A long-hidden species of Pimelodella (Siluriformes: Heptapteridae) from the upper and middle Orinoco, and western Amazon tributaries

Abstract

A new species of Pimelodella is described from the upper and middle basin of the Orinoco River, upper basin of Negro River, and upper basin of the Apaporis River. The new species is distinguished from its congeners by its unique dark saddle on the predorsal region, and also by its maxillary barbel reaching or slightly exceeding the adipose-fin insertion; anterior margin of pectoral fin-spine with minute straight dentitions covering the middle third of the spine, serrae along its distal third, and posterior margin with 8–10 retrorse dentitions along 40–45% of the middle section of the spine; adipose fin short (23.5–27.2% of SL); caudal fin lobes subequal; 38 total vertebrae; and diffuse dark band along the sub-distal region of the dorsal fin. Polymorphism of fusion pattern of the epiphyseal branches of the supraorbital sensory canals is reported for the new species, and its Negro-Orinoco biogeographic pattern is discussed.