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Description of a new species of the genus Chaetostoma from the Orinoco drainage with comments on Chaetostoma milesi Fowler (Siluriformes: Loricariidae)

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Chaetostoma joropo n. sp. is described from the piedmont of the Orinoco River drainage in Colombia. The new species has been long confused with Chaetostoma milesi, a species with similar overall morphology and color pattern that is restricted to the Magdalena-Cauca River Basin. We diagnose the new species on the basis of morphology as well as a precise description of the color pattern. Chaetostoma joropo n. sp. is also easily distinguished from C. formosae the most similar species and other species inhabiting the Orinoco River drainage in Colombia. Data on ontogenetic variation and sexual dimorphism are provided, as well as natural history notes and remarks on the usage of the name Chaetostoma milesi for specimens from both the Orinoco and Magdalena-Cauca drainages. A discussion on the usage of the name Chaetostoma platyrhynchus is also provided given its current instability in the literature.
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Accepted by M.R. de Carvalho: 15 Mar. 2016; published: 20 Apr. 2016
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http://doi.org/10.11646/zootaxa.4105.2.6
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Description of a new species of the genus Chaetostoma from the Orinoco River
drainage with comments on Chaetostoma milesi Fowler, 1941
(Siluriformes: Loricariidae)
GUSTAVO A. BALLEN
1,2,3
, ALEXANDER URBANO-BONILLA
3,4
& JAVIER A. MALDONADO-OCAMPO
3,5
1
Museu de Zoologia da Universidade de São Paulo, São Paulo, SP, Brazil. E-mail: gaballench@gmail.com; gaballench@usp.br
2
Center for Tropical Paleoecology and Archaeology, Smithsonian Tropical Research Institute, Ancón, Panamá.
3
Laboratorio de Ictiología, Departamento de Biología, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá, Colombia.
4
Instituto de Investigación de Recursos Biológicos Alexander von Humboldt. Bogotá, Colombia. E-mail: bio.ictiologia@gmail.com
5
Unidad de Ecología y Sistemática (UNESIS) Departamento de Biología, Facultad de Ciencias, Pontificia Universidad Javeriana,
Bogotá, Colombia. E-mail: maldonadoj@javeriana.edu.co
Abstract
Chaetostoma joropo n. sp. is described from the piedmont of the Orinoco River drainage in Colombia. The new species
has been long confused with Chaetostoma milesi, a species with similar overall morphology and color pattern that is re-
stricted to the Magdalena-Cauca River Basin. We diagnose the new species on the basis of morphology as well as a precise
description of the color pattern. Chaetostoma joropo n. sp. is also easily distinguished from C. formosae the most similar
species and other species inhabiting the Orinoco River drainage in Colombia. Data on ontogenetic variation and sexual
dimorphism are provided, as well as natural history notes and remarks on the usage of the name Chaetostoma milesi for
specimens from both the Orinoco and Magdalena-Cauca drainages. A discussion on the usage of the name Chaetostoma
platyrhynchus is also provided given its current instability in the literature.
Key words: Ancistrini, taxonomy, Hemiancistrus platyrhynchus, Andes, northern South America
Resumen
Se describe Chaetostoma joropo n. sp. del piedemonte de la Orinoquía en Colombia. Esta nueva especie ha sido confun-
dida por un largo tiempo con Chaetostoma milesi, una especie restringida al drenaje del Magdalena-Cauca a la que se ase-
meja en morfología general así como en patrón de coloración. Se diagnostica esta nueva especie con base en caracteres
morfológicos así como en base a una descripción más detallada del patrón de coloración. Chaetostoma joropo n. sp. es
fácilmente distinguible de otras especies presentes en el drenaje del río Orinoco en Colombia, de las cuales Chaetostoma
formosae es la especie más similar. Se presentan datos sobre variación ontogenética y dimorfismo sexual, así como notas
de historia natural y anotaciones sobre el uso del nombre Chaetostoma milesi para especímenes en los drenajes Orinoco
y Magdalena-Cauca. Se proporciona una discusión sobre el uso del nombre Chaetostoma platyrhynchus dada su inesta-
bilidad en la literatura.
Palabras clave: Ancistrini, taxonomía, Hemiancistrus platyrhynchus, Andes, Norte de Suramérica
Introduction
The genus Chaetostoma Tschudi currently comprises 47 species (Lujan et al. 2015a) distributed along the Andes
Mountains and Guyana Shield. This speciose genus is the second largest of the Ancistrini (sensu Lujan &
Armbruster 2011), a hypostomine tribe with an astonishing morphological, functional, and ecological diversity
(Lujan & Armbruster 2012). Along with being the second richest genus in the tribe, the incompleteness of
taxonomic research has left it as one of the most difficult groups of ancistrins (Armbruster 2004, 2008; Lujan &
Armbruster 2012).
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Most species of Chaetostoma were described before 1950, with just a few scattered works adding one or a
couple new species, but with very restricted comparisons with other species of the genus, and some even lacking a
diagnosis. In addition, a revisionary study on the taxonomy of Chaetostoma is still lacking and only one informal
subgeneric species group (the Chaetostoma anale species group, Ballen, 2011) has been recognized. Simultaneous
advances of both species description and internal organization (even phenetic efforts) of the genus are needed
before a phylogenetic hypothesis of relationships can be proposed, especially given that the validity of most
nominal species in Chaetostoma has not been revisited.
So far in Colombia the genus Chaetostoma includes 21 species (Chaetostoma anale, C. brevilabiatum, C.
dorsale, C. dupouii, C. fischeri, C. floridablancaensis, C. formosae, C. lepturum, C. leucomelas, C. marginatum, C.
milesi, C. niveum, C. nudirostre, C. palmeri, C. patiae, C. paucispinis, C. platyrhynchus, C. sovichthys, C.
tachiraense, C. thomsoni, and C. vagum) with distributions associated with Andean piedmont systems. Six of these
species are present in cis-Andean (east of the Andes) areas, whereas the remaining species are found in trans-
Andean (west of the Andes) river systems including the Maracaibo, Magdalena-Cauca, Atrato and Pacific Coast
systems such as the Patia basin (Ballen 2011; Maldonado-Ocampo et al. 2008).
The main goal of this work is to describe a new species from the Orinoco River Basin in Colombia long
referred to as C. milesi Fowler, 1941, while clarifying the taxonomic circumscription and geographic range of the
latter species in Colombia. This increases to four the formally described Chaetostoma species known from the
Colombian Orinoco River Basin, leaving only one more known undescribed species among the material available
in museum collections.
Materials and methods
Counts and measurements follow (Armbruster 2003) except for the inclusion of the second anal-fin ray length, not
measured in the referred work; morphometric variable names are used in abbreviated form throughout the text.
Measurements from the tip of snout were taken from the tip of the mesethmoid because species of Chaetostoma
present extensive development of the skin and adipose tissue underneath the epidermis, therefore affecting
repeatable measurements from the unplated snout. Museum acronyms for material examined in this study follow
Sabaj-Pérez (2013). Material examined is reported using the following sequence: Catalog number, number of
specimens, SL range, locality, collector and date.
