Plateosaurus (meaning 'flat lizard' - Greek πλατυς/platys "broad" or "flat" from πλατη/platé meaning "flat surface" and σαυρος meaning "lizard") is a genus of plateosaurid prosauropod dinosaur that lived during the Norian and Rhaetian stages of the Late Triassic period, around 216 to 199 million years ago in what is now Europe. There are two actually recognized species, P. engelhardti and P. longiceps, although others have been assigned in the past.
Plateosaurus is the best known of the prosauropods. Dozens of well-preserved skeletons have been unearthed in Triassic sandstones all over western Europe. In some locations, groups of complete individual fossils have been found. Herds travelled together through the Triassic desert landscape of Europe, searching for new feeding grounds. An alternative explanation for the groups of fossils, however, is that solitary individuals inhabited dry, upland areas. When they died, their bodies would have been washed away in periodic flash foods that are typical of desert environments even today. Many individual corpses could have piled up at the end of well-worn flood channels formed at the edge of desert basins.
Plateosaurus were bulky bipedal herbivores that dominated the European arid landscape along with another sauropodomorph dinosaur, Sellosaurus; the earliest known turtle, Proganochelys; and the tiny archosaur Procompsognathus. It had a small skull on a long neck, sharp plant-crushing teeth, powerful limbs, and a large thumb spike on each 'hand' probably used for defence and feeding.