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Accepted by J. Armbruster: 27 Jan. 2017; published: 20 Mar. 2017
ZOOTAXA
ISSN 1175-5326 (print edition)
ISSN
1175-5334
(online edition)
Copyright © 2017 Magnolia Press
Zootaxa 4244 (2): 207
–
218
http://www.mapress.com/j/zt/
Article
207
https://doi.org/10.11646/zootaxa.4244.2.3
http://zoobank.org/urn:lsid:zoobank.org:pub:440F5BF3-CC82-42AF-BB78-2C415AD519AA
Ituglanis compactus, a new species of catfish (Siluriformes: Trichomycteridae)
from the rio Jari drainage, lower Amazon, Brazil
ÍTHALO DA SILVA CASTRO
1
& WOLMAR BENJAMIN WOSIACKI
1,2
1
Departamento de Ictiologia, Coordenação de Zoologia, Museu Paraense Emílio Goeldi, Av. Magalhães Barata, 376, São Braz,
Belém, PA, Brazil, CP 399, CEP 66040–170 Brasil. E-mail: wolmar@museu-goeldi.br, ithalocastro@hotmail.com
2
Corresponding author
Abstract
A new species of Ituglanis is described from rio Iratapuru, near the rio Jari, Amapá, Brazil. The new species is distingui-
shed from all congeners by the reduced number of post-Weberian apparatus vertebrae (36 or 37); the low number of paired
ribs (2); the low number of interopercular odontodes (12–15); the number of branchiostegal rays (7 or 8); the presence of
elongated fontanel in parieto-supraoccipital; the pectoral-fin rays (i,5); head length (18.9–25.0); and the presence of pores
supraorbital s1, infraorbitals i1 and i3 of the laterosensory system. The new taxon has a reduced body size and fully ossi-
fied skeleton, but does not display a large number of paedomorphic traits compared to congeners. Comments about taxo-
nomy and intrageneric comparisons are made, and paedomorphic in Ituglanis is discussed. Thoughts about conservation
of the new species are presented.
Key words: Taxonomy, Osteology, Paedomorphosis, Freshwater, Neotropical
Resumo
Uma nova espécie de Ituglanis é descrita do rio Iratapuru, próximo ao rio Jari, Amapá, Brasil. Distingue-se das demais
congêneres pelas seguintes características: reduzido número de vértebras pós aparato Weberiano (36–37); baixo número
de pares de costelas (2); pelo reduzido número de odontódios interoperculares (12–15); raios branquiostegais (7–8); pre-
sença de fontanela alongada no parieto-supraoccipital; pelos raios da nadadeira peitoral (i,5); comprimento da cabeça
(18,9–25,0) e presença do poro supraorbital s1 e dos infraorbitais i1 e i3 do sistema látero-sensorial. A nova espécie apre-
senta tamanho do corpo reduzido e esqueleto completamente ossificado, porém não exibe um grande número de caracteres
pedomórficos quando comparada às congêneres. Comentários sobre taxonomia são feitos, comparações intragenéricas e
pedomorfose em Ituglanis são abordados. Considerações sobre a conservação da nova espécie são apresentados.
Introduction
The genus Ituglanis (Trichomycteridae) was proposed by Costa & Bockmann (1993) for nine species formerly
assigned to Trichomycterus. These form a natural group and share three derived characteristics of cranial
osteology: (1) posterior fontanel with a small orifice on the parieto-supraoccipital; (2) anterior portion of the
sphenotic-prootic-pterosphenoid with anterior projection; (3) autopalatine with a deep concavity on its median
anterior edge. Currently, Ituglanis comprises 26 valid species (Eschmeyer et al., 2016), most of which were
described in the last five years (Wosiacki et al., 2012; Lima et al., 2013; Datovo, 2014; Datovo & de Pinna, 2014;
Rizzato & Bichuette, 2014; Ferrer et al., 2015; Datovo et al., 2016), and which are distributed among river basins
in South America east of the Andes. Some species of the genus are found exclusively in caves of northeastern
Goiás State, exhibiting typical troglomorphic characteristics such as reduced eyes and sparse bodily pigmentation
(Bichuette & Trajano, 2004, 2008). Ituglanis includes species ranging from as large as 170 mm standard length
(SL) to others of extremely small size, reaching a maximum of 50 mm SL (de Pinna & Wosiacki, 2003) and having
a large number of reductive morphological characters for the genus (Datovo & Landim, 2005).
