What is "hyposaurus"

Hyposaurus is a genus of extinct marine dyrosaurid crocodyliform. Fossils have been found in Paleocene aged rocks of the Maria Farinha Formation in Pernambuco, Brazil, Iullemmeden Basin in West Africa, ? Campanian– Maastrichtian (Late Cretaceous) Shendi Formation of Sudan and Maastrichtian (Late Cretaceous) through Danian (Early Paleocene) strata in New Jersey, Alabama and South Carolina. Isolated teeth comparable to Hyposaurus have also been found in Thanetian (Late Paleocene) strata of Virginia. It was related to Dyrosaurus, and is the only dyrosaurid known from the western hemisphere.

The priority of the species H. rogersii has been debated, however there is no sound basis for the recognition of more than one species from North America. The other North American species (i.e. H. fraterculus, H. ferox and H. natator) are therefore considered nomina vanum (i.e. empty names).