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
Previously, radioisotope dating has shown the oldest known dinosaurs, Herrerasaurus
and its contemporaries to be just under 228 million years old.
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.
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.
Sereno revisited the same sculpted badlands in 1991 and came home with a new type of dinosaur even more basic in its anatomy than Herrerasaurus.
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.
Among other finds, the group discovered several important pieces of the primitive dinosaur Herrerasaurus