Ignotosaurus is an extinct genus of silesaurid dinosauriform known from the Late Triassic (Carnian) Cancha de Bochas Member of the Ischigualasto Formation in the Ischigualasto-Villa Unión Basin in northwestern Argentina.

The acetabulum has a back wall created by a ventral flange and this closes a socket as it is in contact with the ischium and pubis.

A ridge rises from the dorsal edge of this crest and joins the preacetabular process, as in the close relative Silesaurus.

The preacteabular process is flattened anteroposteriorly and is angled at 90° to the iliac blade, pointing anterolaterally - these are the diagnostic features of this species.

As Ignotosaurus was probably a herbivore, like other silesaurids, it would probably have flourished here, competing for food with rhynchosaurs, cynodonts and possibly some early dinosaurs.