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Many species of Ostariophysan fish are considered miniatures (Toledo-Piza et al., 2014) because they do not
exceed the arbitrary maximum of 26 mm SL as adults or attain sexual maturity at under 20 mm SL (Weitzman &
Vari, 1988). Moreover, many species included within these parameters show a greater tendency towards
paedomorphosis, that is, the reduction, loss or fusion of bones and truncation of the laterosensory system
(Weitzman & Vari, 1988). Many small species (including many ostariophysan species and several trichomycterids)
have been described recently, and these species all share some characteristic related to the miniaturization process
(de Pinna & Wosiacki, 2002; Wosiacki et al., 2011; Dutra et al., 2012). In this paper, a new species of Ituglanis is
described from the rio Iratapuru, a tributary of the rio Jari in Amapá state, Brazil. Possible relationships among
species and paedomorphosis in the genus are discussed.
Methods
Measurements were made point to point using digital calipers (0.1 mm precision) under a stereomicroscope. Snout
length was measured from the anterior margin of the eye to the most anterior part of the upper lip; length of the
pectoral fin was measured from the point immediately anterior of its origin to the extreme distal point of the first
ray; body height was measured transversally from the point of origin of the dorsal fin. Counts and measurements
follow Tchernavin (1944). Other measurements such as caudal peduncle and diameter of the eye follow de Pinna
(1992). Partial measurements are presented as percentage of standard length (SL), except for subunits of the head,
expressed as percentage of the head length. Counts and measurements were made preferentially on the left side.
The number of non-ramified rays are represented as lower case Roman numerals, and ramified rays as Arabic
numbers. Asterisks indicate holotype registers.
Osteological analysis was carried out on cleared and stained specimens (c&s) using the protocol of Taylor &
Van Dyke (1985). Osteological terminology follows Datovo & Landim (2005), except for the caudal skeletal,
which follows Arratia (1983). Vertebral counts do not include the Weberian apparatus and the compound caudal
centrum. Nomenclature and homology in the laterosensory system follow Arratia & Huaquín (1995) except for the
post-otic branch, which is in accord with Bockmann et al. (2004). Illustrations were made using a stereomicroscope
with a camera lucida attachment.
Osteological data for Ituglanis herberti (Miranda Ribeiro 1940) was obtained from X-ray images provided by
the National Museum of Natural History (USNM) and the original literature (Datovo & Landim, 2005; Lima et al.,
2013). Institutional abbreviations: INPA, Instituto de Pesquisas da Amazônia, Manaus; MCP, Museu de Ciências e
Tecnologia da Pontifícia Universidade Católica do Rio Grande do Sul, Porto Alegre; MNRJ, Museu Nacional do
Rio de Janeiro, Rio de Janeiro; MPEG, Museu Paraense Emílio Goeldi, Belém; MZUSP, Museu de Zoologia da
Universidade de São Paulo, São Paulo; NMW, Naturhistorisches Museum, Wien.
Ituglanis compactus, new species
(Figs. 1 and 2, Table 1)
Holotype. INPA–ICT 053200, 25.6 mm SL, Brazil, Amapá, Laranjal do Jari municipality, rio Iratapuru, left
tributary of the rio Jari; June 1987; M. Jégu & J. Zuanon.
Paratypes. INPA 13006, 35 + 1c&s (12.5–25.8 mm SL); MPEG 34486, 4 + 4 c&s, (18.6–25.6 mm SL);
MZUSP 121276, 5, (16.8–21.6 mm SL), same data as holotype.
Diagnosis. Ituglanis compactus is distinguished from all other congeners, except I. amazonicus (Steindachner
1882), I. apteryx Datovo 2014, I. eichhorniarum (Miranda Ribeiro 1912), I. gracilior (Eigenmann 1912), I. ina
Wosiacki, Dutra & Mendonça 2012, I. macunaima Datovo & Landim 2005, I. nebulosus de Pinna & Keith 2003,
and I. parkoi (Miranda Ribeiro 1944), by the number of ribs reduced to two pairs (vs. four in I. cahyensis
Sarmento-Soares, Martins-Pinheiro, Aranda & Chamon 2006; five in I. epikarstikus Bichuette & Trajano 2004;
five or six in I. agreste Lima, Neves & Campos-Paiva 2013, I. australis Datovo & de Pinna 2014, and I. boitata
Ferrer, Donin & Malabarba 2015; six in I. mambai Bichuette & Trajano 2008, I. paraguassuensis Campos-Paiva &
Costa 2007, I. parahybae (Eigenmann 1918), and I. proops (Miranda Ribeiro 1908); six or seven in I. bambui
Bichuette & Trajano 2004 and I. ramiroi Bichuette & Trajano 2004; 6–8 in I. passensis Fernández & Bichuette
2002; and six to eight in I. boticario Rizzato & Bichuette 2014). Moreover, I. compactus differs in the smaller
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A NEW SPECIES OF ITUGLANIS
number of vertebrae, 36 or 37 (vs. 38 or 39 in I. eichhorniarum; 38–40 in I. ina; 41–43 in I. amazonicus, I.
