Staurikosaurus
Staurikosaurus (Pronounced "STORE-ee-koh-SAWR-us", "Southern Cross lizard") is a genus of herrerasaurid[1] dinosaur from the Late Triassic of Brazil, found in the Santa Maria Formation.
Colbert (1970) described Staurikosaurus as a small and agile, bipedal predator.[2] Staurikosaurus lived during the late-Carnian and early-Norian stage, of the Late Triassic, approximately 225 million years ago—which makes it one of the earliest dinosaurs known. At 2.25 metres (7 ft 5 in) long,[3] 80 centimetres (31 in) tall, and weighing 30 kilograms (66 lb), Staurikosaurus was small in comparison to later theropods like Megalosaurus. The type specimen has long but relatively slender limb bones.
There exists a very incomplete fossil record of Staurikosaurus, consisting of most of the spine, the legs and the large lower jaw. However, dating from such an early period in the dinosaurs' history and being otherwise so primitive, most of Staurikosaurus' other features as being primitive also can be reconstructed. For example, Staurikosaurus is usually depicted with five toes and five fingers[4]—very simple features of an unspecialized dinosaur. However, since the skeletal structure of the legs is known, it can be seen that Staurikosaurus was a quick runner for its size. It also had just two vertebrae joining the pelvis to the spine, a distinctly primitive condition.
The available teeth for Staurikosaurus bear a morphology that strongly suggests a carnivorous diet. The teeth are all serrated, laterally compressed, and caudally curved (i.e. the top of each tooth is curved back toward the throat).[5] This dentition suggests that Staurikosaurus could catch and hold prey, as well as slice and tear flesh to aid in mechanical digestion.[6]
The tail of Staurikosaurus was relatively long (with more than 40 vertebrae) compared to the rest of its body and was held straight and off the ground as it ran. The rear part of Staurikosaurus's tail is stiffened by features of the tail vertebrae. Ostrom (1969a) considered this adaptation to serve as a dynamic stabilizer facilitating the animal's leaping and running.[7]
