Staurikosaurus is a species of dinosaurs.

Discovery

There exists only a solitary specimen of Staurikosaurus ("Lizard of the Southern Cross"), improved from the Santa Maria formation in Rio Grande de Sul, southern Brazil. The name refers to the star constellation "The Southern Cross", only able to be seen in the southern hemisphere - when Staurikosaurus was found in 1970, it was unusual to find dinosaurs in the southern hemisphere. It was first described by Edwin H. Colbert, operational at the American Museum of Natural History.

Description

Staurikosaurus was a little theropod from the Middle Triassic, 231 to 225 million years ago - specifically the Carnian age. It is one of the first dinosaurs that are known. At just two meters in length, 80 cm tall and weighing just thirty kilograms, Staurikosaurus was tiny in contrast to later theropods like Megalosaurus. Although its teeth and posture suggest it was a carnivore, some paleontologists favor to classify Staurikosaurus as a sauropod like the later Diplodocus due to its prosauropod-like skeleton. It seems to stand for a transition period as one of these sub-orders evolved from the other. However, one more fossil (as yet unnamed) was found in 1984 in Arizona's Painted Desert that was such a characteristic prosauropod that it seems that the group evolved before Staurikosaurus. Newer research seems to corroborate that Staurikosaurus and the related Eoraptor and Herrerasaurus are definite theropods and evolved after the sauropod line had tear from theropoda.

There exists much unfinished fossil record of Staurikosaurus, consisting most of the spine, the legs and the large lower jaw. However, dating from such an near the beginning period in the dinosaurs' history and being otherwise so primitive, most of Staurikosaurus' other features as being prehistoric also can be reconstructed. For example, Staurikosaurus is usually depicted with five toes and five fingers - very simple features of an unspecialized dinosaur. However, since the skeletal arrangement of the legs is known, it can be seen that Staurikosaurus was a quick runner for its size. It also had just two vertebrae amalgamation the pelvis to the spine, a distinctly primitive arrangement. The tail would have been long and thin to balance the border - later sauropods had larger, shorter tails family member to their weight.

The recovered mandible suggests that descending joint of the jaw allowed it to move backwards and forwards, as well as up and down. Thus smaller prey could be worked backwards towards Staurikosaurus' throat, the length of its small and backwards-curving teeth. This feature is ordinary in theropods of the time, but disappears in later theropods that most probably had no need for efficiency in eating smaller prey.