gracilior; 42 in I. metae (Eigenmann 1917); 42 or 43 in I. herberti; 43 in I. parkoi; and 43–45 in I. apteryx).
Ituglanis compactus also differs from I. guayaberensis (Dahl 1960), and I. parkoi in the rounded caudal fin (vs.
truncate). Ituglanis compactus is distinguished from I. nebulosus in the reduced number of interopercular
odontodes, 12–15 (vs. 17); and seven or eight branchiostegal rays (vs. six). Ituglanis compactus is distinguished
from I. nebulosus and I. amazonicus by the presence of an elongated fontanel in the parieto-supraoccipital (vs.
fontanel reduced to a small orifice). Ituglanis compactus differs from I. macunaima by the presence of a fontanel in
the parieto-supraoccipital (vs. absent); by the presence of cephalic pores s1, i1 and i3 (vs. absent) and by the
number of rays in the pectoral fins i,5 (vs. i,4). Ituglanis compactus also differs from I. amazonicus by the head
length, 18.9–25.0 (vs. 14.5–17.9). Ituglanis compactus is distinguished from I. goya Datovo, Aquino & Langeani
2016 by the presence of the anterior cranial fontanel (vs. absence). Ituglanis compactus is distinguished from I.
laticeps (Kner 1863) by caudal peduncle length 7.8–8.5 in standard length [vs. 5.5; Eigenmann (1918)].
Description. Species of small size, largest specimen, 25.8 mm SL. Morphometric data in Table 1. Body
elongate and laterally compressed in posterior direction. Dorsal profile of body slightly convex, ventral profile of
body straight (Fig. 1).
TABLE 1. Morphometric data of Ituglanis compactus (holotype and 49 paratypes). SD: Standard deviation.
Head longer than wide, slightly depressed, trapezoidal in dorsal view, wider at posterior margin of opercle.
Anterior margin of snout slightly elongated. Eyes rounded located dorsally on anterior half of head; without free
margin, orbits covered by fine and translucent membrane. Anterior nostril encircled by membrane forming small
tube from which nasal barbel extends. Posterior nostril located nearer margin of orbit than anterior nostril,
occluded anteriorly by fold of integument shaped like a half-shell.
Holotype Range
(Min.–Max.)
Mean SD
Standard length (mm) 25.6 12.5–25.8 – –
Percents of Standard Length
Total length 119.8 114.4–125.9 120.1 2.2
Body depth 16.1 11.7–17.0 14.3 1.3
Caudal peduncle depth 11.6 8.9–12.5 10.7 0.7
Caudal peduncle length 14.9 11.1–19.7 15.4 1.6
Predorsal length 74.5 70.0–80.5 75.2 2.3
Preanal length 75.4 71.7–80.3 76.0 1.7
Prepelvic length 62.5 59.8–74.3 67.0 2.5
Dorsal-fin base length 9.4 7.2–13.2 10.2 1.2
Anal-fin base length 8.9 7.3–10.6 8.9 0.7
First pectoral-fin length 9.8 9.8–22.5 16.1 2.4
Head length 18.9 18.9–25.0 20.8 1.0
Percents of Head Length
Head depth 86.4 74.4–101.7 84.8 5.5
Head width 41.0 34.3–58.2 48.0 5.1
Interorbital width 24.2 21.4–31.5 25.9 2.3
Snout length 26.4 19.8–33.5 27.3 2.5
Eye diameter 10.1 6.9–12.9 9.9 1.0
Width of mouth 49.6 36.3–54.2 46.1 4.1
Nasal barbel length 50.0 33.5–63.6 51.1 6.6
Maxilar barbel length 81.8 34.9–97.6 77.5 13.6
Rictal barbel length 55.8 22.8–80.3 56.2 12.7
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Mouth subterminal, margins slightly curved ventrally in frontal view; lower lip with fold of integument
continuous with base of rictal barbel. Maxillary barbel depressed and elongated, inserted at corner of mouth; distal
extremity passing insertion of pectoral fin when distended. Rictal barbel under maxillary barbel; extremity not
reaching posterior portion of insertion of pectoral fin. Nasal barbel located laterally from anterior nostril; distal
extremity reaching posterior portion of opercular patch of odontodes. Branchial membrane thick, attached to
isthmus at anterior portion.
