Trichomycterus (Paracambeva) antiquus Costa & Feltrin & Mattos & Katz 2024, sp. nov.
Creators: name: Costa, Wilson J. E. M.
name: Feltrin, Caio R. M.
name: Mattos, José Leonardo O.
name: Katz, Axel M.
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Siluriformes
Trichomycteridae
Trichomycterus
Trichomycterus antiquus

description: Trichomycterus (Paracambeva) antiquus sp. nov.
Figs 1, 2, 3, Table 3
Type material.
Holotype. Brazil • 1 ex., 72.2 mm SL; Estado de São Paulo: Município de São José dos Campos: small stream tributary of the Rio Santa Bárbara, Rio do Peixe drainage, Rio Paraíba do Sul basin, São Francisco Xavier, Serra dos Poncianos, part of the Serra da Mantiqueira; 22 ° 51 ' 47 " S, 45 ° 54 ' 60 " W; about 980 m asl; 21 April 2023; C. R. M. Feltrin, leg.; UFRJ 13674.
Paratypes. (all from Estado de São Paulo: Município de São José do Campos: Rio do Peixe drainage, Rio Paraíba do Sul basin, São Francisco Xavier, Serra dos Poncianos, part of the Serra da Mantiqueira): BRAZIL • 1 ex., 75.6 mm SL (stained with alizarin and partially dissected); collected with holotype; UFRJ 13673; 1 ex., 79.1 mm SL; stream tributary of Rio Santa Bárbara; 22 ° 53 ' 45 " S, 45 ° 56 ' 34 " W; about 765 m asl; same collector and date as holotype; UFRJ 13681; 1 ex., 44.5 mm SL (cleared and stained for osteological analysis); same locality and collector as holotype; 29 October 2023; UFRJ 14201.
Diagnosis.
Trichomycterus antiquus is distinguished from all other species of Paracambeva, except T. itatiayae, by having a relatively large head, its length 20.4–22.8 % SL (vs. 11.4–18.1 % SL), the presence of a deep concavity on the postero-ventral margin of the metapterygoid, accommodating a pronounced expansion of the postero-dorsal quadrate outgrown (Fig. 3 B, see also Costa 2021: fig. 3 B for similar condition in T. itatiayae; vs. metapterygoid concavity, when present, never deep and quadrate expansion, when present, never pronounced in other species of Paracambeva, e. g. Costa et al. 2023 b: figs. 6 G, H) and the presence of a a deep U-shaped concavity on the dorsal margin of the anterior hyomandibular anterior outgrown (Fig. 3 B, see also Costa 2021: fig. 3 B for similar condition in T. itatiayae; vs. concavity, when present, never U-shaped, e. g. Costa et al. 2023 b: figs. 6 G, H). Trichomycterus antiquus differs from T. itatiayae by the presence of the anterior infraorbital canal (vs. absence), jaw teeth sharply pointed (vs. incisiform), a wider body and head (body width 11.9–15.0 vs. 6.2–8.8 % SL; head width 51.8–58.4 vs. 68.7–75.7 % SL), a longer pre-dorsal length (66.0–65.2 vs. 59.2 – 64.0 % SL), a longer pre-pelvic length (60.7 – 65.2 vs. 54.9–56.9 % SL), a deeper head (head depth 51.5–58.4 vs. 39.0–50.8 % SL), a large eye (eye diameter 8.8–11.3 vs. 7.4–8.2 % of the head length), a short sesamoid supraorbital, about twice longer than the lacrimal (Fig. 3 A; vs. long, about four times longer, Costa 2021: fig. 2 B); a well-developed postero-lateral process of the autopalatine (Fig. 3 A; vs. rudimentary, Costa 2021: fig. 2 B); and a slender and long maxilla, longer than premaxilla (Fig. 3 A; vs. relatively deep, shorter than premaxilla, Costa 2021: fig. 2 B).
Description.
General morphology. Morphometric data appear in Table 3. Body relatively deep (Fig. 1 A), greatest body depth at vertical through midway between pectoral and pelvic-fin bases. Trunk subcylindrical to compressed on caudal peduncle, dorsal and ventral lateral profiles weakly convex to almost straight. Whole body, except venter, covered with minute papillae. Small putative axillary gland above pectoral fin, below lateral line, with small orifice just posterior to opercular patch of odontodes (Fig. 2 A). Lateral line of trunk consisting of anterior minute canal with two pores obliquely arranged, posterior followed by almost imperceptible line between humeral region and caudal-fin base with minute superficial neuromasts. Anterior-most pore of lateral line more ventrally positioned than posterior one. Urogenital opening consisting of transverse aperture situated in shallow depression. Anus positioned immediately in front of urogenital opening, at vertical just posterior to dorsal-fin origin.
Head sub-trapezoidal in dorsal view, dorsal surface flat (Fig. 1 B). Eye small, positioned on dorsal head surface, nearer snout tip than posterior margin of opercle. Distance between anterior and posterior nostrils approximately half distance between posterior nostril and orbit. Tip of nasal barbel posteriorly reaching area between orbit and opercular patch of odontodes, tip of maxillary and rictal barbels reaching middle of interopercular patch of odontodes. Mouth subterminal. Jaw teeth pointed, irregularly arranged. Cleared and stained specimen with 48 teeth on premaxilla, 38 on dentary. Odontodes narrow, pointed to sub-incisiform in larger odontodes of larger specimens, about straight, irregularly arranged, 14 or 15 on opercle and 44 or 45 on interopercle. Cephalic latero-sensory system comprising long canal interconnecting supraorbital, posterior section of infraorbital, and postorbital canals, and isolated anterior infraorbital canal. Supraorbital sensory canal with three pores, s 1, s 3, and s 6; anterior section of infraorbital canal with two pores, i 1 and i 3; posterior section of infraorbital canal with two pores, i 10 and i 11; and postorbital canal with two pores, po 1 and po 2. All pores paired. Pore s 6 about equidistant from orbit than its homologous pore.