Abbreviations in the text are SL (standard length), HL (head length), c&s (cleared and stained specimens
prepared following the method of Taylor & van Dyke 1985), and NSA (northern South America). Osteological
nomenclature follows Geerinckx & Adriaens (2006) and Geerinckx et al. (2007) with exception of “cheek spines”,
called instead “cheek odontodes” herein in order to be consistent with the histology of these structures. Position of
fleshy ridges on pelvic- and anal-fin rays are reported following the insertion plane of the fin; for instance, pelvic
fins show dorsal and ventral planes, whereas anal fin shows anterior and posterior planes. Terminology of lateral
plate series follows Schaefer (1997). The fleshy parieto-supraoccipital keel has received in literature at least two
names: Fleshy excrescence (Salcedo 2006a, b), and parieto-supraoccipital keel (Ballen 2011); we standardize here
the term as parieto-supraoccipital excrescence since the term keel has been widely used for bony structures
associated with lateral plate series or medial bony structures on the parieto-supraoccipital in loricariids of several
hypostomine genera and therefore the term excrescence would resolve potential ambiguities.
Statistics were performed with the program R v. 3.1.1 (R Core Development Team 2012) and the RStudio GUI
v. 0.98.1028, available at http://www.r-project.org/ and http://www.rstudio.com/ respectively. In addition the
packages dplyr, extremevalues, factoextra, FactoMineR, npsm, randtests, Rfit and xlsx were used (Caeiro &
Mateus 2014; Dragulescu 2014; Husson et al. 2015; Kassambara 2015; Kloke & McKean 2012, 2014; van der Loo
2010; Wickham & François 2015). The statistical approach was first to carry out a variable reduction with the aid
of a PCA following Jolliffe (2002) and Todeschini & Consonni (2008) in order to select those variables that explain
most of the variation in the dataset, and then to test for normality and randomness for each single variable with the
Shapiro-Wilk and the Bartels tests respectively. Since non-normality was detected for some variables, and given
the nature of ratio data (Curran-Everett 2013), we used a non-parametric robust ANCOVA (Hettmansperger &
McKean 2010; Kloke & Mckean 2014) in order to find variables that explain differences in shape between the new
species and C. milesi. The statistical analyses show that from the original 35 variables proposed by Armbruster
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(2003), 12 in our dataset explained more than 80% of the variation and were selected for inferential analysis. These
were further reduced to nine (Head-dorsal L., Head-eye L., Dorsal-pectoral D., Dorsal-spine L., Dorsal-pelvic D.,
Caudal peduncle Dp., Pelvic-dorsal D., Mouth L., and Mouth W.) after excluding those that violated the
assumption of randomness based on the results of the Bartels test.
The code and raw data used in the data analysis are both available along with further comments in the first
author's GitHub repository at https://github.com/gaballench/Cjoropo.
Chaetostoma joropo, new species
(Fig. 1, Table 1)
Chaetostoma milesi (non Fowler, 1941)(Lasso et al. 2004; Maldonado-Ocampo et al. 2008, 2013; Ortega-Lara et al. 2011;
Urbano-Bonilla et al. 2009, 2014) [In checklists].—Zamudio et al. (2008) [Trophic ecology].—(Rodríguez-Olarte et al.
2011) [Basin-scale records within biogeographic analysis including C. milesi as present in both Magdalena-Cauca and
Orinoco drainages]
Holotype. MPUJ 7197, male, 108.8 mm SL, Colombia, Meta, Mesetas, Resevera, Guaviare, río Güejar, upper río
Guaviare basin, Orinoco River Basin, coll. J. A. Maldonado-Ocampo et al., 8-Dec-2013.
Paratypes. All from Colombia. ICNMHN 1795, 13, 60.8 – 105.6 mm SL, Meta, La Macarena, río Güejar, no
coordinates available, coll. F. Jiménez-Segura et al., 1-Jan-1992; MPUJ 7198, 34, 85.7 – 31.0 mm SL, collected
with the holotype; MPUJ 7201, 3, 82.4–99.6 mm SL, Casanare, Tauramena, Meta, río Cusiana, 5°00'0.13"N,
72°40'0.5"W, coll. S. Prada-Pedreros, 6-Jul-2014; MPUJ 7202, 5, 25.0 – 97.8 mm LS, Casanare, Tauramena, Meta,
río Cusiana, 5° 01'21.7"N, 72°41'27.8"W, coll. S. Prada-Pedreros, 29-Sep-2012; MPUJ 7203, 19, 31.0–124.7 mm
LS, same collector and locality data as MPUJ 7201, 11-Dec-2012; MPUJ 7204, 32, 12.5–90 mm SL, same collector
and locality data as MPUJ 7201, 11-Feb-2013; MPUJ 7205, 182, 15 – 97.2 mm SL, same collector and locality data
as MPUJ 7202, 10-Feb-2013; MPUJ 7206, 13, 37.0–72.8 mm SL, Casanare, Tauramena, Meta, río Caja,
5°10'11.8"N, 72°42'17.9"W, coll. S. Prada-Pedreros, 8-Feb-2013.
Non-type specimens. MPUJ 7199, 37, 72.7–27.6 mm SL, Meta, Vista Hermosa, Vereda Puerto Lucas, río
Güejar, 3°1'37.35"N, 73°50'24.70"W, coll. J. A. Maldonado-Ocampo, 7-Dec-2013; MPUJ 7200, 1, 36.1 mm SL,
Meta, Vista Hermosa, Caserío Maracaibo, Guaviare, Quebrada Sardinata, 3°20'39.91"N, 73°20'39.91"W, coll. J. A.
Maldonado-Ocampo, 7-Dec-2013; MPUJ 7305, 2, 82.1–86.2 mm Sl, Arauca, Tame, Vereda el Banco Purare, río
Purare, 6°15'51"N, 71°51'38.8"W, coll. J. Zamudio, 9-May-2015; MPUJ 7306, 1, 92.8 SL mm, Arauca, Tame,
Vereda el Banco Purare, río Tocoragua, 6°16'52"N, 71°52'23.7"W, coll. J. Zamudio, 9-May-2015.
Diagnosis. Chaetostoma joropo differs from all the species currently known to be present in the Orinoco River
Basin by having dark spots on head and body as well as on dorsal, pectoral and pelvic fins (vs. dark spots present
only on head in Chaetostoma formosae, light dots on head in C. dorsale and C. platyrhynchus, dark spots absent in
C. vasquezi). It also differs as follows: from Chaetostoma formosae in the absence of sexual dimorphism in the
length of the second unbranched ray of the anal fin (vs. dimorphism present); from Chaetostoma dorsale and C.
platyrhynchus by the presence of recurved cheek odontodes and a parieto-supraoccipital excrescence (vs. cheek
odontodes straight and excrescence absent), and from Chaetostoma platyrhynchus in having a naked snout (vs.
snout covered with plates).
Only a few species of Chaetostoma present a color pattern consisting of spots on both the head and the body
(C. anale, C. daidalmatos, C. lineopunctatum, C. milesi, C. strompoulos, C. trimaculineum and C. vagum, (Lujan et
al. 2015a; Salcedo 2006b). Chaetostoma joropo differs from these species except C. daidalmatos by having spots
on the body that are larger (in diameter) than the spaces separating them from neighboring spots(vs. space between
spots larger or equal to spot diameter in C. anale, C. lineopunctatum, C. milesi, C. strompoulos, and C. vagum).
Chaetostoma joropo differs from C. daidalmatos by having spots that are smaller than the orbital diameter (vs.
spots larger than orbital diameter, (Salcedo 2006b). Finally, Chaetostoma joropo differs from C. milesi as follows:
by having the spots on the head more densely packed together, with the space between spots smaller than spot
diameter (vs. spots less numerous and with space between spots larger than spot diameter in C. milesi); by having
more spots on body that are better organized in longitudinal rows (vs. spots less numerous and scattered in C.
milesi
); by the presence of scattered, numerous spots on the dorsal fin (vs. less numerous and always positioned
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anterior to each branched fin ray in C. milesi); by having a uniform black coloration on the dorsal surface of the
pectoral spine (vs. with longitudinal row of spots on dorsal surface of pectoral spine in C. milesi); and by
presenting undulated vertical bars on the caudal fin that transform progressively into spots (vs. caudal fin uniformly
dark regardless of size in C. milesi).