Pectoral fin inserted just posterior to interopercular patch of odontodes (Fig. 2); pectoral-fin rays i,5(33*) or
i,6(17); first ray not branched, more robust than the others, distinctly longer, up to 17.8% of SL, prolonged as
filament; remaining rays with one branch, getting gradually smaller, making margin oblique. Pelvic-fin rays, i,4;
distal edge of pelvic fin when depressed not passing origin of anal-fin. Anal and urogenital openings at posterior
half of length of pelvic fin. Dorsal fin semicircular, distal margin rounded, origin on posterior half of body; dorsal
rays, ii,6(7) or ii,7(43*); branched rays single branching; two or three supernumerary rays anterior to origin. Anal-
fin origin on line passing over base of first branched ray of dorsal fin; length base similar to dorsal-fin base, distal
margin rounded; anal-fin rays, ii,5.
FIGURE 1. Ituglanis compactus, INPA 13006, holotype, 25.6 mm SL, lateral view of left side; Brazil, Amapá, Laranjal do
Jari, rio Iratapuru, tributary of the rio Jari.
FIGURE 2. Ituglanis compactus, INPA 13006, holotype; lateral view of left side of head. Scale bar = 2 mm.
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Caudal peduncle short and compressed. Caudal fin slightly rounded; principal caudal-fin rays, i,5/5,ii(4), i,5/
6,i(45*) or i,6/6,i(1). Procurrent caudal-fin rays beginning at anterior half-length of caudal peduncle; 10–14
dorsally and 9–11 ventrally.
Osteology. Anterior margin of mesethmoid straight, wide axis. Conspicuous concavity in anterior margin of
autopalatine; posterior process moderately long and wide at base. Premaxilla rectangular, two regular rows of 13–
16 conical teeth. Triangular mandible, two irregular rows of 15–18 conical teeth. Sphenotic in anterior direction.
Sphenotic, prootic, and pterosphenotic fused with anterior projection and opening of infraorbital sensory canal.
Fontanels restricted to a small opening; anterior elongated between frontals, posterior at parieto-supraoccipital.
Weberian apparatus with small lateral openings and tiny pores along its entire surface (Fig. 3).
FIGURE 3. Dorsal view of skull and Weberian apparatus of Ituglanis compactus, paratype, INPA 13006, 22.4 mm SL. AOR,
antorbital; APA, autopalatine; EPO, epioccipital; FRO, frontal; i1–11, infraorbital sensory pores 1 to 11; laf, ramus lateralis
acessorius facialis foramen; LET, lateral ethmoid; MAX, maxila; MET, mesethmoid; PMX, premaxila; po1–2, postotic sensory
pores 1 to 2; PSC, “posttemporosupracleithrum”; PSO, parieto-supraoccipital; PTE, pterotic; SOR, supraorbital tendon-bone;
s1–6, supraorbital sensory pores 1 to 6; SPH+POT+PSF, sphenotic+prootic+pterosphenoid; WEB, Weberian apparatus. Left
laterosensory canals and pores do not view. Scale bar = 1 mm.
Opercular patch of odontodes small and rounded, arranged dorsolaterally in posterior region of head, reaching
base of pectoral fin; 8–10 long, straight odontodes. Interopercular patch of odontodes elongated, curved in
posterior region, arranged ventrolaterally on head, slightly anterior of opercular patch; 12–15 long, straight
odontodes (Fig. 4).
Urohyal with two long, lateral, laminar processes, wide from base to medial portion, narrowing gradually
towards distal extremity. Branchiostegal rays seven or eight, seventh notably expanded in its posterior extremity.
