Abstract
ABSTRACT A new miniature species of banjo catfish of the genus Hoplomyzon is described from the Lake Maracaibo Basin in Venezuela. The new species is distinguished from all its congeners by the straight anterior margin of the mesethmoid (vs. a medial notch); a smooth and straight ventral surface of the premaxilla (vs. presence of bony knobs on the ventral surface of premaxilla); absence of teeth on dentary (vs. teeth present on dentary); configuration of ventral vertebral processes anterior to anal fin, which are composed of single processes anterior to anal-fin pterygiophore (vs. paired process); presence of several filamentous barbel-like structures on the ventral surface of head of adults (vs. small papillous structures in the ventral surface of head of adults); and 8 anal-fin rays (vs. 6 or 7). An extensive osteological description is made of the holotype using high-resolution x-ray computed microtomography (HRXCT).
Highlights
Hoplomyzon Myers, 1942 is a member of the aspredinid tribe Hoplomyzontini, a small and peculiar group of armored banjo catfishes of small body sizes and distinctive, specialized morphologies (Stewart, 1985)
The Caño raya at type locality is a medium size stream (~12m wide) with mostly slow flowing white waters running over sand intercalated with riffles of fast flowing waters over pebbles; little marginal and floating vegetation
Hoplomyzon cardosoi is named in honor and memory of a dear colleague who prematurely passed away, Alexandre Rodrigues Cardoso, for his humbleness, positive attitude, and dedicated friendship, and for his contributions to the taxonomy of Neotropical fishes, including the family Aspredinidae
Summary
Hoplomyzon Myers, 1942 is a member of the aspredinid tribe Hoplomyzontini, a small and peculiar group of armored banjo catfishes of small body sizes and distinctive, specialized morphologies (Stewart, 1985). Friel (1994), in a phylogenetic analysis of the family Aspredinidae, diagnosed Hoplomyzon from other aspredinid genera by having two bony knobs on ventral surface of premaxilla, superficially covered by fleshy papillae, dorsal and ventral plates not overlapping adjacent ones, two or three sets of paired pre-anal-fin plates, a maxillary barbel adnate to head by membrane, and a short pectoral-fin spine (less than 25% SL) Of these characters, only the presence of premaxillary knobs on ventral surface of the premaxilla was recovered as an unambiguous synapomorphy (Friel, 1994), other diagnostic features ambiguous within Hoplomyzontini. The tribe Hoplomyzontini is perhaps the most well supported group of Aspredinidae with 27 unambiguous morphological synapomorphies (see Friel, 1994: 91) reflecting its specialized and unique morphology
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