez, 6.41333, -67.53222, 22-Jan-1992; INHS 27764 (1, 104.7 mm
SL), Estado Barinas, Caño Curito at Hwy. 5, 7.9735, -71.00833, 7-Jan-1992; INHS 30006 (1, 63.9 mm SL), Estado
Barinas, Caño Hondo, Agua Negra, 8.5752, -69.80073, 14-Jan-1993; INHS 31411 (1, 64.1 mm SL), Estado
Anzoátegui, Río Tigre, near El Tigre, (Caño Mánamo Dr.), 8.896603, -64.147740, 6-Jan-1994; INHS 34732 (1,
72.5 mm SL), Estado Barinas, Río Curito (Río Suripá drainage, 8 km NE San Antonio on Hwy. 5, 7.91028, -
71.08222, 3-Feb-1995; INHS 36333 (1, 62.7 mm SL), Estado Guárico, Río Aguaro, 8.05167, -66.42611, 10-Jan-
1995; INHS 36334 (1, 77.6 mm SL), Estado Guárico, Río Aguaro, 15 km S of Paso Cachimbo, 7.96668, -
66.42963, 10-Jan-1995; INHS 55532 (1, 57.5 mm SL), Estado Bolívar, Río Chaviripa, on Caicara - Pto. Ayacucho
Rd., 7.1325, -66.49889, 24-Dec-1999; INHS 61322 (1, 61.2 mm SL), Estado Barinas, Río Bum Bum in Bum Bum,
8.27294, -70.77155, 10-Jan-1992; INHS 61353 (1, 79.4 mm SL), Estado Portuguesa, Caño Maraca, 8.88633, -
69.48833, 13-Jan-1992; MCNG 5568 (5, 55.1–88.8 mm SL), Barinas state, creek near Emalca, after the alcabala in
the culvert, 8.15833, -70.60139, 12-Sep-1982; MCNG 6033 (1, 71.4 mm SL), Apure state, Terecay creek, 35 Km
north on the highway towards the Módulos de Apure, 7.83889, -69.31667, 18-Mar-1981; MCNG 6151 (2, 63.4–
74.4 mm SL), Portuguesa state, Maraca creek, hwy Guanare– Guanarito, 8.83056, -69.33611, 23-Jan-1981;
MCNG 6618 (2, 77.7–77.7 mm SL), Táchira state, creek north of Burgua River via El Nula (west of Arenoso
creek), 7.46389, -71.96389, 28-May-1982; MCNG 7139 (2, 54.6–57.1 mm SL), Barinas state, Socopó Viejo River,
Ticoporo forest, Emelca plot, 7.98333, -70.59167, 4-Oct-1993; MCNG 9618 (2, 58.8–78.5 mm SL), Balsa creek in
Las Margaritas [probably in Barinas State, but record states Apure], 7.29722, -70.73333, 16-Mar-1979; MCNG
9976 (1, 59.4 mm SL), Barinas state, Camburito River, 7.78056, -71.58194, 26-Oct-1998; MCNG 18586 (1, 40.0
mm SL), Bolívar state, Caroní, El Muerto creek near Hato Mata Linda, 7.79444, -63.28611, 3-Sep-1988; MCNG
26793 (1, 56.5 mm SL), Barinas state, Bum Bum River near town of Bum Bum, 8.27257, -70.77147, 1-Oct-1992;
MCNG 33807 (5, 57.8–71.1 mm SL), Apure State, Sardina creek, at the entrance of the city of Sucre, 7.09639, -
71.89889, 25-May-1996; MCNG 39521 (1, 59.7 mm SL), Apure state, Cinaruco River, behind the Piedras del
Caimán, 6.54583, -67.41667, 18-Jan-1999; MCNG 41858 (not measured), Portuguesa state, Las Marías River,
near Guanare, 9.40278, -69.7375, 1998; MCNG 42795 (1, 57.2 mm SL), Bolívar state, Chivaripa Rive on the
highway Caicara–Puerto Ayacucho, 7.13222, -66.49861, 24-Dec-1999; MCNG 48095 (not measured), Bolívar
state, Samey River, 57 km WSW of Santa Elena of Uairen, 4.42278, -61.59583, 14-Jun-2003; UF 33908 (2, 66.7–
84.6 mm SL), Portuguesa state, Tucupido River in Las Canoas above dam site, near Guanare, 8.9411, -69.83145,
18-Mar-1982; UF 80451 (1, 58.1 mm SL), Bolívar state, Bridge of Río Chaviripa on Caicara–San Fernando de
Atabapo Puerto Ayacucho, road, 7.13349, -66.50209, 16-Apr-1984 (day); UF 80499 (1, 42.6 mm SL), Bolívar
state, Bridge of Río Chaviripa on Caicara–San Fernando de Atabapo Puerto Ayacucho, road, 7.13349, -66.50209,
16-Apr-1984 (night).
San Juan and Morichal Largo Basins: INHS 31469 (1, 43.0 mm SL), Estado Monagas, Río Guanipa 20 km
SSE Maturin, Hwy. 10, 9.58075, -63.12397, 8-Jan-1994; MCNG 28970 (1, 45.8 mm SL), Tigre River near El
Tigrito, 8.92722, -64.18639, 1-Jun-1994; MCNG 29118 (2, 42.7–52.3 mm SL), Monagas state, Guanipa River at
the bridge on the road 5 km south of Aguasay, 9.36833, -63.77972, 1-Jul-1994; MCNG 29187 (1, 51.2 mm SL),
Monagas state, River of Oro below bridge southeast of Jusepín, 9.8125, -63.81389, 1-Jul-1994; MCNG 48466 (1,
53.8 mm SL), Sucre state, Manzanares River along the road of Arenas and Cedeño, 10.30306, -63.97306, 18-Dec-
1998; MCNG 29754 (1, 60.6 mm SL), Sucre state, National Park Península de Paria, Maraval River, Las Melenas
sector, 10.63889, -62.475, 25–Aug–92; MCNG 19452 (2, 49.0–53.3 mm SL), Sucre state, tributary San Juan River
towards Santa Rosa, south of Casanay, 10.43333, -63.45, 14–Aug–88; UF 80716, (1, 62.3 mm SL), Monagas state,
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Caripito creek, 10.12395, -63.12744, 17-Apr-1984; INHS 31447 (1, 52.2 mm SL), Monagas state, Guarapiche
River (San Juan, 4 km SW Jusepin, 9.00141, -63679121, 7-Jan-1994.
