Anchisaurus polyzelus

A surprisingly lightly built sauropodomorph from the Early Jurassic of eastern North America, Anchisaurus was one of the first dinosaurs to be scientifically described from the United States. Although traditionally thought to be quite a basal member of the early, two-legged sauropod relatives, more recent studies suggest it was quite a bit closer to the origin of sauropods, despite being modest in size and lightly built.