Description. Measurements presented in Table 1. A large-sized Chaetostoma, with largest examined specimen
124.7 mm SL (paratype male, MPUJ 7203). Head and body slightly depressed and wide. Dorsal profile of anterior
portion of head in lateral view convex from unplated region of snout to vertical through posterior nares, then
convex toward dorsal-fin insertion. Dorsal profile of body straight to slightly convex and concave from dorsal-fin
insertion to caudal-fin origin. Ventral profile of head and body straight from snout tip to caudal peduncle.
Interorbital area slightly convex. Dorsal surface of snout region convex. Head in dorsal view roundish or oval
with irregular margin due to development of skin. Snout naked, covered by fleshy papillae and ridges. Anterior
margin of plated portion of snout roughly V- or U-shaped, starting on snout midline and then extending posteriorly
to dorsal margin of exposed portion of opercle forming ventral margin nearly parallel or slightly oblique to ventral
head margin. Unplated snout region more extensive in mature males than in females. Parieto-supraoccipital dermal
excrescence present.
All lateral plate series other than ventral series complete from compound pterotic to caudal peduncle; ventral
series incomplete anteriorly and beginning anterior to pelvic-fin insertion. Abdomen completely naked. First anal-
fin pterygiophore not exposed. Median series with 23–25 plates (mode 24), showing individual and intraindividual
variation.
Hypertrophied cheek odontodes distally and strongly recurved, usually not surpassing posterior margin of
exposed opercle when adpressed. Exposed portion of opercle roughly triangular in shape, weak mesial indentation
evident externally where musculus dilatator operculi complex inserts onto opercle. Cheek plates not exposed.
Fleshy ridge posterior to cheek odontodes present, sometimes reaching ventral margin of exposed opercle dorsally
when cheek odontodes adpressed. Frontal, infraorbital, nasal, exposed opercle, compound pterotic, sphenotic, and
parieto-supraoccipital bones supporting odontodes. Odontodes present on exposed portion of opercle.
Odontodes flat and sharp on lateral plates but flat and spatulate on area between orbit and naris, mesethmoidal
region and dorsal surface of snout. Odontodes flat and spatulate on dorsal surface of dorsal spine and spinelet,
adipose fin, and dorsal leading ray of caudal fin. Odontodes flat and spatulate on ventral and lateral surfaces of
pectoral and pelvic fin, and on anterior surface of anal fin and ventral leading ray of caudal fin. Hypertrophied
pectoral-spine odontodes basally surrounded by fleshy collar and frequently with small posterior papilla.
Remaining odontodes developing directly on plates and rays without associated papillary soft tissues. All plates of
lateral series with largest odontodes on posterior margin and shorter ones on plate surface.
Posterior tip of dorsal-fin reaching or surpassing origin of adipose spine when adpressed. Dorsal spine not
elongate or extending beyond margin of remainder of fin. Dorsal spine stiff basally but flexible distally. Distal
margin of dorsal fin slightly convex. Margin of dorsal-fin spinelet moderately acute, bearing odontodes. Dorsal-fin
spinelet exposed in mature specimens, regardless of sexual condition. Dorsal-fin lock functional. Dorsal-fin ray
formula ii,8. Adipose spine preceded by one unpaired plate. Dorsal procurrent caudal-fin rays 5–6 (mode 5) and
ventral procurrent rays 4–5 (mode 4). Caudal fin oblique with lower portion longer than upper portion; dorsal and
ventral unbranched rays longer than branched rays; distal margin emarginate. Caudal-fin base covered by acute
platelets variable in number. Caudal-fin ray formula i,14,i (i,13,i in one individual). Anal-fin base short. Anal-fin
ray formula ii,3–4 (mode ii,4). Pectoral spine with short and thick hypertrophied odontodes on tip but with distinct
dorsal row of odontodes throughout midline, showing sexual variation in odontode curvature. Tip of pectoral spine
when adpressed reaching to level of vent in mature specimens. Posterior margin of pectoral fin straight to slightly
convex. Tip of adpressed pectoral spine reaching from one-third to middle of leading pelvic-fin ray length.
Pectoral-fin ray formula i,6. Tip of pectoral spine when adpressed reaching or sometimes surpassing level of vent
in mature specimens. Odontodes on dorsal surface of pelvic-fin rays not hypertrophied and not protruding from
skin in both males and females. Pelvic fin with variable distal margin from convex and round in females to strongly
convex and angular in mature males. Pelvic-fin leading ray more than twice as thick as remaining rays. Pelvic-fin
ray formula i,5.
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TABLE 1. Measurements for Chaetostoma joropo n. sp. Landmarks and measurements follow Armbruster (2003)
except for Anal-fin second ray L., not measured in that work. Predorsal L. through Pelvic-dorsal D. are percentages of
SL; Head-eye L. through Premax.tooth. cup L are percentages of Head L. Standard Deviation = SD.
Chaetostoma joropo n. sp. Chaetostoma milesi
Measurement Mean SD Range Mean SD Range
SL 88.1 16.6 63.1–124.7 105.4 16.8 82.3–146.7
Predorsal L. 45.9 2.8 39.9–52.5 43.3 2.6 40.7–50.4
Head L. 36.1 2.2 31.8–41.7 34 3.5 31.7–46.3
Head-dorsal L. 10.3 1.4 8.7–15.4 9.9 0.9 8.3–11.5
Head-eye L. 28.6 1.3 26.1–31.1 31.4 2.3 25.2–34.2
Orbit Dia. 13.2 2.3 10.2–16.9 14.6 4.2 11.3–29.9
Snout L. 70.7 3.1 66.4–80.7 71.1 5.2 52.1–74.3
Internares W. 12.5 5.1 7.3–22.1 18.8 3.9 13.1–31.6
Interorbital W. 37.3 6.4 28–47.5 46.2 3.3 36–50.4
Cleithral W. 35.4 1.9 30.2–38.4 33.3 1.5 30.5–38.1
Head-pectoral L. 30.4 2.9 25–36 26.8 4.3 18.6–31.7
Thorax L. 22.3 1.9 18.2–25.4 22.5 1.2 20.3–24.8
Pectoral spine L. 31.2 2.1 26.8–35.2 30.9 1.5 28.6–33.9
Abdominal L. 24.6 1.7 21.1–28.9 23.8 2.9 21.3–31.8
Pelvic spine L. 26.5 1.8 23.1–30.9 25.7 1.4 24.2–29.6
Postanal L. 30.7 1.9 27.5–34.8 31.2 2 28.2–37
Anal fin spine L. 9.7 2.2 6.9–13.9 11.3 1.8 5.6–14.5
Head Dp. 76 3.8 69.8–88.2 70.3 5.2 52.2–74.9
Dorsal-pectoral D. 31.5 2.4 25.6–36.8 28 1.3 26.7–32.2
Dorsal spine L. 29.6 3.6 23.1–44.4 28.6 1.6 26.3–31.5
Dorsal-pelvic D. 25.5 1.6 22.7–29.6 23.2 1.6 20.7–27.5
Dorsal fin base L. 28.9 2.8 25.6–40.4 27.3 1.1 25.5–30
Dorsal-adipose D. 14 1.8 10.1–16.9 16.2 1.2 14.1–19.4
Adipose spine L. 9 0.7 7.9–10.9 8.9 0.5 8.3–9.9
Adipose-upper caudal D. 13.2 0.9 11.6–14.9 15.1 1.5 13–18.6
Caudal peduncle Dp. 14.1 1.5 11.2–17 12.9 0.8 11.5–14.3
Adipose-lower caudal D. 23.2 2 20.3–26.9 21.5 0.9 19.4–22.8
Adipose-anal D. 20.3 1.2 18.3–23.1 19.9 0.9 18.2–21.1
Dorsal-anal D. 31.4 2.2 27.2–37.6 28 1.8 25.3–32.3
Pelvic-dorsal D. 31.4 2.2 27.2–37.6 28 1.8 25.3–32.3
Mouth L. 61.3 4.8 52.5–75.3 59.9 4.9 44–67.5
Mouth W. 92 6.1 83–109.8 85.9 7 62.6–95.1
Barbel L. 12.1 1.7 9.3–16.1 11.4 8.2 6.6–41.7
Dentary tooth cup L. 36.1 3.3 30.2–44.1 32.5 3.1 23.8–36.9
Premaxillary tooth cup L. 31.1 3 27.4–38.6 27.6 2.6 19.9–30.5
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FIGURE 1. Chaetostoma joropo n. sp., holotype, MPUJ 7197, 108.8 mm SL, dorsal, lateral, and ventral views. Scale bar
equals 1 cm. Photographs by J. E. García-Melo.
