Brachyhypopomus bullocki, a new species of electric knifefish (Gymnotiformes: Hypopomidae) from northern South America

We describe the new species Brachyhypopomus bullocki (Gymnotiformes: Hypopomidae) from the rio Orinoco basin of Colombia and Venezuela as well as the Takutu River/rio Branco-rio Negro basin of Guyana and Brazil. Among its congeners, B. bullocki most closely resembles Brachyhypopomus brevirostris (Steindachner, 1868) in possessing an elongated caudal filament which may reach up to 45% TL in reproductive males, in having wide, evenly spaced saddles of pigment over the dorsum connecting to lateral bands of pigment along the abdominal Hanks, and in having a mesocoracoid bone. This new species is distinguished from B. brevirostris and other members of the genus by a large eye (15.5-19.2% of head length), a short abdomen usually with 12 pre-caudal vertebrae, and poorly ossified third and fourth branchiostegal rays that are enlarged distally, producing a bulbous appearance of the opercular region. The electric organ discharge waveform of B. bullocki is biphasic, 0.9-1.6 milliseconds in duration, and the pulse rate varies from 20-80 Hz.