Odontogriphus omalus

Odontogriphus (from , 'tooth' and , 'riddle') is a genus of soft-bodied animals known from middle Cambrian Lagerstätte. Reaching as much as in length, Odontogriphus is a flat, oval bilaterian which apparently had a single muscular foot and a "shell" on its back that was moderately rigid but of a material unsuited to fossilization.

Originally it was known from only one specimen, but 189 new finds in the years immediately preceding 2006 made a detailed description possible. (221 specimens of Odontogriphus are known from the Greater Phyllopod bed, where they comprise 0.42% of the community.) As a result, Odontogriphus has become prominent in the debate that has gone on since 1990 about the evolutionary origins of molluscs, annelid worms and brachiopods. It is thought that Odontogriphuss feeding apparatus, which is "nearly identical" to Wiwaxias, is an early version of the molluscan radula, a chitinous "tongue" that bears multiple rows of rasping teeth. Hence Odontogriphus and Wiwaxia are often classified as closely related to true molluscs.