First basibranchial absent, second and third basibranchials ossified with cartilaginous extremities; fourth
basibranchial elongated and cartilaginous. First hypobranchial ossified, elongated and slightly twisted; second
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hypobranchial elongated, slightly trapezoidal, mostly cartilaginous, anterolateral process ossified; third
hypobranchial depressed, mostly cartilaginous, anterolateral process ossified too. First, second, third, and fourth
ceratobranchials ossified, cartilaginous extremities; fifth ceratobranchial curved, small teeth present on anterior
half. First epibranchial with long anterior process; second epibranchial with two small alternating processes; third
with rounded posterior process; fourth flattened, slightly rectangular; fifth reduced, cartilaginous when present.
First and second pharyngobranchials absent; third and fourth slightly twisted, fourth attached to dental plate.
Pharyngeal dental plate with conical teeth arranged ventromedially in two rows.
FIGURE 4. Left view of the suspensorial and opercular series of Ituglanis compactus, paratype, INPA 13006, 22.4 mm SL.
HYO, hyomandibula; IOP, interopercle; MPT, metapterygoid; OPE, opercle; POP, preopercle; QUA, quadrate. Scale bar = 0.5
mm.
Cleithrum approximately rectangular or triangular in ventral view. Scapulocoracoid in lateral region of
cleithrum, approximately rectangular in ventral view.
Two pairs of ribs. First hemal canal complete on third vertebrae after Weberian apparatus. First hemal spine
complete between vertebrae 14 and 16. Total number of vertebrae 36 or 37. Two vertebrae between first
pterygiophore of dorsal fin and first pterygiophore of anal fin. Eight dorsal pterygiophores located between neural
spines of vertebrae 23 and 27. Six anal pterygiophores between hemal spines of vertebrae 24 and 27.
Caudal skeleton composed of the parhypural fused to hypurals 1 and 2, hypural plates fused, probably 3 and 4,
and hypural 5 free. Uroneural, central preural 1 and neural arch of central preural 1 fused. Neural and hemal spines
of the preural centrum 2 (Fig. 5a).
Pores present on cephalic laterosensory canals. Supraorbital pores s1, s3, and s6 supraorbital; s1 between and
immediately behind anterior nostril; s3 between and just behind posterior nostril; s6 posterior to interorbital region.
Pores i1 and i3 of infraorbital canal located anteriorly, near base of nasal barbel; i10 and i11 located
posteroventrally to interorbital region. Pores po1 and po2 of postotic canal, po1 anterodorsal to opercular patch of
odontodes and po2 posterolateral to opercular patch of odontodes. Lateral line short, with two pores, ll1 and ll2,
posteriorly to opercle and posterodorsal to pectoral-fin base.
Coloration in alcohol. Specimens contain no chromatophores on body, pale yellow to light orange coloration
in dorsolateral region, gradually becoming lighter in ventral and caudal regions, probably due the long date and
exposure to light.
Notes on conservation. Ituglanis compactus was found only along the rio Iratapuru. It occurs outside the
boundaries of two protected areas in Amapá State, the rio Cajari Extractive Reserve (RESEX), a federal
conservation area for sustainable use with an area of 481,650 hectares, and the Uitapuru Sustainable Development
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Reserve (RDS) with an area of 806,180 hectares. The main threat to the conservation of Ituglanis compactus is the
hydroelectric dam of Santo Antônio do Jari, located between the municipalities of Almeirim in Pará and Laranjal
do Jari in Amapá, because it abruptly alters the natural characteristics of the regional aquatic ecosystem and can
affect the survival of this and other species.
Distribution. Ituglanis compactus is known only from the type locality on the rio Iratapuru, a left-bank
tributary of the rio Jari, Amapá State, Brazil (Fig. 6).
Etymology. From the Latin, compactus; in reference to the small body size and internal and external characters
maintained compared to the larger size congeners.
FIGURE 5. Left side view of the caudal skeleton. a) Ituglanis compactus, INPA 13006, 22.4 mm SL; b) Ituglanis gracilior,
MCP 36241, 42.4 mm SL; c) Ituglanis macunaima, MZUSP 103799, 46.3 mm SL; d) Ituglanis proops, MZUSP 60255, 55.6
mm SL. NPU1, neural arch of the preural centrum 1; PU1+U1, compound centrum formed from preural 1 and ural centrum 1;
PU2, preural centrum 2; HE, hemal spine; NE, neural spine; NSPU1, neural spine of the preural centrum 1; H3, hypural 3;
H4+H5, hypurals 4 and 5 fused; H3+H4+H5, hypurals 3, 4 and 5 fused; PH+H1+H2, parhypural and hypurals 1 and 2 fused;
UN, uroneural. Scale bar = 1 mm.
