The type (and only known) species is Inosaurus tedreftensis, described by Albert-Félix de Lapparent in 1960. The specific name is derived from the location of the site, In Tedreft. De Lapparent based the species on a set of remains found in a single location, a number of vertebrae and the top end of a left tibia. They were discovered in a stratum of the Irhazen Group, Berriasian-Barremian. He also indicated four other specimens, all vertebrae found in Niger in the Tegema Group, early Albian, as paratypes. All the specimens are part of the collection of the Muséum national d'histoire naturelle in Paris. Apart from these De Lapparent referred three vertebrae described by Ernst Stromer from Egypt to Inosaurus.
All vertebrae share the same morphology. Despite being from a small animal they are robustly built and very high with enlarged chevron facets and a median groove on the underside.
Inosaurus is today considered a nomen dubium because of the fragmentary nature of the fossils discovered, and because the fossils were recovered from three different locations, leading to worries that this dinosaur is a chimera, based on multiple, perhaps not even closely related, species.