Biotoecus Eigenmann and Kennedy (Teleostei: Cichlidae): description of a new species from the Orinoco basin and revised generic diagnosis

Abstract

Biotoecus dicentrarchus n.sp. is described from the upper and middle Rio Orinoco drainage in Colombia and Venezuela. The species is distinguished from all other cichlids by having only two anal fin spines and from its sole congener, the Amazonian Biotoecus opercularis (Steindachner), also by dorsal fin shape and count, colour pattern, more reduced dentary lateralis canal and lack of anguloarticular lateralis canal. A revised diagnosis of Biotoecus includes: (1) lack of interhypohyal ligament, (2) reduced lateral line system involving three instead of more lacrimal foramina, loss of infraorbital ossicles, fragmentary dentary canal, loss of distal extrascapular, flank lateral lines with pored instead of tubed scales except occasionally the first scale in the upper lateral line, loss of accessory caudal fin lateral lines, (3) long instead of short or diffuse anteromedial palatovomerine ligament, (4) extraordinarily long caudal peduncle (23·3–26·3% of SL) containing 9 vertebrae, and (5) dorsal fin count VII–IX. 13–16. Biotoecus has been considered a geophagine cichlid group because of its first gill arch morphology; it is shown here that the crucial structure is only superficially similar in Biotoecus and true geophagines.

Keywords :

• Amazon River
• Biotoecus dicentrarchus
• Biotoecus opercularis
• Colombia
• New Species
• Osteology
• Venezuela