Discussion
Ituglanis compactus has the three osteological synapomorphies of the neurocranium proposed by Costa &
Bockmann (1993): posterior fontanel reduced to a small orifice in the parieto-supraoccipital; sphenotic-prootic-
pterosphenoid with its anterior portion oriented in anterior direction; and autopalatine with median anterior border
with a deep concavity. Wosiacki (2002) proposed two additional characters for Ituglanis: (1) presence of two
vertebrae between the first pterygiophore of the dorsal fin and the first of the anal fin; and (2) 23 or more free
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vertebrae anterior to the first pterygiophore of the dorsal fin. Thus, I. compactus is justifiably included in the genus
because it shares character 1 (two vertebrae between the first pterygiophore of the dorsal fin and the first of the anal
fin) as proposed by Wosiacki (2002).
De Pinna & Keith (2003) proposed the existence of a northern clade, with species distributed among
Amazonian and Guianan river basins, sharing a reduction to three pair of ribs or fewer, also present in I. compactus,
and also occurring in the northern part of South America. However, later studies have refuted the hypothesis of a
northern clade (Datovo & Landim, 2005; Sarmento-Soares et al., 2006), given that more recently described species
have geographical distributions incongruent with the characteristics proposed by de Pinna & Keith (2003). If the
northern clade hypothesis of de Pinna & Keith (2003) is corroborated, I. compactus could belong to a less inclusive
clade formed by the species I. nebulosus, I. amazonicus and Ituglanis sp. 2, including within it species with a larger
mesethmoid.
The reduced size but elongated shape of the cranial fontanel on the parieto-supraoccipital in I. compactus is a
character shared with I. parkoi. This is likely a derived state intermediate between the elongated fontanel observed
in most Trichomycteridae and Siluriformes, comprising the plesiomorphic state, and the fontanel reduced to an
orifice in the posterior region of the parieto-supraoccipital (Costa & Bockmann, 1993) as in I. agreste, I. bambui, I.
amazonicus, I. parahybae, and I. ramiroi, or absent, as in the most extreme derived state as found in I. apteryx, I.
macunaima, I. mambai, and some specimens of I. epikarstikus (Bichuette & Trajano, 2004, 2008; Datovo &
Landim, 2005).
The skeleton of the specimens of I. compactus examined are completely ossified, with edges of the
neurocranial bones, three hypobranchials and hypurals on upper (H3, H4+H5) and lower (PH+H1+H2) caudal
plates having well-defined borders and strong calcification, indicating that these specimens analyzed reached adult
size (de Pinna, 1989; de Pinna & Ng, 2004). In addition, the analysis of juvenile of I. gracilior and I. ina with the
same size as the large specimens of I. compactus demonstrated considerable difference in the level of ossification.
The margins of the bones of juvenile specimens have a high amount of cartilage, as opposed to the defined and
ossified edges of I. compactus, leaving no doubt of the adult ontogenetic stage of the new species.
Ituglanis compactus does not have marked paedomorphic characters in relation to other congeners. The small
number of odontodes (8–10 in the opercle and 12–15 in the interopercle) and the reduced number of vertebrae in I.
compactus (36 or 37 vertebrae after the Weberian apparatus) is also observed in I. macunaima and in some cave-
dwelling species like I. bambui, I. ramiroi, and I. epikarstikus, and other non-cave dwelling species like I.
nebulosus (35 or 36), I. passensis (36), and I. agreste (36), many of which are larger than 26 mm SL. The
remaining species have a higher number of vertebrae after the Weberian apparatus, such as I. parkoi and some
specimens of I. amazonicus and I. herberti (43), and I. ina (43–45). The extreme reduction to three or fewer pairs
of ribs in I. compactus is observed in other species of the so-called northern clade.
The caudal skeleton of Ituglanis compactus has a very short neural spine on the preural centrum 1, similar to
the condition found in I. gracilior. However, this structure becomes gradually larger in I. macunaima and becomes
almost half the length of the uroneural in I. proops. Ituglanis compactus exhibits, moreover, a distinct pattern of
fusion between the hypurals (H3, H4+H5) when compared with I. proops (H3+H4+H5), but shows the same
pattern as I. gracilior and I. macunaima (H3, H4+H5) (Fig. 5). This pattern of distinctive fusions suggests a
progressive characteristic, not just a reductive one for the genus, and thus is not necessarily related to
paedomorphosis or to miniaturization in Ituglanis.
