Dinosaurs were primitively "bipedal": their probable ancestors were small bipedal Archosaurs. The date of the early dinosaur genus "Eoraptor" at 231.4 million years ago is important. "Eoraptor" probably resembles the common ancestor of all dinosaurs; its traits suggest that the first dinosaurs were small, bipedal predators. The discovery of primitive, pre-dinosaur, types in Middle Triassic strata supports this view. Analysis of their fossils suggests that the animals were indeed small, bipedal predators.