Lake Valencia Basin: FMNH 35342 (2, 85.5–106.7 mm SL), Aragua state, Turmero river, near town of
Turmero, 10.22946, -67.4796, 24-Sep-1937; FMNH 35357 (1, 68.3 mm SL), Aragua state, Turmero river, near
town of Turmero, 10.22174, -67.49644, 24-Sep-1937.
FIGURE 25. Ancistrus triradiatus in dorsal, lateral, and ventral views, MCNG 8199, 77.7 mm SL. Scale = 1 cm. Photos by
J.W. Armbruster.
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FIGURE 26. Live coloration Ancistrus triradiatus in lateral view. Uncataloged, Quebrada Aqua Blanca, río Cusiana - río Meta
Draianage, 05.00656°, -072.78792°. Photo by A. Urbano-Bonilla.
Diagnosis. Ancistrus triradiatus can be separated from all other species in the region except A. brevifilis, A.
leucostictus, and A. saudades by having large light spots or blotches on the dorsal and caudal fins; from A. brevifilis
by having the spots on the caudal fin generally smaller and better organized into rows (vs. at least some spots on the
caudal fin combining across rows and running about half the length of the caudal fin); and from A. leucostictus and
A. saudades by almost always lacking spots on the abdomen (vs. spots almost always present). Some specimens of
A. triradiatus have spots on the abdomen and they are larger than the interspaces (vs. smaller in A. saudades) and
they are less numerous than in A. leucostictus with the interspaces about half the width of the spots (vs. much less
than half the width of the spots in A. leucostictus). Ancistrus triradiatus is replaced in Amazonian drainages with A.
malacops (Cope, 1872), which always has well-developed spots on the abdomen, but is otherwise very similar and
may be conspecific. Ancistrus triradiatus and A. gymnorhynchus are sympatric in the Río Pao system of northern
Venezuela. Specimens of A. triradiatus from the Pao can be separated from A. gymnorhynchus by having black
spots on the fins and at least faint white spots on the body (vs. body entirely brown except for occasionally light
spots at the ends of the unbranched caudal-fin rays, which are also in A. triradiatus in the Pao).
Description. Morphometrics given in Table 6. A medium-sized Ancistrus, largest specimen examined 107 mm
SL. Body broadest anteriorly, greatest body width just posterior to opercles, then narrowing progressively to end of
caudal peduncle. Head and body depressed, greatest body depth near posterior margin of supraoccipital. Caudal
peduncle deep, compressed posteriorly. Dorsal profile of head ascending steeply to above eye, then ascending in
convex arc to dorsal-fin origin. From the dorsal-fin origin descending straight or in slightly concave arc to caudal
fin. Ventral profile flat to from tip of snout to pelvic-fin insertions, from there, in concave arc to base of caudal fin.
Head wide, interorbital width equal or slightly less than head depth, slightly less than half of head length.
Snout rounded with large broad naked margin in males, less wide in females and juveniles. Snout length more than
one-half head length. Eye small, interorbital area convex. Oral disk round, just slightly wider than long. Lips
covered with minute papillae, larger near mouth. Lower lip moderate in size, not reaching gill aperture, its border
covered with very small papillae. Maxillary barbel very short, its length less than orbit diameter. Jaws short with
premaxillary tooth rows forming strong arc and dentary tooth rows forming angle of >135°. Dentary and
premaxillary tooth rows strongly curved medially, most lateral dentary tooth medial to most lateral premaxillary
tooth. Teeth numerous (41–120 per jaw ramus), asymmetrically bifid, medial cusp larger and spatulate, lateral cusp
smaller, pointed, usually not reaching more than half length of medial cusp but almost equal in worn teeth.
Hypertrophied cheek odontodes strongly evertible, nine to 23, stout with tips hooked anteriorly, bases encased in
thick fleshy sheaths. Exposed part of opercle small, roughly triangular with larger odontodes along free edge. Head
smooth, bones on back of head not carinate; supraoccipital with margins between surrounding bones and plates
usually clearly visible. Lateral plates not carinate, lateral line pores not easily visible.
Ventral surface of head and abdomen naked, no exposed platelets anterior to anal-fin spine. Nuchal plate small
and curved posterolaterally. Odontodes enlarged along edges of lateral plates. Five series of lateral plates
anteriorly, three series on caudal peduncle, mid-dorsal plate series variable in length, often ending below third or
fourth plate posterior to dorsal-fin base; mid-ventral plate series usually reaching first preadipose plate or adipose
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spine. Last plate in median series about same size as penultimate plate, and median plate below end of adipose fin
about twice as high as wide. Base of caudal fin with up to twelve small platelets covering bases of caudal-fin rays.
FIGURE 27. Some of the diversity present in Ancistrus triradiatus. A. Specimen from the lower Río Caroni showing a lateral
body color similar to A. leucostictus and an abdomen with very slight spotting, AUM 36554, 86.2 mm SL. Photos by J.W.
Armbruster. B. Specimen from southwestern Venezuela in dorsal view with short pectoral fins, AUM 22190, 80.1 mm SL.