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FIGURE 2. Chaetostoma joropo n. sp., coloration in life from the río Güejar, Meta, Colombia. Specimens not preserved.
Photographs by O. Lucanus.
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FIGURE 3. Ontogenetic variation in color pattern in Chaetostoma joropo n. sp. (left, MPUJ 7199) and Chaetostoma milesi
(right, CZUT-IC 10593). Juveniles below, subadults in middle row, adults above. Scale bar equals 1 cm. Photographs by A.
Urbano-Bonilla.
Iris operculum present. Short, fleshy flap with round margin present between anterior and posterior nares,
deeper mesially. Upper lip with multiple series of papillae, those proximate to mouth opening small and round,
followed distally by larger and widely elongate ones. Lower lip with medium-sized round papillae anteriorly and
smaller ones posteriorly, with smooth skin close to posterior margin of lip; border crenate. Maxillary barbels
moderate in length, separate distally from lower lip. Lower lip basally fused up to one-third or even half of total
barbel length in some individuals; fleshy ridge present dorsally almost over entire length of each barbel, also
showing individual variation. Buccal papilla present at symphysis of premaxillae. Premaxillary ornamentation
usually consisting of individual small papillae arranged transversely. Dentary ornamentation consisting of mesial
transverse papillary ridge and secondary single papillae arranged lateral to main ridge.
Jaws wide transversely. Posterior margin of premaxillae forming nearly straight line. Dentary wider than
premaxilla. Both rami with nearly straight tooth cups only recurved on lateral margins. Tooth peduncle fairly long,
narrow, and distally recurved. Cusps asymmetrically developed with lateral tooth cusp approximately one-half
length of medial cusp. Dentary teeth 32–157, premaxillary teeth 24–128, showing increase with age.
Coloration in alcohol. Overall body background grayish-green with black spots on head, fins and body. Head
and dorsum with scattered black spots; lateral plates with dense and numerous dark spots, tending to become
aligned in longitudinal rows posteriorly. Parieto-supraoccipital fleshy excrescence usually black, but sometimes
less intensely pigmented. Pectoral, pelvic, dorsal, anal, and caudal fins with dusky membranes and scattered
numerous spots. Pectoral spine with black pigment. Dorsal fin with basal anterior black spot between leading ray
and first branched ray absent in contrast to presence in C. formosae. Anal fin with dark blotches, ill-defined and
very few in number. Caudal fin with undulated bars on caudal fin that transform progressively into spots with age.
Venter light, without dark pigment.
Coloration in life. Specimens of Chaetostoma joropo show variation in color pattern ranging from yellowish-
green background coloration to grayish green; venter and preanal regions are in both cases lighter, and darker
posterior to anal fin. Pattern also includes back spots on head, fins, dorsum and sides of body, in contrast to ventral
portions other than on caudal peduncle that lack spots, with just few spots on postanal region. Interradial
membranes share the same color as background pattern. Adults with longitudinal black stripe on pectoral spine
extending from base to tip; in juveniles stripe proximally interrupted and consisting of spots (Figure 2).
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Ontogenetic variation. Chaetostoma joropo shows ontogenetic variation in color pattern and development of
pelvic-fin distal margin. Juveniles present an almost plain color pattern with few large blotches that become
progressively smaller until transformation into more numerous spots better organized in rows (Figure 3). Both male
and female juveniles have a more narrow naked area on snout that becomes wider in adults, further showing sexual
dimorphism between males and females. Supraoccipital excrescence more pronounced in juveniles than adults,
probably as a consequence of thickening of dorsal skin in adults. Distal margin of pelvic fin in juveniles straight,
becoming round in adults as observed in other species of Chaetostoma (e.g., C. milesi).
Sexual variation. Mature males develop a fleshy dorsal ridge on the pelvic-fin leading ray, from insertion
of fin to near the tip of ray; in contrast, females lack such condition. Mature males show a more extensive unplated
portion of snout, whereas mature females show a more plated snout. Dorsal longitudinal single row presents acute
recurved odontodes in mature males whereas mature females show more straight odontodes. Distal margin of
pelvic fin convex and round in both sexes, but males usually have more developed pelvic fins than females. Males
have a pointed and discrete genital papilla, that in females is a wide and pad-like papilla. The papillae in both sexes
have a terminal aperture; however, once reaching maturity and when eggs are mature, females develop a swollen
posterior portion, which makes the papilla appear to be directed towards the vent tube. Males are larger than
females (largest male examined 124.7 mm SL vs. largest female examined 115.1 mm SL, both mature adults).
Distribution. Chaetostoma joropo is present in piedmont rivers of the Orinoco River Basin in Colombia.
Based on voucher specimens we record its presence in the Casanare, Meta and Guaviare drainages, from Vista
Hermosa in the Departamento de Meta to the south to the río Tocoragua in the municipality of Tame, Departamento
de Arauca to the north (Figure 4). The distribution of this species coincides with that of C. dorsale, C. formosae
and Dolichancistrus fuesslii in the Orinoco drainage (Ballen & Vari 2012; Ballen 2011).
FIGURE 4. Distribution map of Chaetostoma joropo n. sp. (triangles) and Chaetostoma milesi (circles) in cis- and trans-
Andean Colombia, respectively. Type localities are indicated by numbers for both C. joropo (1) and C. milesi (2).
