Herrerasaurus was among the earliest known dinosaurs. Its fossilized remains have been found in the Late Triassic (ca. 230 Ma) Ischigualasto Formation of northwest Argentina. While this area is tremendously arid today, fossils reaveal that the Triassic landscape was forested and recieved strong seasonal rainfall. Whith its sharp teeth and bipedal posture Herrerasaurus was probably an active predator that hunted small animals and may have been related to later theropod dinosaurs including Tyrannosaurus rex and even modern birds. Partially healed bite marks on this skull suggest that this individual survived at least one attack, either from a larger predator or perhaps from a rival Herrerasaurus.