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Dorsal-fin origin situated slightly anterior to vertical through pelvic-fin insertion. First dorsal-fin ray not
elongate, much longer than snout length nearly as long as head; last dorsal-fin ray reaching first preadipose plate
when depressed. Adipose-fin spine curved, stout, not embedded, oriented at angle to horizontal axis of body,
membrane present, easily visible beneath spine. Pectoral spine long and stout, when adpressed ventrally reaching
between posterior margin of pelvic-fin bases and the cloaca, which we categorize as medium distance. Anal fin
small but well developed; first anal-fin pterygiophore covered by skin, its origin well posterior to vertical through
base of last dorsal-fin ray. Pelvic fins reaching well past anal-fin origin, about half way out length of fin, inserted
posterior to vertical through base of first branched dorsal-fin ray. Caudal fin truncate, lower lobe longer than upper.
Tiny odontodes present on body plates, largest on posterior margins of plates. All fin spines with small odontodes,
more developed in pectoral-fin spine of males. All fin rays with tiny odontodes on rays.
Meristics (N=194). Mid-ventral plates 15–20, x̃ =17; median plates 21–24, x̃ = 22; mid-dorsal plates nine to
20, x̃ = 16; plates bordering dorsal-fin base five to eight, x̃ = seven; plates between dorsal and adipose fins four to
eight, x̃ = seven; preadipose plates one to two, x̃ = one. Fin-ray formulae: dorsal II,7; pectoral II,6; pelvic i,5; anal
i,2–4, x̃ = i,4; caudal i,14,i. Caudal procurrent spines: dorsal: four to five, x̃ = five; ventral: two to four, x̃ = three.
Sexual dimorphism. Snout tentacles of nuptial males long, largest greater than two times eye diameter.
Posteromedial tentacles diverging in broad U-shape along anteriorly rounded snout plates. Naked areas of snout
without tentacles rugose, separated from naris by several, wide plates; naked area wide, distance from anteromedial
plate to snout greater than distance from anteromedial plate to line formed between anterior edges of nasal apertures.
Color in alcohol. (Figs. 25 and 27) The expression of the light spots on the body, and the dark spots on the fins
in this species is quite variable. Eigenmann (1918:680) pointed out that the juveniles were differently patterned
from adults: “body including head and belly, with faint, roundish, light spots; dorsal with about five series of
comma-shaped black spots in broken series lengthwise of the fin; caudal with similar but shorter spots which
merge into two continuous bars at the base; pectorals and ventral with similar but larger spots, those of successive
rays alternating, outer angles of caudal light. In other specimens sometimes the tip of the first two dorsal rays, and
in the young the margin of the caudal light, the markings on the fins confined to the rays. Ventral surface in the
small specimens plain.” Water quality, altitude, courting and spawning activities and other parameters probably all
play a role in determining the expression of their color pattern. In alcohol the base color is brown with the dorsum
darker than the ventrum. All fins usually have rows of dark spots that variably align into rows or arcs, but the
pigment is not always restricted to the rays, as noted by Eigenmann, but extends onto the membranes. Populations
appear to vary geographically in the intensity of the expression of the fin spots. Those from around the type locality
in Colombia in the upper Río Meta are usually well marked, those from Venezuelan Andean streams often less so,
and those from the llanos and Guiana Shield watershed usually have some of the darkest spotting. But non-
conforming individuals appear among all these populations. The light spots on the body are similarly variably
expressed, usually lacking on fish from Venezuelan Andean streams, but present elsewhere. Faint, light, abdominal
spots found in some specimens from the Río Meta drainage, Orinoco Delta, and lower Caroni. Guiana Shield
specimens tend to have larger spots on sides and head similar to those of A. leucostictus, but this color fades to
common A. triradiatus color from east to west.
Life colors. (Fig. 26). Male: Base color of dorsum of head and body brown, pale whitish and greenish
irregularly-shaped spots, of varying sizes (the largest greater than pupil, the smallest about half that, many run
together) present on soft snout including tentacles, top of head between and behind eyes to posterior margin of
supraoccipital. Posterior to the head bones spots poorly defined on dermal plates on top of body, but present, and
mixed with darker brown irregular markings in front of and along sides of dorsal fin, dark pigment intensifying
lateral to posterior part of dorsal fin and on dorsum of caudal peduncle to form four dark saddles (first at level of
anterior part of dorsal fin, second at posterior part of dorsal fin base, running together with third centered anterior
to adipose fin, fourth behind adipose-fin base. Sides of body marked similarly to adjacent portions of dorsum.
Spines of dorsal, pectoral, pelvic, adipose and caudal fins with five or six alternating light and dark sections with
similar markings mirrored on all fin rays, to form rows of dark and light spots. Spines of pectoral and pelvic fins
very dark overall. Female: Base color brown, with dark dorsal saddles as in male, but no light-colored spots
anywhere on dorsum. Pectoral, pelvic, dorsal and caudal fin spines and rays with only very faint alternating light
and dark sections.
Distribution. Distributed throughout the Orinoco River and Lake Valencia drainages, but replaced in the
higher elevations of the Guiana Shield by A. saudades (Fig. 7).
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Comments. Ancistrus triradiatus is likely to represent several species. Specimens from the Guiana Shield tend
to be colored more similarly to A. leucostictus with the few specimens available from the lower Caroni having
large, but very faint, spots on the abdomen (Fig. 27A). These specimens appear to grade into typical A. triradiatus
in the west, however. Specimens in streams that drain into the Orinoco Delta and from streams that drain to the
Caribbean directly, specimens from the Meta, and rare specimens in the Venezuelan llanos may have small, faint,
light spots on the abdomen. Eigenmann (1918) describes the species as having spots on the abdomen, but Fowler
(1943) states that the specimens he had available lacked spots. One of the paratypes does have very faint spots
laterally on the abdomen, but none centrally located.
In addition, there are several specimens from the southwest corner of Venezuela that have particularly short
pectoral fins and a lighter color than typical A. triradiatus (Fig. 27B). We did not have enough specimens to
determine if these were a variant or a different species.