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Ecological notes. Chaetostoma joropo shows preference for rocky substrates, shallow (0.20–0.55 m) but well
oxygenated water (6.1–9.5 mg/L), and slightly basic pH (7.1–8.6); conductivity (10.4258.0 µS) as well as
temperature (21–30°C) are variable (Figure 5). This species occasionally feeds on insect larvae (Diptera), and are
mostly algivores (e.g., Aulacoseira sp., Cymbella sp., Fragilaria sp., Gyrosigma sp., Navicula sp., Oscillatoria sp.,
Pinnularia sp., Surirella sp., Spirogyra sp., Synedra sp., Tabellaria sp.). Chaetostoma joropo occurs with other
species of the same family (Chaetostoma dorsale, C. formosae, C. platyrhynchus, Panaqolus maccus and
Lasiancistrus tentaculatus) as well as crenuchids (Characidium gr. boavistae, C. chupa and C. cf. steindachneri),
parodontids (Parodon apolinari), characids (Bryconamericus cismontanus, B. cristiani, Creagrutus bolivari, C.
taphorni, C. maculosus, Hemibrycon metae and Salminus hilarii), heptapterids (Cetopsorhamdia orinoco,
Phenacorhamdia macarenensis and Rhamdia quelen), cetopsids (Cetopsis orinoco and C. coecutiens), aspredinids
(Hoplomyzon sexpapilostoma), trichomycterids (Trichomycterus knerii, Ochmacanthus alternus, Schultzichthys
bondi and S. gracilis), apteronotids (Apteronotus albifrons), and cichlids (Crenicichla saxatilis).
Etymology. The word joropo refers to a collection of musical styles that originated in the Llanos region of the
Orinoco River Basin. It is one of the most characteristic cultural expressions among the criollos, the people who
live in the Llanos Orientales. This name recognizes the importance and beauty of this region through one of its
most iconic cultural expressions, which does not account for political boundaries and promotes brotherhood among
the people of Colombia and Venezuela. It is used as a noun in apposition.
Discussion
Zoogeography of the genus Chaetostoma in cis-Andean NSA. Historically several species names have been
applied to cis-Andean Chaetostoma inhabiting NSA. For instance, Lasso et al. (2004) recorded C. dorsale, C.
milesi and C. vasquezi for the whole Orinoco River Basin of Colombia and Venezuela, while Maldonado-Ocampo
et al. (2008) extended the records to C. dorsale, C. dupouii, C. milesi and C. nudirostre for the Orinoco River
Basin, and C. anale and C. vagum for the Amazon River Basin in Colombia. Armbruster (2004) reassigned
Hemiancistrus platyrhynchus Fowler from Cordylancistrus to Chaetostoma based on phylogenetic evidence, thus
raising to five the number of species present in the Amazon River Basin of NSA (including C. jegui; Rapp Py-
Daniel 1991). Ballen (2011) later described C. formosae from the Colombian Orinoco River Basin, raising the
number to six.
It is noteworthy that despite the fact that the type localities of C. dupouii (río Tuy drainage) and C. nudirostre
(Lago Valencia drainage) lay outside the Orinoco River Basin, and that museum records in Venezuelan collections
do not include localities in the Orinoco River Basin (based on the records published in Lasso et al. 2004), such
records have been published for Colombia. Examination of specimens in Colombian collections identified as
Venezuelan species such as C. sovichthys, C. dupouii and C. anomalum from the Colombian Orinoco River Basin
were misidentifications of Chaetostoma dorsale, a very common species in the area similar to the former ones
mentioned in lacking a parieto-supraoccipital excrescence and in having straight cheek odontodes. Neither among
the material examined in Ballen & Vari (2012) and Ballen (2011) nor the additional specimens herein studied was
found a single record of a species with straight cheek odontodes other than C. dorsale and C. platyrhynchus. We
consequently suggest the exclusion of C. anomalum, C. dupouii and C. sovichthys from the species considered as
present in the Orinoco River Basin until accurately-identified specimens of those species become available. Thus,
the only species present so far in the Orinoco River Basin are C. dorsale, C. formosae, C. joropo, C. platyrhynchus
[new record] and C. vasquezi.
The case for the Amazonian species is more complicated given the uncertainty about the validity of C. vagum,
which seems to be a synonym of C. anale (G. A. Ballen, pers. obs.); however, we still recognize C. anale, C. jegui,
C. platyrhynchus and C. vagum in the Amazon River Basin of NSA. Assuming that all the five species of
Chaetostoma from the Amazonian River Basin in NSA are valid, all but one would be restricted to that basin given
that C. platyrhynchus is also present in the southernmost portion of the Orinoco River Basin Andean piedmont.
Therefore, both the Amazon and Orinoco basins would share only one out of five species for each drainage
respectively. Unfortunately the Amazon piedmont still remains largely unexplored in Colombia based on museum
records, so an accurate extent of distribution patterns is to date impossible to ascertain. Nevertheless the differences
in terms of species present in both drainages is noteworthy and will require extensive collections in the Andean
versant of the Amazon River Basin as well as phylogenetic studies that will allow us to understand the historic
component underlying the differential composition in the genus Chaetostoma east of the Andes.
Morphometrics: How do C. joropo and C. milesi differ from each other? The robust ANCOVA showed that
five of the variables that showed significant differences between C. joropo and C. milesi also showed homogeneous
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slopes and therefore SL did not affect their behavior as a covariate. An additional variable showed heterogeneous
slopes and significant differences, suggesting that SL as a covariate had a differential effect for each species.
Finally, for three variables there were non-significant differences between species, suggesting that they do not
differ in terms of such variables (Table 2, Figures 6, 7).
FIGURE 5. Habitat of Chaetostoma joropo n. sp. in the Serranía de La Macarena. Photograph by A. Urbano-Bonilla.
TABLE 2. Robust ANCOVA table for a reduced subset of morphometric variables in Chaetostoma joropo n. sp. and
Chaetostoma milesi. P-values with the "<<" symbol were more than two orders of magnitude smaller than 0.001.
For Dorsal-pectoral L., Pelvic-dorsal D., Caudal peduncle Dp., and Mouth W., C. joropo had higher values that
significantly differed from those of C. milesi, while for Head-eye L. the latter species had higher values (Figure 4).
Variable p-value F-value Homogeneity of slopes
Head-dorsal L. 0.3512 0.8899 Homogeneous
Dorsal-pectoral D. << 0.001 24.5744 Homogeneous
Dorsal spine L. 0.1459 2.1996 Homogeneous
Dorsal-pelvic D. 0.0103 7.2682 Heterogeneous
Caudal peduncle Dp. 0.0345 4.7927 Homogeneous
Pelvic-dorsal D. << 0.001 41.2275 Homogeneous
Head-eye L. << 0.001 61.7052 Homogeneous
Mouth L. 0.8308 0.0463 Homogeneous
Mouth W. 0.0045 9.0817 Homogeneous
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The former set of variables indicates that C. joropo has a more robust body and a wider mouth than C. milesi. A
possible explanation is that at least two of the body measurements depend on the position and length of the dorsal
fin; however, predorsal length did not differ between species, which suggests that overall robustness or height is
responsible for the observed differences. This would be consistent with a deeper caudal peduncle in C. joropo than
in C. milesi. As for mouth width, an alternative would be to consider that overall C. joropo has a larger mouth than
C. milesi (Figure 5); however, this interpretation is rejected because mouth length did not differ between species
(Table 2). Finally, Dorsal-pelvic D. showed heterogeneous slopes and significant differences, which suggests that
SL has a differential effect for each species; as for the magnitude such variables had larger values in C. joropo than
in C. milesi, which agrees with other variables describing body robustness (Figures 4, 5).
FIGURE 6. Scatterplot and robust fit line for morphometric variables showing significant differences and homogeneous slopes
between Chaetostoma joropo n. sp. and Chaetostoma milesi against their respective covariate (either SL or HL).
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FIGURE 7. Scatterplot and robust fit line for morphometric variables showing significant differences and either homogeneous
or heterogeneous slopes between Chaetostoma joropo n. sp. and Chaetostoma milesi against their respective covariate (either
SL or HL).
