Brachyhypopomus (Odontohypopomus), Sullivan, John P., Zuanon, Jansen & Cox Fernandes, Cristina, 2013

Sullivan, John P., Zuanon, Jansen & Cox Fernandes, Cristina, 2013, Two new species and a new subgenus of toothed Brachyhypopomus electric knifefishes (Gymnotiformes, Hypopomidae) from the central Amazon and considerations pertaining to the evolution of a monophasic electric organ discharge, ZooKeys 327, pp. 1-34 : 4

Subgenus Odontohypopomus subgen. n.

Type species.

Brachyhypopomus (Odontohypopomus) walteri sp. n.

Included species.

Brachyhypopomus (Odontohypopomus) walteri sp. n., Brachyhypopomus (Odontohypopomus) bennetti sp. n.

Diagnosis. This subgenus of Brachyhypopomus is diagnosed by (1) teeth present on premaxillae: usually one to five small, needle-like teeth on ventral surface of each (Fig. 1); (2) medialmost two branchiostegal rays thin with blades oriented more vertically than remaining three rays; (3) background color in life and to lesser extent in alcohol distinctly yellowish, head and sides peppered with small, widely spaced, dark brown stellate chromatophores that greatly contrast with background color of skin; bands along sides poorly defined, saddles of pigment mostly incomplete over dorsum; (4) a diffuse blotch of subcutaneous pigment directly beneath orbit, suggestive of a teardrop; (5) EOD pulse waveform of very long duration (head-positive phase approx. 2 milliseconds or longer, head-negative phase shorter or absent; Fig. 2) and slow repetition rate (3-16 Hz).

Teeth are absent from the premaxillae in all other rhamphichthyoid species, but present in all other gymnotiform lineages. (The teeth in preserved Odontohypopomus tend to be obscured by overlying tissue and are only easily visible in cleared and stained specimens.) In other Brachyhypopomus , the first (more medial) one or two branchiostegal rays are wide and oriented nearly horizontally, EODs are of shorter duration and faster repetition rates with second head–negative phases nearly equal in amplitude or of greater duration than the head–positive first phase, teardrop-like pigment below the orbit is absent, background color is less yellowish and chromatophores not as dark. In several other Brachyhypopomus species the pigment on the anterior flanks is arranged into distinct bands.

Etymology.

A combination of the Greek word for tooth, odontos, and Hypopomus , type genus of Hypopomidae .