Tawa's skeleton also shares many features with Herrerasaurus and other primitive dinosaurs, and so it helps paleontologists classify those earlier creatures as true theropods.
Known from a single buck-toothed skull, Daemonosaurus has relatively large bones at the tips of its jaws, as Herrerasaurus did, mixed with the vertebral air sacs that generally characterize later dinosaurs.
Among the creatures on display are representatives of every major dinosaur group, including Grallator, the fossilized footsteps of an early dinosaur known only by its footprints, along with a cast of one of the earliest known dinosaurs, the meat-eater Herrerasaurus
. From the group of armored dinosaurs come the thyreophorans: fossilized bones of an Ankylosaur and a cast of Stegosaurus.
New information on the systematics and post-cranial skeleton of Herrerasaurus ischigualastensis (Theropoda: Herrerasauridae) from the Ischigualasto Formation (Upper Triassic) of Argentina.
The pectoral girdle and forelimb of the basal theropod Herrerasaurus ischigualastensis.
Student Ricardo Martinez found the fossilized Eoraptor less than a mile from the place where, in 1988, Sereno discovered a nearly complete skeleton of the oldest known dinosaur, Herrerasaurus. "As the students were walking away from a less interesting specimen, Ricardo happened to pick up the skull, which was lying on the ground, covered in rubble," Sereno explains.
However, some of the fossil characteristics place Eoraptor as an early member of the "theropod" group of dinosaurs, a branch that includes Herrerasaurus and Tyrannosaurus.
In 1988, the young University of Chicago paleontologist traveled to the beautiful Valley of the Moon in the foothills of the Andes and returned with the best-preserved fossil ever found of Herrerasaurus, the oldest and most primitive dinosaur then known.
Along with Herrerasaurus, the new find is also offering insight into how dinosaurs rose from humble beginnings to reign over the continents for a staggering 150 million years.
The Eoraptor and Herrerasaurus skeletons found by Sereno and his colleagues come from the Ischigualasto Provincial Park in northwestern Argentina.
Even Herrerasaurus, a contemporary of the 225-million-year-old Eoraptor, seems specialized in comparison.
Among other finds, the group discovered several important pieces of the primitive dinosaur Herrerasaurus
. Previously, scientists had only some vertebrae, a pelvis and a hind limb from the animal.