Niobichthys Schaefer, Provenzano, 1998

Genus Niobichthys Schaefer, Provenzano, 1998 View in CoL

Niobichthys Schaefer, Provenzano, 1998: 222 View in CoL .

Type-species: Niobichthys ferrarisi Schaefer, Provenzano, 1998 View in CoL . Type by original designation. Gender masculine.

Included species. Niobichthys ferrarisi Schaefer, Provenzano, 1998 View in CoL .

Diagnosis. Niobichthys is diagnosed based on four nonexclusive autapomorphies: serrations on inner margin of pectoral-fin spine present and oblique (char. 51.1); anterior portion of basipterygium open, bearing pair of fenestrae (char. 60.0); snout tip covered by naked area (char. 63.1); and path of preopercle-mandibular branch of laterosenory canal passes from pterotic to fifth infraorbital (char. 74.1).

Comparisons. The only species of Niobichthys is distinguished from other hypoptopomatins by the absence of a rostral plate, leaving a naked area in the snout tip ( vs. rostral plate present), and by possession of conical, unicuspid accessory teeth in both the premaxilla and dentary ( vs. accessory teeth absent). Niobichthys also differs from Hypoptopoma , Nannoptopoma , Otocinclus , Leptotocinclus , and Nannoxyropsis by having a strongly depressed, elongated and narrow caudal peduncle ( vs. caudal peduncle not depressed). Additionally, Niobichthys is distinguished from Oxyropsis by the dorsolateral position of the eyes, which are not visible in ventral view ( vs. eyes visible in ventral view), and by possession of precleithral plates ( vs. precleithral plates absent). From Acestridium , Niobichthys is further distinguished by lacking the spatulate snout projection, by 14 branched rays in the caudal-fin ( vs. 10 or 12 branched rays); by the lateral-line canal that shifts to the dorsal series of lateral plates after truncation of the median plate series ( vs. shifting to the ventral series); and by odontodes on the dorsal surface of the pectoral-fin spine that are arranged in two or three rows ( vs. odontodes randomly arranged).