Plus: Researchers have discovered a new dinosaur, Eodramaeus, which lived during the dawn of the dinosaur era, about 230 million years ago. The Eodramaeus' fossils were discovered in the Ischigualasto formation in northeastern Argentina, where paleontologists have found other important dinosaur fossils.
Eoraptor, generally considered a theropod as well, is in fact an early ancestor of the sauropod lineage, which includes the giant, long-necked herbivores, the researchers say.
Eodramaeus had more theropod-like features in its skull, such as an opening near the end of the snout called the promaxillary fenestra, as well as other theropod-like features in its trunk pelvis and limbs, the authors report. Eoraptor not only lacked those features but also had more sauropod-like features, including enlarged nostrils and an inset first lower tooth.
Nonetheless, both species were less than 2 meters long and ran on two legs, and these general similarities suggest that the three principal groups of dinosaurs (the ornithischians, the sauropodomorphs and the theropods) did share an overall body plan in the late Triassic, before the dinosaurs rose to dominance in the early Jurassic, according to Dr. Martinez and his colleagues. link