Ancistrus gymnorhynchus is a species generally limited to the coastal drainages of Venezuela (the Tocuyo,
Aroa, Yaracuy, Urama rivers and other small drainages), but are also present in the Río Pao, Orinoco River system
(Taphorn et al., 2010). The Pao specimens of A. gymnorhynchus are brown (vs. gray) and the Pao A. triradiatus
(the dot just to the west of Lago Valencia in figure 7) have less intense spots on the fins than other specimens of A.
triradiatus. It is possible that there has been introgression between the two species in this area. Unraveling further
taxonomic structure in A. triradiatus will require extensive genetic information.
Ancistrus yutajae, new species
(Fig. 28)
Holotype. MCNG 7854 (1, 82.80 mm SL) Amazonas, Venezuela, Orinoco/Ventuari/Yutajé River, Yutajé River at
the end of the airstrip at Campamento Yutajé, 6.146078
o
, -61.492243
o
14-Feb-1981, S. Reid.
Paratypes. ANSP 205666 (2, 60.3–78.4 mm SL), AUM 71045 (2, 66.6–75.8 mm SL), and MCNG 2664 (1,
62.4 mm SL) Amazonas, Venezuela, Orinoco/Ventuari/Yutajé River, Yutajé River near campamento Yutajé , 15-
Mar-1981, 5.547222
o
, -66.115833
o
, S. Reid; MCNG 41745 (4, 39.8-50.1 mm SL) Amazonas, Venezuela, Orinoco/
Ventuari/Yutajé River, Caño Yutajé near confluence of Rio Corocoro, 26-Mar-1999, 6.29835
o
,-61.531858
o
, S.
Reid.
Diagnosis. Ancistrus yutajae can be separated from all other Ancistrus in the area by having the rows of
tentacles barely diverging, almost parallel along the median line (vs. tentacles widely diverging in a V- or U-shape
to almost straight and transverse), by having a rectangular naked patch centrally posterior to tentacles and
extending to anterior margin of nares (vs. no central naked spot behind tentacles and naked area ending anterior to
anterior margin of nares, also present in A. kellerae); and by almost always having two or three branched anal-fin
rays (vs. four, one specimen of A. yutajae has four); from all except A. amaris and specimens of A. triradiatus from
the Río Orotoy of Colombia by having very long dentaries (minimum interorbital width divided by dentary length
1.24–1.76 vs. ≥1.91), and from A. amaris by having the longest tentacles of nuptial males about equal to orbit
diameter (vs. less than orbit diameter). Ancistrus yutajae differs from other Ancistrus along the Andean piedmont
with long jaws (A. bolivianus, A. bufonius, A. greeni, A. heterorhynchus, A. marcapatae, A. megalostomus, A.
occloi, A. sericeus, and perhaps A. jelksii) by having the dorsal fin reaching the preadipose plate (vs. well short), by
having the pectoral-fin spine when adpressed below pelvic fin reaching to beyond pelvic-fin base (vs. barely or not
reaching pelvic fin), and by having the body relatively deep (vs. very depressed)
Description. Morphometrics given in Table 7. A relatively small-sized Ancistrus, body broadest anteriorly,
greatest body width just posterior to opercles, then narrowing progressively to end of caudal peduncle. Head and
body depressed, greatest body depth between level of pectoral-fin insertions and dorsal-fin origin. Caudal peduncle
deep, robust, compressed posteriorly. Dorsal profile of head ascending steeply in convex arc from tip of snout to
just posterior of orbits, ascending in straight line to posterior tip of supraoccipital, then descending to dorsal-fin
origin. From the dorsal-fin origin descending in a slight convex arc to just posterior of dorsal-fin base, then straight
to caudal fin. Ventral profile flat to slightly convex from tip of snout to pelvic-fin insertions. Abdomen flat to
slightly concave to pelvic-fin insertions, from there, straight to slightly convex and sloping gently ventrally
towards caudal fin.
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TABLE 7. Morphometric features of Ancistrus yutajae n. sp. (N =10).
Head wide, interorbital width equal or slightly less than head depth, slightly less than half of head length.
Snout rounded with large broad naked margin in males, less wide in females and juveniles. Snout length about one-
half head length. Eye small in size, interorbital area slightly convex. Oral disk ovate, wider than long. Lips covered
with minute papillae, larger near mouth. Lower lip moderate in size, not reaching gill aperture, its border covered
with very small papillae. Maxillary barbel very short, its length less than orbit diameter. Jaws long with