The lateral line and cephalic sensory canals in Ituglanis compactus are formed by simple, non-ramified
branches, following the pattern for the group (de Pinna, 1998), while not presenting structural reduction when
compared to congeners. A supraorbital canal with pores s1, s3 e s6 is present, as well as infraorbitals i1, i3, i10 e
i11. The absence of pore s2 is a character shared with other species of Ituglanis of larger sizes, including I.
amazonicus, I. apteryx, I. parkoi, and I. macunaima. Pores i10 and i11 are present, as well as pores po1 and po2 of
the post-otic canal. The short lateral line in I. compactus is not modified, and exhibits pores ll1 and ll2,
characteristic of the genus and most of the Trichomycteridae non-Copionodontinae, Trichogenes, Bullockia, and
Hatcheria.
Ituglanis compactus presents a small anterior process of the hyomandibula and reduced area of quadrate in
relation to congeners, but these processes are proportionally larger when compared to other species of the family. In
the clade TSVSG, species such as Sarcoglanis simplex Myers & Weitzman 1966, Ammoglanis diaphanus Costa
1994 and Microcambeva ribeirae Costa, Lima & Bizerril 2004 (Sarcoglanidinae), Vandellia sanguinea Eigenmann
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1917 (Vandelliinae), and Listrura tetraradiata Landim & Costa 2002 (Glanapteryginae) present the anterior
process of the hyomandibula as narrow, elongated and pointed. When present, the small posterior process of the
quadrate in these species is dorsally oriented. In the stegophiline Homodiaetus anisitsi Eigenmann & Ward 1907,
the anterior process of the hyomandibula presents a larger area. On the other hand, the tridentine Tridentopsis
pearsoni Myers 1925 exhibits a narrow and elongated hyomandibula process, curved and posteriorly oriented.
Miniature species, following the arbitrary definition of Weitzman & Vari (1988), are known from five of the
eight subfamilies of Trichomycteridae: Trichomycterinae, Tridentinae, Sarcoglanidinae, Stegophilinae, and
Glanapteryginae (Toledo-Piza et al., 2014). Regardless of which of the competing hypotheses about relationships
among the Trichomycteridae turns out to be correct (Baskin, 1973; de Pinna, 1989; Wosiacki, 2002; Datovo &
Bockmann, 2010), the description of I. compactus suggests there may have been at least five events of
miniaturization in the family.
FIGURE 6. Geographic distribution of Ituglanis compactus, indicating type locality (yellow circle) in the rio Iratapuru, a
tributary of the rio Jari, Amapá, Brazil.
Comparative material: Ammoglanis diaphanus; MZUSP 86249, 2 c&s, 12.6–14.5 mm SL, Brazil, Tocantins,
rio Araguaia basin, Tocantins-Araguaia ecoregion. Homodiaetus anisitsi; MCP 9353, 2 c&s, 35.5–41.4 mm SL,
Brazil, Rio Uruguai basin, Lower Uruguay ecoregion. Ituglanis amazonicus; MPEG 3345, 1 c&s, 42.0 mm SL,
Brazil, Pará, Parauapebas, Serra dos Carajás, rio Itacaiúnas, igarapé do Pojuca; MPEG 28703, 1, 47.8 mm SL,
Pará, Jacareacanga, Tapajós basin, Vila da Mamãe Anã, unnamed stream; MNW43306, 1, 47.6 mm SL, picture of
holotype, Amazon basin, Codajás. MPEG 27869, 1, 55.2 mm SL, Pará, Jacareacanga, Vila de São Martins, Tapajós
basin; MPEG 24141, 1, 45.9 mm SL, Pará, Santarém, Resex Arapiuns-Tapajós, Comunidade Nova Canaã, rio
Maró, tributary of rio Arapiuns, Tapajós basin; MPEG 19084, 1, 52.1 mm SL, Pará, Oriximiná, FLOTA Trombetas,
