D1 36; D2 absent; P120; P2 I/5; A 35. Color nearly uniform above and below is blackish or brownish. Head is rather long and flattened. No swim bladder and uses a sucking disc on the top of its head to obtain rides from other animals such as large sharks, and sea turtles. The sucking disk, developed from a transformed spinous dorsal fin. The lower jaw projects past the upper jaw and the teeth, located in jaws and vomer in a villiform patch, are sharply pointed. The scales are small and cycloid.