A. yutajae n. sp.
Feature Avg. SD Min Max
SL (mm) 60.6 15.4 39.9 82.8
% SL
Predorsal Length 50.9 2.2 46.0 54.0
Head Length 41.6 1.2 39.5 43.4
Head-dorsal Length 9.9 1.2 8.7 12.6
Cleithral Width 35.2 1.0 34.0 37.4
Head-pectoral Length 32.0 1.2 30.3 34.0
Thorax Length 23.9 0.9 22.6 25.1
Pectoral-spine Length 29.7 1.7 26.2 31.7
Abdominal Length 23.0 1.1 21.2 24.9
Pelvic-spine Length 25.4 0.6 24.6 26.3
Postanal Length 30.5 1.1 29.1 32.3
Anal-fin spine Length 8.6 1.1 7.1 10.4
Dorsal-pectoral Distance 30.2 1.2 28.0 32.0
Dorsal spine Length 24.6 2.4 20.5 27.6
Dorsal-pelvic Distance 19.2 1.6 16.3 21.7
Dorsal-fin base Length 23.5 1.0 21.4 24.5
Dorsal-adipose Distance 16.6 1.6 14.4 20.1
Adipose-spine Length 6.9 0.5 5.8 7.6
Adipose-up. caudal Distance 12.0 0.8 11.2 13.6
Caudal peduncle Depth 10.4 1.1 8.3 12.2
Adipose-low. caudal Distance 19.1 0.6 18.4 19.9
Adipose-anal Distance 19.3 1.4 17.3 21.3
Dorsal-anal Distance 13.8 1.0 12.4 15.2
Pelvic-dorsal Distance 24.6 1.2 22.5 26.4
% Head Length
Head-eye Length 39.0 1.3 37.4 41.1
Orbit Dia. 15.3 1.6 13.1 18.3
Snout Length 57.8 2.3 54.2 61.6
Internares Width 17.5 1.0 16.5 19.1
Interorbital Width 51.7 2.2 48.9 55.0
Head Depth 61.2 1.6 58.9 63.9
Mouth Length 51.1 3.3 46.4 55.3
Mouth Width 65.0 4.7 57.6 72.9
Barbel Length 5.5 1.6 3.3 8.1
Dentary tooth cup Length 22.9 2.7 20.3 29.1
Premaxillary tooth cup Length 22.9 1.5 20.8 26.0
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premaxillary tooth rows forming slight arc and dentary tooth rows almost straight (slightly less than 180°). Dentary
and premaxillary tooth rows moderately curved medially, lateralmost dentary tooth lateral to lateralmost
premaxillary tooth. Teeth numerous (82–145 per jaw ramus), asymmetrically bifid, medial cusp much larger and
spatulate, lateral cusp minute and pointed, usually not reaching more than half length of medial cusp, equal in worn
teeth. Hypertrophied cheek odontodes strongly evertible, 13–34, stout with tips hooked anteriorly, bases encased in
thick fleshy sheaths. Exposed part of opercle small, roughly triangular with few odontodes.
FIGURE 28. Ancistrus yutajae, holotype, in dorsal, lateral, and ventral views, MCNG 7854, 82.8 mm SL. Scale = 1 cm.
Photos by J.W. Armbruster.
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Head smooth, bones on back of head not carinate; supraoccipital with margins between surrounding bones and
plates usually clearly visible. Lateral plates not carinate, lateral line pores distinctly visible, horizontally elongate.
Ventral surface of head and abdomen naked, no exposed platelets anterior to anal-fin spine. Nuchal plate small
and curved posterolaterally. No enlarged odontodes at edge of lateral plates. Five series of lateral plates anteriorly,
three series on caudal peduncle, mid-dorsal and mid-ventral plate series end on caudal peduncle beneath preadipose
plate just anterior to embedded adipose-fin spine. Last plate in median series slightly smaller than penultimate
plate, and median plate below end of adipose fin about twice as high as wide. Base of caudal fin with five platelets
covering bases of caudal-fin rays.
Dorsal-fin origin situated anterior to vertical through pelvic-fin insertion. First dorsal-fin ray elongate, just
slightly longer than snout length; last dorsal-fin ray reaching first preadipose plate when depressed. Adipose-fin
spine (if present) embedded, oriented parallel to horizontal axis of body, membrane present, not visible beneath
spine. Pectoral spine short and stout, when adpressed ventrally rearching the insertion of the pelvic fin. Anal fin
small but well developed; base of first anal-fin pterygiophore covered by skin, its origin below or posterior to
vertical through base of last dorsal-fin ray. Pelvic fins reaching well past anal-fin origin, inserted posterior to
vertical through first branched dorsal-fin ray. Caudal fin truncate, lower lobe longer than upper. Tiny odontodes
present on body plates, largest on posterior margins of plates. All fin spines with small odontodes, more developed
in pectoral-fin spine of males. All fin rays with tiny odontodes on rays.
Meristics (N=10). Mid-ventral plates 17–19, x̃ = 18; median plates 21–23, x̃ = 22; mid-dorsal plates 14–19, x̃ =
18; plates bordering dorsal-fin base seven to eight, x̃ = seven; plates between dorsal and adipose fins six to seven, x̃
= six; preadipose plates one to two, x̃ = one. Fin-ray formulae: dorsal II,7; pectoral I,6; pelvic i,5; anal i,2–4, x̃ =
i,3; caudal i,14,i. Caudal procurrent spines: dorsal: five, ventral: three.
Sexual dimorphism. Snout tentacles of nuptial males short, largest 1.5 times eye diameter. Posteromedial
tentacles diverging in almost parallel along anteriorly triangular snout plates that are covered in thick skin. Naked
areas of snout without tentacles rugose, separated from naris by single, narrow plate; naked area wide, distance
from anteromedial plate to snout greater than distance from anteromedial plate to line formed between anterior
edges of nasal aperatures.
Color in alcohol. (Fig. 28) Base color light brown with small light dots, mostly faded. Plateless area of snout
and tentacles also light brown no spots. All fins light brown, no spots or bands. Ventral surface of head and
abdomen tan to yellowish tan with small dots, oral disk yellowish, plates of ventral surface of caudal peduncle with
posterior margins slightly darker brown, forming alternating light and dark pattern.
Life colors. Live color is unknown.
Distribution. Known only from the Yutaje River of Venezuela (Fig. 7). Despite recent collecting in the area,
no specimens other than those collected in 1981 were procured.
Etymology. Named after the Yutajé River where the holotype was collected, and in tribute to a legend of the
indigenous people of the Panare and Makiritare tribes. According to the legend, the name Yutajé commemorates Yu
and Taje, young lovers whose tribes were at war. Upon learning of their forbidden love, the Maquiritare chief
ordered their capture. On a clear moonlit night the lovers found themselves cornered on the edge of a cliff and
launched themselves into the void. In the air they invoked the god of waters, who took pity on them and turned
them into twin waterfalls, which today intermingle to form the Yutajé Falls and the Yutajé River. The legend states
that the lovers will someday return to their human forms, when their tribes unite to form a single people and
peacefully inhabit the Guiana Shield lands. Treated as a noun in the genitive case.