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Despite such differences we refrain from using measurements as diagnostic given the fact that their ranges do
show some overlap, and therefore restrict their relevance to overall differences in shape that await further study and
explanation. We found that many of the 35 morphometric variables proposed by Armbruster (2003) are redundant
when investigating shape differences between species of Chaetostoma, which suggests that this should be reviewed
in other studies using morphometric variables as diagnostic characters for other hypostomine genera. We favor an
approach that analyzes morphometric variables after carrying out a variable reduction procedure, to isolate noise
from uninformative or redundant variables.
The correct spelling of Hemiancistrus platyrhynchus Fowler. Hemiancistrus platyrhynchus Fowler, 1943 is
a species described from the Andean foothills of the upper Caquetá River basin in Colombia. It remained in its
original genus until its relocation to Peckoltia by Isbrücker (1980). The first time it was associated with a genus of
the Chaetostoma group was by Burgess & Finley (1996) following an unpublished meeting abstract by Provenzano
& Milani, who relocated it to Cordylancistrus without further comments. Isbrücker (2001) kept the species in the
latter genus, and after becoming a standard in loricariid classification the species was considered Cordylancistrus
platyrhynchus. Armbruster (2004) relocated it to Chaetostoma based on his strict-consensus tree where this species
is located at the base of the genus and in order to correct the non-monophyly of Cordylancistrus. The combination
Chaetostoma platyrhynchus has been quite stable in taxonomic literature regarding the Chaetostoma group except
for corrections in the spelling of the specific epithet. An ambiguity in the usage of the name platyrhynchus started
with Armbruster (2004) who used indistinctly the names Chaetostoma platyrhynchus and Chaetostoma
platyrhyncha for the same species in different sections of his article (e.g., pp. 45 and 72 for the former, and pp. 13,
34, 44 and 65 for the latter). Subsequently the same species was referred to as Chaetostoma platyrhynchus by the
same author in a reanalysis of the phylogenetic relationships of the Loricariidae (Armbruster 2008), an action
followed by Ballen & Vari (2012) and Ballen (2011). Finally, in the description of Cordylancistrus santarosensis,
Tan & Armbruster (2012) used the name Chaetostoma platyrhyncha consistently throughout their paper,
maintaining a dual usage of specific names for the same biological entity.
The fourth edition of the International Code of Zoological Nomenclature indicates that the gender in specific
epithet must fit that of the genus except in very precise cases (Art. 34). It seems that the change in spelling
introduced by Armbruster (2004) and followed by Tan & Armbruster (2012) was thought to follow this general rule
of agreement in gender between genus and species (Art. 31.2); however, that being the case the combination should
have been platyrhynchum (neuter) and not platyrhyncha (feminine), since Chaetostoma is neuter in gender.
However, even gender coordination does not apply here following Art. 31.2.1 since platyrhynchus is a compound
noun (from platys and rhynchos, both greek but latinized by Fowler as platyrhynchus in accordance with the
original genus Hemiancistrus being masculine), and therefore it is to be treated as a noun in apposition with
unchanged ending. Therefore, regardless of the generic combination (i.e., Chaetostoma or Cordylancistrus), its
ending must be preserved from the original usage, and therefore the name has to be used as Chaetostoma
platyrhynchus (Fowler).
Key to the species of Chaetostoma from the Orinoco River Basin in Colombia
Photographs illustrating the characters of interest in the present key are available along with dorsal, lateral and
ventral overall views for each of the species found in the Colombian Orinoco drainage, as well as additional
materials are available at https://github.com/gaballench/Cjoropo.
1a. Cheek odontodes straight; parieto-supraoccipital excrescence absent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1b. Cheek odontodes curved, parieto-supraoccipital excrescence present . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2a. Snout covered with plates; light spots present on head. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chaetostoma platyrhynchus
2b. Snout naked; light spots sometimes present on head, body, pectoral and pelvic fins, dorsal fin always with light spots . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chaetostoma dorsale
3a. Spots present only on head and area surrounding dorsal-fin base; dorsal, pectoral, pelvic and anal fins with dark bands; sexual
dimorphism in the anal fin where males have the second unbranched anal-fin ray elongated . . . . . . . . Chaetostoma formosae
3b. Spots present on head and body; dorsal, pectoral, pelvic and anal fins with spots, sexual dimorphism in the anal fin absent . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Chaetostoma joropo n. sp.
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Material examined
All the material examined in Ballen (2011) and Ballen & Vari (2012) was used in the present study. Herein we
present additional specimens examined that were not included in those studies.
Chaetostoma anomalum: MZUSP 2687, 1, 101.5 mm SL, Venezuela, Mérida. Chaetostoma jegui: All from
Brasil. MZUSP 41303, paratypes, 2, 73.9–123.1 mm SL, Roraima, rio Uraricoera, Ilha de Maracá; MZUSP 23603,
6, 44.8–129.4 mm SL, Roraima, rio Uraricoera, Ilha de Maracá, 3º28'00"N, 60º58'00"W. Chaetostoma
lineopunctatum: All from Perú. MZUSP 26737, 6, 54.4–74.0 mm SL, Ucayali, río Huacamayo, Pucallpa-Huánuco
road; MZUSP 106689, 3, 65.4–72.4 mm SL, Madre de Dios, río Loromayo 29.7 km ENE of Quincemil.
Chaetostoma milesi: All from Colombia. ANSP 69330, holotype, 1, 77.5 mm SL, Tolima, Honda; CZUT-IC 977 ,
10, 42.6–79.9 mm SL, Tolima, río Anchique, Resguardo Indígena el Guasimal, 3°34'35.0"N, 75°07'13.0"W;
CZUT-IC 1667 , 2, 40.3–64.3 mm SL, Tolima, Cunday, río Cunday, Parroquia Vieja, 4°01'58.0"N, 74°34'57.0"W;
CZUT-IC 1995 , 7, 26.0–71.3 mm SL, Tolima, Chaparral, Quebrada Guaini, Vereda Guaini, 3°40'19.0"N,
75°21'08.0"W; CZUT-IC 2218 , 10, 58.3–90.0 SL, Caldas, Norcasia, río La Miel, Vereda La Cuarenta, Puente de
hierro, vía Norcasia—Dorada, 5°34'27.0"N, 74°51'47.0"W; CZUT-IC 2251 , 1, 120.7 mm SL, Caldas, Samacá, río
Tasajos, Vereda Costa Rica, 5°23'32.0"N, 74°56'07.0"W; CZUT-IC 2434 , 10, 46.1–75.6 mm SL, Tolima,
Alvarado, río Alvarado, debajo del puente de la vía central, Vereda Ático Tamarindo, 4°31'03.0"N, 74°59'04.0"W;
CZUT-IC 3884 , 1, 77.4 mm SL, Tolima, Melgar, río Sumapaz, Vereda Las Palmas, 4°10'24.0"N 74°33'50.0"W;
CZUT-IC 3940 , 7, 72.1–100.1 mm SL, Tolima, Piedras, río Opia, El Platanal, 4°31'06.0"N 74°54'22.0"W; CZUT-
IC 5896 , 10, 53.4–92.1 mm LS, Tolima, Armero, río Sabajdija, Quebrada Santo Domingo, 5°00'13.0"N,
74°54'14.0"W; CZUT-IC 7417 , 5, 52.5–90.9 mm SL, Huila, Gigante, río Loro, 2°19'07.0"N, 75°36'54.0"W;
CZUT-IC 7861 , 10, 33.2–42.7 mm LS, Tolima, Ambalema, río Venadillo, 4°43'37.0"N, 74°50'54.0"W; CZUT-IC
8013 , 1, 92.5 mm SL, Cundinamarca, Vereda San Sumapaz, 4°11'40.0"N, 74°46'42.0"W; CZUT-IC 8251 , 2,
50.9–57.3 mm SL, Huila, Altamira, río Magdalena-Cauca, 2°10'20.0"N, 75°41'36.0"W; CZUT-IC 8467 , 1, 32.4
mm SL, Huila, Agrado, río Suaza, 2°10'03.0"N, 75°40'25.0"W; CZUT-IC 8551, 10, 51.5–96.7 mm LS, Tolima,
Ibagué, Quebrada Gualanday, 4°17'27.0"N, 75°02'13.0"W; CZUT-IC 8572 , 1, 47.9 mm SL, Tolima, Ibagué,
Quebrada Gualanday, 4°17'53.0"N, 75°02'18.0"W; CZUT-IC 10593 , 10, 56.7–90.8 mm mm LS, Tolima, Alvarado,
río Alvarado, 4°31'11.0"N, 74°59'14.0"W; ICNMHN 15528 , 3, 100.4–115.9 mm SL, Caldas, Norcasia, Cadenales,
río Manso, affluent of río La Miel, 5°42'40”N, 74°59'26”W; ICNMHN 15566 , 1, 146.7 mm SL, Caldas, Norcasia,
río Manso en La Samaria, 5°42'44”N, 74°50'22”W; ICNMHN 16268 , 13, 60.8–105.6 mm SL, Caldas, Norcasia,
río La Miel, 5°42'04”N, 74°45'49”W; ICNMHN 16923, 1, 123.68 mm SL, Caldas, río Guarinó, Puente Dorada,
5°18'44”N, 74°56'22”W. Chaetostoma platyrhynchus: All from Colombia. MPUJ 8233, 13, 24.8–52.5 mm SL,
Meta, San Juan de Arama, Río Güejar, 3°20'30.3"N, 73°56'56.2"W; MPUJ 8234, 31, 17.1–48.2 mm SL, Meta,
Vista Hermosa, Quebrada Sardinata, 3°01'07.1"N, 73°50'27.4"W. Chaetostoma strompoulos: All from Perú.
