A New Species of Cascudinho of the Genus Hisonotus (Siluriformes: Loricariidae: Hypoptopomatinae) from the Upper Rio Tapajós Basin, Brazil
Hisonotus bockmanni, new species, is described based on specimens collected in a sandbank in the Rio Cururu, a tributary to the Rio Teles Pires, one of the rivers forming the Rio Tapajós in the Amazon Basin. The new taxon is distinguished from its congeners by a unique color pattern, whose most striking features are: two elliptical white spots, anterior to nostrils; predorsal region darkly pigmented with five unpigmented spots arranged as anteriorly pointed chevron; and a rostrocaudally elongate cross along most of the caudal peduncle. The placement of the new species in Hisonotus as well as its possible affinities within that genus are discussed in light of the current knowledge of the phylogenetic relationships among the Hypoptopomatinae.
Hisonotus bockmanni, new species, holotype, LIRP 8139, 21.9 mm SL, female, Brazil, Pará State, Jacareacanga Municipality, sandbank at Rio Cururu, tributary to Rio Teles Pires, tributary to Rio Tapajós, 08°53′42.2″S, 57°14′27.8″W, 140 m asl. (A) Dorsal, (B) lateral, and (C) ventral views.
Hisonotus bockmanni, paratype, LIRP 8140, 23.2 mm SL, female, in lateral view.
Skull of Hisonotus bockmanni, paratype, LIRP 8140, 20.3 mm SL. (A) Dorsal, (B) lateral views. Abbreviations: CL = cleithrum; CP1–CP2 = subocular cheek plates 1 and 2; CPT = compound pterotic; F = frontal; IO1–IO5 = infraorbitals; N = nasal; OP = opercle; PF = prefrontal plate; PN = pre-nasal plates; POP = preopercle; PR1–PR3 = postrostral plates; R = rostral plate; SOC = supraoccipital; SP = sphenotic.
Dorsal view of caudal peduncle of Hisonotus bockmanni, paratype, LIRP 8140, 20.3 mm SL, showing two unpaired platelets at typical adipose-fin position (arrows); numbers are the dorsal plates counting. Anterior to left. (A) Panoramic, (B) detailed views.
Ventral view of pectoral girdle and abdominal platelets of Hisonotus bockmanni, paratype, LIRP 8140, 20.3 mm SL; anterior to top. Note the nude small median area anteriorly is covered by skin. Dotted lines mark the boundaries of pelvic fins. Abbreviations: AP = abdominal plates; CL = cleithrum; CO = coracoid; LAP = lateral abdominal plates.
Ventral view of pelvic girdle of Hisonotus bockmanni, paratype, LIRP 8140, 20.3 mm SL; anterior to top. Abbreviations: APC = anterior process of basipterygium; BPT = basipterygium; LPT = lateropterygium; PPC = posterior process of basipterygium.
Upper Rio Tapajós drainage, showing distribution of Amazonian Hisonotus species: Hisonotus bockmanni (star), Hisonotus chromodontus (square), and Hisonotus luteofrenatus (circle); type localities are black symbols. (1) Rio Tapajós; (2) Rio Teles-Pires; (3) Rio Juruena; (4) Rio Arinos; (5) Rio Cururu.
Suspensorium of Hisonotus bockmanni, paratype, LIRP 8140, 20.3 mm SL. Anterior to left. Abbreviations: AA = compound anguloarticular; CP1–CP2 = subocular cheek plates 1 and 2; D = dentary; HM = hyomandibular; MPT = metapterygoid; MX = maxilla; OP = opercle; PAL = palatine; PALS = palatine splint; PMX = premaxilla; POP = preopercle; Q = quadrate.
Skull of Hisonotus bockmanni, paratype, LIRP 8140, 20.3 mm SL, in lateral view. Dermal plates of dorsal snout anterior to frontals removed. Anterior to left. Abbreviations: CPT = compound pterotic; F = frontal; LE = lateral ethmoid; LPLE = lateral process of lateral ethmoid; ME = mesethmoid; OS = orbitosphenoid; PO = prootic; PS = parasphenoid; PTS = pterosphenoid; SOC = supraoccipital; SP = sphenotic; TVP = transverse process of Weberian complex centra; V = vomer. Arrowhead points to the olfactory nerve foramen.
Contributor Notes
Associate Editor: R. E. Reis.