Discussion
Taxonomy. Ancistrus malacops is likely the Amazonian Andean piedmont version of A. triradiatus (see
Provenzano and Barriga-Salazar, 2018 for a review of the species). Anicistrus triradiatus in the southern portion of
its range has a similar color pattern in some specimens with large, light spots on the abdomen. This color pattern
fades in northern populations and topotypic specimens show both color patterns (plain abdomens and spotted
abdomens). A population genetic study across the Andean piedmont will be necessary to ascertain the species in
this range. We have seen some variation within Venezuelan and Colombian specimens, with some of the
Colombian specimens similar to A. amaris. In all likelihood, A. triradiatus represents multiple species, but more
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genetic data will be needed to guide morphological observations. Differences between A. triradiatus and A.
brevifilis are also subtle, with the colors generally more intense in A. brevifilis, and the spots tending to combine
across rows on the caudal fin (vs. forming distinct rows). This color pattern is also seen in some specimens from
the Meta.
Ancistrus amaris is likely derived from A. triradiatus. Although there are long-jawed species of Ancistrus
known from throughout the southern Andes, this is the first species from the northern Andes, and it differs by being
deeper-bodied and by having longer fins than the southern long-jawed species. Its shape is much more like A.
triradiatus, but males differ by having very small tentacles. Although it could be argued that the tentacles have not
fully developed, we have enough specimens of a large enough size that we would expect to have seen them.
Ancistrus amaris may have kept its genetic identity by being significantly different from A. triradiatus in this
critical, sexually-selected characteristic.
Ancistrus leucostictus and A. saudades are very similar, but separate by 7% sequence divergence in
cytochrome b. The differences in color pattern and fin size are subtle, but, along with the genetic data, are sufficient
in diagnosing the two species. The two collections of A. saudades from the lower Caura could be A. triradiatus, but
the specimens are small and faded, and we cannot be certain of their identity. We have examined photographs from
the upper Paragua, and the specimens are A. saudades, cataloged at MHNLS.
In their description of Ancistrus maximus, de Oliveira et al. (2015) do not expressly compare the species to the
only other species described from the Rio Branco drainage, A. nudiceps, but the two can generally be separated by
A. maximus having eight branched dorsal-fin rays (vs. seven, although two examined specimens of A. nudiceps
from the Cuyuni did have eight). The two species are similar in color pattern; however, the spot size stays very
small and separate in A. nudiceps while the spots are relatively larger in juveniles of A. maximus, and occasionally
combine to form dashes (de Oliveira et al. 2015). Although it does not reach the extreme in size of A. maximus
(200.8 mm SL), A. nudiceps is also a fairly large Ancistrus, reaching 138.4 mm SL in the specimens we examined.
Given the absence of A. nudiceps in the specimens examined by de Oliveira et al. it is likely that A. nudiceps is
replaced by A. maximus in the Rio Branco, and the capture of the Takutu by the Branco resulted in both being
present in the Branco drainage.
Also present within the rio Negro basin is Ancistrus dolichopterus (Kner, 1854). Like A. maximus, A.
dolichopterus has eight dorsal-fin rays separating it from the other species with small white to yellow spots (A.
nudiceps and A. patronus). Interestingly, colors change in A. dolichopterus upon preservation. The melanophores
around the white spots darken and take over most of the space of the white spots making it look like the specimens
have small black spots instead (Michael Hardman, pers. comm.)
The only other species de Oliveira et al. (2015) list from the Rio Negro drainage is A. cf. dubius. Ancistrus
dubius Eigenmann & Eigenmann (1889) was described as a variety of A. cirrhosus from opposite sides of the
Amazon (Gurupa at the mouth of the Amazon and Tabatinga at the border of Brazil, Colombia, and Peru). The type
images available on the All Catfishes Species Inventory website (Morris et al., 2006) are of a species similar to A.
saudades or A. leucostictus. We identified a potential specimen of A. dubius from the Peruvian Amazon (AUM
62996). The color pattern is faded in the type, but is similarly weak in AUM 62996 such that the pattern is more
subtle than in A. saudades with a spot size more similar to A. leucostictus, but the spots placed further apart;
additionally, the white spots in the dorsal fin are circular in A. dubius vs. combining to form bands in A.
leucostictus and A. saudades. The type of A. dubius has about 30 teeth per jaw ramus and AUM 62996 (80.0 mm
SL) has 36 premaxillary teeth and 45 dentary teeth. Tooth number is correlated with size, and similarly-sized
specimens of A. leucostictus and A. saudades (70 mm SL or greater) have 60–120 teeth and no examined
individuals of either species had fewer than 49 teeth. The head is also considerably wider in A. dubius than A.
leucostictus and A. saudades.
Eigenmann (1912) recognized four species not discussed here in Guyana: A. cirrhosus (Valenciennes, 1836),
A. hoplogenys (Günther, 1864), A. temminki (Valenciennes, 1840, in Cuvier & Valencinnes 1840), and A.
gymnorhynchus (Kner, 1854). Ancistrus cirrhosus is from the Paraná River basin and is not considered further here
(Fisch Muller 2003). Ancistrus gymnorhynchus is entirely brown, but it is known only from the Caribbean coast of
Venezuela west of Caracas and the upper Pao River (Orinoco River basin, see A. triradiatus account; Taphorn et
al., 2010).
Ancistrus hoplogenys is from the rio Capim, Pará, Brazil. A syntype was photographed as part of the All
Catfishes Species Inventory (Morris et al., 2006). This species is most similar to A. nudiceps and A. patronus in
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that it may have small white dots, but no dots are visible on the type photo and the fins appear that they could have
dark bands. This species appears to differ from all of the species examined herein by several features: the head is
much shorter and broader, the eye extends barely posterior to the base of the evertible cheek odontodes (vs. most or
all of the eye posterior to the bases of the cheek odontodes), and by having only two columns of three rows of
plates on the caudal peduncle beginning posterior to the adipose fin (vs. several columns of three rows of plates on
the caudal peduncle beginning under the adipose fin spine). Le Bail et al. (2000) describe an A. aff. hoplogenys
from French Guiana as being entirely brown, which is unlike any Northwestern Guiana Shield species. Provenzano
& Barriga-Salazar (2018) raise A. alga from the synonymy of A. hoplogenys. We examined a collection of large-
bodied, small-spotted species from the Amazon of Peru that would likely represent A. alga (AUM 62995 and AUM
uncat.). These specimens are very similar to A. nudiceps, except that the caudal fin is more emarginate (vs.
obliquely truncate). The large-bodied, small-spotted species of the Amazon and Essequibo definitely need greater
scrutiny across the entire range; however, A. patronus is certainly different in reaching a smaller adult size and was
not found to be sister to A. nudiceps (although support values for the tree are weak).