MZUSP 110476, 12, 63.6–89.9 mm SL, Huánuco, Tingo María, río Huallaga, 9º22'12"S, 75º58'37"W; MZUSP 13,
52.8–183.7 mm SL, Huánuco, Tingo María, Quebrada Cueva de Las Pavas, 9º22'15"S, 75º58'30"W.
Acknowledgements
Funding to conduct field work along the Orinoco River Basin piedmont was provided by the Pontificia Universidad
Javeriana (project No 5211411), University Vienna, Department of Integrative Zoology, and Department of
Morphology, Universidade Estadual Paulista—UNESP-, Instituto de Investigación de Recursos Biológicos
Alexander von Humboldt and Oleoducto Bicentenario (project No. 4400000166); and through a doctoral grant by
FAPESP to GAB (process 2014/11558-5). John Lundberg (ANSP), Saul Prada (MPUJ), and Francisco Villa
(CZUT) are acknowledged for the access to collections or loan of specimens. GAB acknowledges Sandra Reinales
and Carlos Sarmiento for their skillful advice on data analysis, and Tulio Teixeira for information about collections
of Chaetostoma from Perú housed at MZUSP. AU-B acknowledges fishermen Juan de Dios Ocampo and Josué
Ocampo, Anton Lamboj and Oliver Lucanus who facilitated and participated in the fieldwork at the Serranía de La
Macarena. The comments from two anonymous reviewers are also acknowledged for helping to improve the
quality of the manuscript. Donald Taphorn is acknowledged for kindly reviewing the English of the manuscript.
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... mosae Ballen, 2011, Chaetostoma joropo Ballen et al., 2016, Chaetostoma platyrhynchus (Fowler, 1943 and Chaetostoma vagum Fowler, 1943 are found east of the Andes in cis-Andean drainages (Amazon and Orinoco) (Ballen, 2011;Ballen et al., 2016;Chindoy et al., 2019). ...
... In the description of C. joropo, Ballen et al. (2016) mentions an additional, undescribed species of Chaetostoma from the Colombian Orinoco River basin available in museum collections. The main goals of this work are to describe this new species of Chaetostoma, to address the taxonomic status of three species from the Amazonian slopes in Colombia, to provide a key to the species from cis-Andean drainages in Colombia and to conduct an IUCN Red List assessment. ...
... The terminology of the lateral plate series follows Schaefer (1997). The term parieto-supraoccipital excrescence follows Ballen et al. (2016). An updated compilation of valid species names in the genus Chaetostoma was constructed with a programming recipe in the programme Emacs using Eschmeyer's Catalogue of Fishes (Fricke et al., 2020); the code is freely available at https://github.com/gaballench/validSppCatFishes. ...
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... S PECIES of Chaetostoma are popularly known as rubbernose plecos because they lack either plates, odontodes, or fleshy tentacles on the anterior and anterolateral portions of the snout, which is instead covered by soft skin and slime coat. Chaetostoma is the third most species-rich genus in the Hypostominae subfamily of the suckermouth armored catfish family Loricariidae (Lujan et al., 2015;Salcedo and Ortega, 2015;Ballen et al., 2016;Urbano-Bonilla and Ballen, 2021), and currently includes 49 valid species. Most species of Chaetostoma are distributed between approximately 80 to 2,500 m asl either in rivers along the eastern (cis-Andean) flanks of the Andes Mountains from Venezuela to southern Peru (n ¼ 24) or western (trans-Andean) flanks of the Andes from Panama to northern Peru (n ¼ 18). ...
... Material examined in addition to that listed in Ballen (2011), Ballen et al. (2016), Lujan et al. (2015), and Urbano-Bonilla and Ballen (2021). ...
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... Starting with the diagnostic character of the species among congeners, the presence of a fleshy keel on posterior tip of supraoccipital. This character is present in some species of Chaetostoma (Rapp Py- Daniel, 1991;Ceas & Page, 1996;Lasso & Provenzano, 1997;Ballen, 2011;Ballen, et al. 2016). However, the new species is not included in Chaetostoma because other external characteristics (see below) that are traditionally used to recognize species of this genus match partially or not at all. ...
... Inside the Chaetostoma group, this character is reported also for species of Dolichancistrus (Ballen & Vari, 2012). Species included in Transancistrus have a naked snout border, and species of Chaetostoma have a larger naked surface, mainly towards the dorsoanterior region of snout, in all species of these two genera there is no mention or report of the presence of any kind of odontodes, on naked areas of snout (Rapp Py-Daniel, 1991;Ceas & Page, 1996;Lasso & Provenzano, 1997;Salcedo, 2003Salcedo, , 2006aSalcedo, ,b, 2013Ballen, 2011;Tan & Armbruster, 2012;Salcedo & Ortega, 2015;Lujan, et al. 2015c;Ballen, et al. 2016). Species of Andeancistrus have a snout totally covered with plates, but lack enlarged odontodes, and A. platycephalus has keels on lateral body plates (Lujan, et al. 2015a). ...
... It may be that these patterns are not found in species that inhabit Colombia, or that our spiny pattern, subpattern C correspond to those types. Apparently, claw and spiny B patterns are the more common ones among the species of Chaetostoma (Rapp Py- Daniel, 1991;Ceas & Page, 1996;Lasso & Provenzano, 1997;Salcedo, 2003Salcedo, , 2006aSalcedo, ,b, 2013Ballen, 2011;Lujan, et al., 2015c;Ballen, et al., 2016). ...