Fins thin with thick bases and convex free margins (Fig. 1 A). Anal-fin origin at vertical, immediately posterior to middle of dorsal-fin base, at vertical through base of 4 th bifid dorsal-fin ray. First pectoral-fin ray terminating in short filament, its length about 20 % of pectoral-fin length. Pelvic posteriorly overlapping anus and urogenital papilla. Posterior extremity of pelvic fin at vertical through area just anterior to middle of dorsal-fin base. Pelvic-fin bases medially separated by minute interspace. Caudal fin subtruncate. Total dorsal-fin rays 11 (ii + II + 7), total anal-fin rays 9 (ii + II + 5), total pectoral-fin rays 7 (I + 6), total pelvic-fin rays 5 (I + 4), total principal caudal-fin rays 13 (I + 11 + I), total caudal dorsal procurrent rays 15 (xiv + I), total caudal ventral procurrent rays 13 (xii + I).
Osteology (Fig. 3). Mesethmoid slender, T-shaped, anterior margin about straight, cornu narrow, longitudinal main axis gently laterally widening close anterior margin of lateral ethmoid. Lateral ethmoid without lateral projections. Lacrimal thin, not associated to infraorbital canal, separated from sesamoid supraorbital by long interspace. Sesamoid supraorbital short and slender, its length about twice lacrimal length, its width about equal lacrimal width. Premaxilla sub-trapezoidal in dorsal view, slightly tapering laterally. Maxilla slender, boomerang-shaped, slightly longer than premaxilla.
Autopalatine robust, sub-rectangular in dorsal view when excluding postero-lateral process, its largest width about half autopalatine length including anterior cartilage. Lateral margin of autopalatine nearly straight, medial margin concave. Autopalatine posterolateral process well-developed, triangular, its length about equal autopalatine length, excluding anterior cartilage. Metapterygoid subtrapezoidal, deeper than long. Postero-ventral margin of metapterygoid deeply concave, accommodating pronounced dorsal expansion of quadrate. Dorsal extremity of metapterygoid truncate, anterior margin convex, posterior margin about straight. Quadrate L-shaped, with pronounced postero-dorsal outgrowth, anterior margin concave. Hyomandibula moderately long. Anterior hyomandibular outgrowth deep, antero-dorsal margin about horizontal, posteriorly followed by deep U-shaped concavity.
Opercle elongate, slightly longer than interopercle. Dorsal opercular process short and blunt. Opercular articular facet for hyomandibula laterally protected by laminar shield articular facet for preopercle inconspicuous. Opercular odontode patch moderately slender, its width about half length of dorsal hyomandibula articular facet. Interopercle moderate in length, about equal hyomandibular anterior outgrowth length. Anterior margin of interopercle with pronounced anterior projection. Preopercle slender, without distinctive ventral projections.
Parurohyal lateral process relatively short, with blunt extremity, slightly curved posteriorly. Parurohyal head well-developed, with pronounced anterolateral paired process. Middle parurohyal foramen large, longitudinally elongate. Posterior process of parurohyal long, its length about four fifths distance between anterior margin of parurohyal and anterior insertion of posterior process. Branchiostegal rays 8.
Vertebrae 38. Ribs 15. Dorsal-fin origin at vertical through centrum of 21 st vertebra, anal-fin origin at vertical through centrum of 24 th vertebra. Two dorsal hypural plates corresponding to hypurals 3 + 4 + 5; single ventral hypural plate corresponding to hypurals 1 + 2 + parhypural.
Colouration in alcohol.
Flank pale yellow to yellowish white ventrally, with diffuse dark grey stripe along longitudinal midline, widening and breaking into small spots posteriorly. Great concentration of small dark grey spots on dorsal portion of flank, no or few similar spots on ventral portion. Dorsal surface of trunk and head pale brown, with small, faint grey spots, ventral surface white. Nasal and maxillary barbels pale brown, rictal barbel white. Fins hyaline, with whitish bases. In specimen UFRJ 13681, longitudinal stripe broader and darker, brown spots on dorsum, dorsal, and ventral portions of flank.
Etymology.
From the Latin antiquus (old), referring to the relatively old estimated age of the species lineage in the Miocene (see below), when compared with the major species diversification of Paracambeva in the Pliocene.
Distribution.
Trichomycterus antiquus is only known from the upper Rio do Peixe drainage, Rio Paraíba do Sul basin, south-eastern Brazil, at altitudes between about 765 and 980 m asl (Fig. 4).
description: Published as part of Costa, Wilson J. E. M., Feltrin, Caio R. M., Mattos, José Leonardo O. & Katz, Axel M., 2024, A new rare catfish species from southeastern Brazil provides insights into the origins of similar colour patterns in syntopic, distantly related mountain trichomycterines (Siluriformes, Trichomycteridae), pp. 755-767 in Zoosystematics and Evolution 100 (2) on pages 755-767, DOI: 10.3897/zse.100.118000