(Family): Well-developed tail spine present usually. Eye and spiracle on top of head. (Genus): Dorsal fin absent. Caudal fin relatively narrow and long. (Species): Disc roundish and snout pointed. Preocular length 1/3 of disc width. Both sides of disc smooth without spines. Eye small, less than half of spiracle. Small papillae around rim of spiracle. Teeth elliptic and pointed. Tail spine with 14〜19 serrations in one side. Upper surface gray, lower surface whitish. Caudal fin black.
Distribution:
Reported from Venezuela and the mouth of the Amazon.
Remarks:
U. venezuelae, known from Venezuela, is characterized by short snout, preocular length only 1/4 of disc width, and prickly back. (Uyeno and Miyake)