Trombetas basin; MPEG 19086, 2, 40.2–56.2 mm SL, same as MPEG 19084. MPEG 6957, 1, 55.6 mm SL, Pará,
Paragominas, rio Igarapé da Trincheira, tributary of rio Paraquequara, Fazenda Monte Santo, Guamá-Capim basin;
MPEG 19091, 1, 47.6 mm SL, Pará, Alenquer, ESEC Grão Pará – T3 100, Curuá basin; MPEG 13656, 1, 42.4 mm
SL, Pará, Juruti, igarapé Socó, Tapajós basin; MPEG 19089, 1, 49.0 mm SL, Pará, Alenquer, ESEC Grão Pará Sul
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– T3 3000, Curuá basin. Ituglanis apteryx; MZUSP 96876, 1c&s, 67.2 mm SL, Brazil, Pará, Xingu basin, rio
Curuá, rio Iriri basin. Ituglanis australis; MCP 10420, 1 c&s, 40.0 mm SL; MCP 37695, 2 c&s, 52.4 mm SL,
Uruguay, Tacuarembó district, Ansina municipality, río Uruguai basin, río Tacuarembó. Ituglanis eichhorniarum;
MZUSP 37605, 2 c&s, 45.6–51.1 mm SL, Brazil, Mato Grosso, Cáceres, on the bank of the rio Paraguai. Ituglanis
gracilior; MCP 36241, 4 + 2 c&s, 26.3–42.4 mm SL, Brazil, Rondônia, Porto Velho, stream tributary on the left
margin of the rio Madeira, between Taquarás and igarapé Taquerás, along highway BR-425. Ituglanis macunaima;
MZUSP 103799, 2 + 2 c&s, 39.1–46.3 mm SL, Brazil, Mato Grosso, upper Taquari. Ituglanis ina; MPEG 17386, 5
c&s, 30.9–51.8 mm SL, Brazil, Pará, Parauapebas, Serra dos Carajás, affluent on the left margin of rio
Parauapebas, affluent on the right margin of rio Itacaiúnas, affluent on the right back of rio Tocantins. Ituglanis
nebulosus; MZUSP 69574, 1 c&s, 35.1 mm SL, French Guiana, río Arataye, tributary of río Approuague, near
Reserve naturelle des Nouragues. Ituglanis paraguassuensis; MZUSP 102703, 1 c&s, 43.0 mm SL, Brazil, Bahia,
Itororo, stream tributary of rio Cachoeira. Ituglanis passensis; MZUSP 80098, 1 c&s, 46.5 mm SL, Brazil, Goiás,
Passa Três cave, rio Paranã basin, Alto Tocantins. Ituglanis proops; MZUSP 60255, 2 c&s, 55.6–69.2 mm SL,
Brazil, São Paulo, locality neighborhood Córrego da Onça, Córrego da Onça, affluent of rio Pardo; MZUSP
65750, 2 c&s, 45.8–49.4 mm SL, Brazil, São Paulo, Sete Barras, rio Quilombo, Carlos Botelho State Park, about
50 km about the mouth of rio Saibadela. Listrura tetraradiata; MNRJ 19064, 2 c&s, 36.0–39.2 mm SL, Brazil,
Saquarema Municipality, rio da Represa, rio Ibicuíba basin. Microcambeva ribeirae; MZUSP 68169, 3 c&s, 37.7–
41.8 mm SL, Brazil, São Paulo, Rio Ribeira de Iguape basin/ecoregion. Sarcoglanis simplex; INPA 8165, 2 c&s,
14.2–18.5 mm SL, Brazil, Rio Branco basin, Amazonas Guiana Shield ecoregion. Tridentopsis pearsoni; MNRJ
39071, 2 c&s, 17.0–21.6 mm SL, Río Napo basin, Marañon-Napo-Caqueta ecoregion, Ecuador. Vandellia
sanguinea; MZUSP 63395, 5 c&s, 50.6–69.1 mm SL, Brazil, Rio Madeira basin, Madeira Brazilian Shield
ecoregion.
Acknowledgments
The authors thank L. Rapp Py-Daniel (INPA), M. C. C. de Pinna and A. Datovo (MZUSP), M. Lucena (MCP), and
M. Britto (MNRJ), for loan material and assistance during visits to collections; A G. M. Dutra, A. Akama, A.
Netto-Ferreira, and G. M. T. Mattox for critical review and generous contributions to this manuscript. The authors
thank the Conselho Nacional de Desenvolvimento Científico e Tecnológico, CNPq (WBW, grants 300940/2015–7
and 405144/2013–0), CAPES (ISC, grant 2471906/14), and PROAP-CAPES (ISC, grant 23073.017704/2015–58).
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