Rhinotridens, Datovo & Ochoa & Vita & Presti & Ohara & Pinna, 2023

Datovo, Alessio, Ochoa, Luz, Vita, George, Presti, Paulo, Ohara, William M. & Pinna, Mario C. C. de, 2023, A new genus and species of miniature tridentine catfish from the Amazon basin (Siluriformes: Trichomycteridae), Neotropical Ichthyology (e 230076) 21 (3), pp. 1-22 : 4-5

Rhinotridens , new genus urn:lsid:zoobank.org:act:4366BE6C-08F2-4BC1-9FBD-8D0B28E5B540

Type-species. Rhinotridens chromocaudatus , new species.

Diagnosis. Rhinotridens is distinguished from all other tridentine genera by the following unique autapomorphies: presence of a conspicuous anteromedial protuberance on the snout, with a length greater than 35% of its width ( Fig. 1 ; vs. protuberance absent or limited to a discreet convexity with a length less than 18% of its width; see Baskin, 1973: fig. 66; Henschel et al., 2023: figs. 2, 8, 12, 13); set of symphyseal premaxillary and dentary teeth inclined posteromedially ( Fig. 2 ; vs. not inclined, see Azpelicueta, 1990: figs. 2, 3; Henschel et al., 2023: fig. 9); rod-like orbitosphenoid ossified only ventral to the optic nerve ( Fig. 3 ; vs. laminar bone ossified around the optic nerve, with a foramen for its exit, see Baskin, 1973: figs. 28, 29; Henschel et al., 2023: fig. 3); mesethmoid cornua inclined ventrolaterally ( Fig. 4 ; vs. cornua horizontally straight); distal process of the hyomandibula directed anteriorly ( Fig. 5 ; vs. posteriorly, see Baskin, 1973: fig. 51; Henschel et al., 2017: fig. 2g; Henschel et al., 2023: fig. 4); opercular and interopercular odontodophores separated by a large interspace, greater than the depth of the opercular patch ( Fig. 5 ; vs. patches nearly juxtaposed, separated by a distance less than the depth of the opercular patch, see Baskin, 1973: fig. 51; Azpelicueta, 1990: fig. 4; Henschel et al., 2017: fig. 2g; Henschel et al., 2023: fig. 4); and basipterygia fused sagittally ( Fig. 6 ; vs. separated).

Etymology. From rhino, latinized form of the Greek word rhinos (ῥινός), meaning nose or snout, and Tridens , the type genus of the subfamily. In allusion to the rostral protuberance of the new genus. An adjective.

Figures

FIGURE 1. Rhinotridens chromocaudatus, new genus and species, holotype, MZUSP 128216, 17.57 mm SL. Brazil, Amazonas, rio Ipixuna, tributary of the rio Purus, rio Solimões basin. Scale bar = 2.0 mm.

FIGURE 2 | Premaxilla and lower jaw of Rhinotridens chromocaudatus, µCT-scan images, paratype, MZUSP 128217, 16.37 mm SL; A. Dorsal view; B. Ventral view; C. medial view, left side. Symphyseal teeth highlighted in yellow. Ac, angular complex; Dt, dentary; Dth, dentary teeth; Lt, labial teeth; Pmt, premaxillary teeth; Pmx, premaxilla. Scale bar = 0.3 mm.

FIGURE 3 | Cranium, pectoral skeleton, and anterior portion of axial skeleton of Rhinotridens chromocaudatus, µCT-scan images, paratype, MZUSP 128217, 16.37 mm SL; A. Left lateral view; B. Dorsal view. Ac, angular complex; AC, anterior ceratohyal; Ap, autopalatine; Boc, basioccipital; Br, branchiostegal rays; Cl, cleithrum; Dt, dentary; Ep, epioccipital; Fr, frontal; Hy, hyomandibula; Iop, interopercle; Le, lateral ethmoid; Me, mesethmoid; Mx, maxilla; Op, opercle; Osph, orbitosphenoid; Pop, preopercle; Psph, parasphenoid; Psoc, parieto-supraoccipital; Ptr, pectoral-fin rays; Ptscl, postemporosupracleithrum; PC, posterior ceratohyal; Pmx, premaxilla; Pop, preopercle; Pt, pterotic; Pu, parurohyal; Qd, quadrate; Sph, sphenotic-prootic-pterosphenoid; Vh, ventral hypohyal; Vo, vomer; WeC, Weberian capsule. Scale bar = 0.3 mm.

FIGURE 4 | Cranium of Rhinotridens chromocaudatus, µCT-scan images, paratype, MZUSP 128217, 16.37 mm SL; anterior view; arrow indicates right mesethmoid cornu. AC, anterior ceratohyal; Ap, autopalatine; Boc, basioccipital; Br, branchiostegal rays; Dth, dentary teeth; FPV, first post-Weberian vertebrae; Fr, frontal; Hy, hyomandibula; Iop, interopercle; Lt, labial teeth; Me, mesethmoid; Mx, maxilla; Op, opercle; Pop, preopercle; Psoc, parieto-supraoccipital; PC, posterior ceratohyal; Pmx, premaxilla; Pop, preopercle; Pu, parurohyal; Sph, sphenotic-prootic-pterosphenoid; SPV, second post-Weberian vertebrae; Vh, ventral hypohyal. Scale bar = 0.25 mm.

FIGURE 5 | Suspensorium and opercular series of Rhinotridens chromocaudatus, left side, µCT-scan images, paratype, MZUSP 128217, 16.37 mm SL; A. Lateral view; B. Medial view; arrow indicates distal process of hyomandibula. Hy, hyomandibular; Iop, interopercle; Op, opercle; Pop, preopercle; Qd, quadrate. Scale bar = 0.2 mm.

FIGURE 6 | Pelvic girdle of Rhinotridens chromocaudatus, digital illustration of c&s specimen, ventral view, paratype, MZUSP 128217, 16.72 mm SL. Bpt, basipterygium. Scale bar = 0.15 mm.