Ancistrus temmincki is likely from around the area of Paramaribo, Suriname (Boeseman, 1972). The holotype
was pictured and described in Bleeker (1864) as entirely reddish-brown, again, unlike any of the Northwestern
Guiana Shield species. Le Bail et al. (2000) recognize an A. aff. temmincki from eastern French Guiana, but
describe it as having spots that make the background dark color appear as a network. This sounds similar to A.
leucostictus, but the spot size in their pictured specimen in Le Bail et al. is much smaller than that of A.
leucostictus. Specimens that we have examined of an Ancistrus from the Commewijne River (that joins the
Suriname River at its mouth at Paramaribo, AUM 50779) have small, sparse white spots on the abdomen and fins
like A. nudiceps and A. patronus. However, the specimens have a lighter background color on the sides than A.
nudiceps and A. patronus and have dark saddles (vs. dorsal color uniform). In addition, the end of the caudal
peduncle of the AUM 50779 specimens has a light tan bar extending the depth of the caudal peduncle, which is
also not seen in A. nudiceps or A. patronus.
Biogeography. The dynamic geological history that influenced the ancient configuration of river drainages of
the Guiana Shield has strongly influenced the diversification of fishes there, including Ancistrus. One of the largest
rivers during the Cenozoic period was the Proto-Berbice, which flowed east-northeasterly between the eastern and
western lobes of the Guiana Shield. The extent of this ancient river included many of the paleofluvial headwaters of
the modern-day drainages of the Guiana Shield, including the Branco River, Uraricoera River, Takutu River, Ireng
River, Essequibo River, Potaro River, Cuyuni River, Corentyne River and some Orinoco tributaries (like the upper
Caroni, Caura, Erebato, and Ventuari Rivers; Lujan & Armbruster 2011). Historically, the shield region contained
the highest concentrations of high-gradient habitat available, which likely influenced the origin of rheophilic
loricariid taxa like Ancistrus. A key feature of the Proto-Berbice is the Takutu Graben, which is a rift valley
separating the eastern and western lobes of the Guiana Shield. It is centered on the town of Lethem, Guyana, and
situated between the Pakaraima and Kanuku mountains. A large endorheic lake, Lake Maracanata, occupied this
depression and was the precursor to the main-stem of the Proto-Berbice. Tectonic activity between the Cenozoic
and Pleistocene fragmented the Proto-Berbice creating a shallow divide, which is now occupied by the Rupununi
savannas. Seasonal rains flood the savannas, creating a temporary hydrological corridor between the Amazon and
Essequibo drainages, which we refer to as the Rupununi portal. This biogeographic feature has played an important
role in determining the distributions of fishes and other taxa (de Souza et al., 2012; Lovejoy & Araújo, 2000; Willis
et al., 2007; Lujan et al., 2018). We discuss the influence of the prone-8 hydrology of the Guiana Shield (Lujan &
Armbruster, 2011) on Ancistrus examined herein.
Closer examination of A. leucostictus across the Rupununi portal revealed some morphological differences and
strong molecular evidence to split it into two species: A. leucostictus and A. saudades. A. saudades is distributed
from the Takutu River to the upper Ventuari River tributaries, Caura and Caroni and this distributional pattern can
be explained by the historic connections of the Proto-Berbice. This distribution supports the idea that the upper
Orinoco tributaries used to flow south into the Proto-Berbice, and is similar to the findings of Lujan et al. (2018)
for the loricariids of the Lithoxini. Although relationships of Ancistrus should be examined with molecular data,
the current distributions suggest that uplift of the western Guiana Shield shifted the distribution of the species into
the Orinoco drainage, and that a molecular clock would provide information on the timing of this.
By contrast, molecular evidence supports the distribution of A. nudiceps across the Rupununi portal, occurring
in both the upper Branco-Amazon and Cuyuni–Essequibo River drainages. A. nudiceps long-distance dispersal
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between drainages could be explained by its tolerance to various habitats and water chemistries. This species seems
to favor more lowland areas that facilitates the ease of movement between drainages and tolerance to hypoxic
conditions. For example, A. nudiceps were collected from Long Lake, which was a muddy bottom lowland lake
uncharacteristic of most other Ancistrus species that often are found in clearwater lotic habitats (JWA pers. obs.).
Three Ancistrus species we examined are endemic to Guyana, A. leucostictus, A. lithurgicus and A. kellerae
new species. Ancistrus leucostictus and A. lithurgicus were found in river channels of the Essequibo River drainage
often associated with large boulders and fast-flowing water. Preliminary molecular evidence suggests a close
relationship between A. leucostictus and A. lithurgicus and further genetic analysis with non-mitochondrial markers
could test if this relationship suggests introgression (Fig. 4). However, given that the morphology of A. leucostictus
and A. lithurgicus is quite different while A. leucostictus and A. saudades are difficult to tell apart, we predict that
the close relationship between A. lithurgicus and A. leucostictus is a result of mitochondrial introgression.