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... The documentation of the ichthyofauna in cis-Andean Colombian sub-basins has been increasing during the last decade, but new records and species can likely still be found in areas previously thought to be well-sampled (e.g., Ballen 2011, Vanegas-Ríos et al. 2015, Ballen et al. 2016a, 2016b, Burns et al. 2017, García-Alzate et al. 2017). Most of the sampling effort has been carried out in the piedmont and lowland areas in the Cusiana as well as in other sub-basins, and exploration of High Andean areas could lead to the discovery of local endemic species at the basin scale that usually are underestimated (Carvajal-Quintero et al. 2015). ...
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... There are two other species belonging to different families of catfishes that also exhibit a similar distribution pattern: Centromochlus altae Fowler, 1945 (Auchenipteridae) (DoNascimiento pers. obs.) and Chaetostoma platyrhynchus (Fowler, 1943) (Loricariidae) (Ballen et al. 2016). Further investigations to detect other species with similar disjunct distributions in the Caquetá and Meta rivers are required to assess this biogeographic pattern and test hypotheses of past connections between these Andean tributaries of the Amazon and Orinoco rivers. ...
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This chapter examines the small, local, river fish faunas in the Magdalena and Maracaibo basins in Northern South America (NSA). It analyzes species richness and distribution patterns of the freshwater fishes of the coast of NSA to delimit biogeographic units and relate them to historical and ecological variables. It evaluates the application of techniques of classification and ordination to the river fish faunas and describes the evolution of ichthyofaunas in the Magdalena and Maracaibo drainages.
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The genus Otocinclus Cope (1872) of the siluriform family Loricariidae is diagnosed as monophyletic on the basis of shared derived characters of the cranial and hyobranchial skeleton, dorsal gill arch musculature, and gut. Otocinclus are relatively small herbivorous catfishes restricted to small streams and quiet slow-flowing margins of larger rivers, most frequently living in close association with aquatic macrophytes and terrestrial marginal grasses extending into the water column. Otocinclus species share a novel modification of the distal esophageal wall which is developed into an accessory blind diverticulum that may function in aerial respiration and for providing additional modulatory positive buoyancy for remaining in the upper water column at stream margins. Otocinclus has no junior synonyms, however several nominal species originally described in Otocinclus are here formally re-assigned to other genera in the subfamily Hypoptopomatinae. Otocinclus cephalacanthus Ribeiro 1911, O. depressicauda Ribeiro 1918, O. francirochai Ihering 1928, O. laevior Cope 1894, O. leptochilus Cope 1894, O. maculipinnis Regan 1904, O. nigricauda Boulenger 1891, and O. paulinus Regan 1908 are all placed in the genus Microlepidogaster Eigenmann & Eigenmann 1889; O. obtusos Ribeiro 1911 was placed in Pseudotothyris Britski & Garavello 1984; the genus Nannoptopoma Schaefer 1996 was erected for O. spectabilis Eigenmann 1914 in the tribe Hypoptopomatini; O. gibbosus Ribeiro 1908 is removed from Otocinclus, yet remains of undetermined generic status. Thirteen species are recognized in Otocinclus: O. affinis Steindachner 1877 of the lower Paraná/Paraguay and Uruguay basins and coastal streams of southeastern Brazil; O. bororo n. sp. of the upper Río Paraguay; O. caxarari n. sp. of the middle Río Guaporé/Mamoré system; O. flexilis Cope 1894 of the lower Paraná/Paraguay and Uruguay basins and coastal streams of southeastern Brazil; O. hasemani Steindachner 1915 of northern Brazil; O. hoppei Ribeiro 1939 of the upper Amazon, Tocantins and Paraguay basins and coastal streams of northeastern Brazil; O. huaorani n. sp. of the upper Amazon and Orinoco basins; O. macrospilus Eigenmann & Allen 1942 of the upper Amazon basin of Colombia, Ecuador, and Peru; O. mariae Fowler 1940 of the lower Amazon, upper Madeira and Paraguay basins; O. mura n. sp. of the middle Amazon River; O. vestitus Cope 1872 of the upper Amazon and lower Paraná basins; O. vittatus Regan 1904 of the Amazon, Orinoco, Paraná/Paraguay, and Tocantins basins; and O. xakriaba n. sp. of the rio São Fransisco basin. Two species are placed in synonymy: Otocinclus arnoldi Regan 1909 and O. fimbriatus Cope 1894 are junior synonyms of O. flexilis. Keys to the species of Otocinclus and genera of the Hypoptopomatinae are provided. A descriptive treatment of the osteology and cranial myology is provided for O. vittatus. Detailed analysis of meristic and morphometric variation based on geometric morphometric procedures is provided for the phenetically similar species pairs O. mariae and O. vittatus, O. bororo and O. huaorani in an a posteriori evaluation of separate species status. The phylogenetic relationships among Otocinclus species, and the phylogenetic position of Otocinclus among genera of the Hypoptopomatinae, are determined based on analysis of 27 morphological features using cladistic parsimony. Monophyly of Otocinclus was confirmed; within Otocinclus, a clade comprised of O. affinis and O. flexilis is the sister-group to the remainder of the genus. Within that latter clade, O. hasemani and O. xakriaba are the first and second-level sister-groups to the remainder of the genus, within which relationships among species are not fully resolved with available data. The phylogenetic biogeography of Otocinclus is informative regarding the historical relationships among major river drainage basins, particularly of those river systems of the Brazilian Shield. A biogeographic hypothesis is proposed based on the area cladogram derived from the species-level phylogenetic relationships, which suggests successive vicariance and speciation in the non-Amazonian regions of endemism of southeastern and eastern South America, followed by speciation and dispersal within the Amazon, Orinoco and upper Paraguay basins. The pattern of vicariance revealed by the Otocinclus species-level phylogeny is congruent with the geologic history of the major river drainage basins of the Brazilian Shield. This result suggests that, for Otocinclus and perhaps other loricariid catfishes, much of their generic and species-level diversification occurred prior to the formation of the Amazon basin.
Article
The new Chaetostoma-group genera Andeancistrus and Transancistrus are described based on recently collected material from rivers draining the respective Amazonian and Pacific slopes of the Andes Mountains in Ecuador. Andeancistrus is diagnosable from all other members of the Chaetostoma group by having a fully plated snout, lacking cheek odontodes that extend past the opercular flap, and by having eight vs. nine branched dorsal-fin rays. The new species Andeancistrus eschwartzae is also described and diagnosed from its only congener (A. platycephalus) by having a black to dark gray base color of head and body (vs. light gray), irregularly shaped round to vermiculate yellow-gold spots smaller than half naris diameter evenly distributed across head, lateral and dorsal surfaces of the body and fin rays (vs. white to blue uniformly round spots), and by lacking enlarged clusters of odontodes at the posteromedial apex of most lateral body plates (vs. odontode clusters present). Transancistrus contains the species T. aequinoctialis and T. santarosensis, which can together be diagnosed from all other members of the Chaetostoma group except Chaetostoma by lacking plates along the anterior and lateral margins of the snout; they can be diagnosed from Chaetostoma by having a much narrower unplated snout region, approximately as wide as the maximum diameter of the orbit (vs. twice this width). Geographic distributions exclusive of drainages north of Ecuador and strong molecular phylogenetic evidence for a sister relationship between Andeancistrus and Transancistrus support the hypothesis that these genera may have once been contiguously distributed through a low-lying region of northern Peru and been separated via uplift of the Andes Mountains. © 2015 by the American Society of Ichthyologists and Herpetologists.