Protorosaurus speneri

Protorosaurus ("first lizard") is a genus of lizard-like early archosauromorph reptiles. Members of the genus lived during the late Permian period in Germany and Brazil. Once believed to have been an ancestor to lizards, Protorosaurus is now known to be one of the oldest members of the lineage that would eventually lead to archosaurs such as crocodilians and dinosaurs.

Protorosaurus grew up to 2 metres (6.6 ft) in length, and was a slender, lizard-like animal, with long legs and a long neck. Its body form suggests that it was fast-moving, although it may have fed primarily on insects. Protorosaurus was closely related to Czatkowiella from the Early Triassic of Poland.

In 1914, a new ceratopsian dinosaur found by Lawrence Lambe was again given the name Protorosaurus (in this sense meaning "before Torosaurus"). When Lambe found that the name had already been used for the early archosauromorph, he renamed his ceratopsian Chasmosaurus.

In Geopark of Paleorrota, Rio Grande do Sul, Brazil, 3 vertebrae and some bones of the animal were found.