Ancistrus kellerae new species is endemic to the highlands of Guyana in the Pakaraima Mountains, associated with
fast-flowing blackwater, large boulders and grassy shoals. Recognition of Ancistrus kellerae is of particular
importance due to the encroaching threats due to gold and diamond mining. The extent of the range of A. kellerae
is currently not known. The lower Kuribrong River is under tremendous pressure from gold mining, and, as of
2014, mines were found almost to the base of Amaila Falls.
The dorsoventrally flattened species, Ancistrus leoni and A. macrophthalmus and small white- to yellow-
spotted A. patronus new species are distributed along the Orinoco River and the Casiquiare River. The Casiquiare
connection between the Rio Negro (Amazon River drainage) and upper Orinoco has been a well-documented route
of dispersal for several fish species and likely explains A. leoni, A. macrophthalmus and A. patronus distributions
(Winemiller et al., 2008). The long-jawed species A. amaris is found sympatric with A. triradiatus in headwater
streams of the Andean piedmont of Venezuela, the furthest west among northwestern Guiana Shield Ancistrus.
Another long-jawed species A. yutajae new species is so far found only on the Yutajé-Corocoro massif of the
Guiana Shield.
Among the interesting results from this study is the distribution of A. triradiatus, ranging from the Venezuelan
Andes, Venezuela portion of the Guiana Shield and Caribbean coast. We found slight variation morphologically
across the regions, but more in-depth examination of this group is needed, and it is likely that genetic data can
distinguish between these populations. A. brevilfilis is only found from the Rio Tuy in Venezuela draining into the
Caribbean, although similar to A. triradiatus, spotting patterns and coloration is much brighter in Ancistrus
brevifilis. Ancistrus trinitatis also has a limited range in Trinidad.
Conclusion
Examination of Ancistrus taxonomy is taking an iterative approach by multiple researchers, and it will be necessary
to stitch the regional and morphotypic studies that have been done together into a cohesive picture of the genus.
Our study provides a first examination of Ancistrus in the complex landscape of the northwestern Guiana Shield.
Despite this in-depth investigation, many gaps remain in our understanding of the taxonomy of Ancistrus. As one
of the most diverse, wide-ranging genera within loricariids, there is need for more extensive sampling throughout
its range. It is also apparent through preliminary genetic analysis, that further investigation into the molecular
phylogenetics in the genus can provide insights to the diversification of this group in South America. Final
settlement of the species of Ancistrus awaits genetic and morphological studies of specimens from Brazil and other
areas not yet studied.
Acknowledgements
This project was supported by Planetary Biodiversity Inventory: All Catfish Species (Siluriformes)—Phase I of an
Inventory of the Otophysi (NSF DEB-0315963), by NSF grants DEB-0107751 and DEB-1023403 to JWA, Auburn
University, and funding from the Universidad Nacional Experimental de los Llanos Occidentales Ezequiel Zamora
that supported fieldwork for several expeditions to the upper Orinoco in Venezuela as well as the study of museum
material in Venezuela, Colombia, Guyana and the US. We are grateful to the following colleagues for hospitality
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when visiting their collections, the loan and preparation of specimens and access to database information: S.
Schaefer (AMNH); J. Lundberg, M. Sabaj, and K. Luckenbill (ANSP); D. Werneke (AUM); D. Catania, Stuart
Willis (CAS); L. Fernanda, H. Agudelo (CIUA);J. G. Albornoz-Garzón, C.Conde, L. García-Melo, F. Villa-
Navarro (CZUT-IC); S. Mochel, K. Swagel, M. A. Rogers, P. Willink, and M. Littmann (FMNH); J. Maldonado-
Ocampo, J. Bogotá-Gregory, C. doNascimiento (IAvH); J. Mojica, H. Agudelo, Germán Galvis and Gustavo Ballen
(ICN-MHN); A. Ortega-Lara (INCIVA); A. Machado-Allison, F. Provenzano Rizzi, MBUCV; K. Marchetto, L.
Martínez, C. Marrero and O. Castillo, MCNG; K. Hartel (MCZ); C. Lasso, O. Lasso-Alcalá, MHNLS; J.
Maldonado, S. Prada-Pedreros and A. Urbano-Bonilla (MPUJ); Douglas Rodríguez-Olarte (UCLA); L. Page and
G. Sheehy (UF); J.Williams, R. Vari (USNM); Priya Majaraj, Devya Hemraj, Mark Ram, Elford Liverpool, Calvin
Bernard (CSBD). Special thanks to Saulo Usma and his family for their hospitality to DCT during his visits to
Colombia and to Elford Liverpool and Louisa Daggers for their hospitality in Guyana. Invitations to review and
identify fish specimens from Saulo Usma at WWF-Colombia, Carlos Lasso at the Instituto Alexander von
Humboldt and César Román-Valencia provided many opportunities to review material of Ancistrus in several
Colombian collections. We thank Nathan Lujan, Mark Sabaj and Alexander Urbano-Bonilla for live photographs.
INAPESCA kindly provided the scientific collecting permits for collecting in Venezuela, and the EPA for Guyana.
We thank the FMNH T. Lumbsch, A. Rosenthal, C. Vriesendorp and N. Pitman for funding and support to finalize
this study. This is Contribution No. 886 of the Auburn University Museum of Natural History.
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... Its dynamic and complex paleogeographic history has contributed to the tremendous biodiversity, spectacular table-top mountains called tepuis and remarkable waterfalls often cascading 500 m or more off the face of escarpments throughout the Shield (i.e., Angel Falls, Kaieteur Falls, Yutajé Falls). High levels of endemism are characteristic for the region particularly among several taxonomic groups (including cichlids, gymnotiform knifefishes, and siluriform catfishes) in the Guiana Shield with percentages as high as 80-95% (GAHEF, 1992;Duellman, 1999;Lopez-Fernandez et al., 2012;Maldonado Ocampo et al., 2013;Potapov et al., 2017;de Souza et al., 2019;Paz et al., 2019). Intriguing explorers for centuries, these highland regions of the Guiana Shield continue to remain poorly known due to remoteness and isolation. ..