Staurikosaurus

Phylogeny: Dinosauria > Saurischia > Herrerasauria > Herrerasauridae

Overview: Staurikosaurus is one of the oldest known dinosaurs, having lived up to two hundred and thirty-three million years ago, in the Late Triassic. It wasn’t a very large animal, measuring maybe a little over two meters long. It was a carnivore that probably went after mostly smaller prey, though it probably fed upon the kills of other animals in addition to what it could catch itself. Dinosaurs were only just beginning to find their footing during its time, with most of them being similarly small. The largest predator in its local environment would’ve been an animal like Prestosuchus - a member of the clade Pseudosuchia, making it more closely related to modern crocodiles than to dinosaurs. Prestosuchus could grow to be over five meters in length. Predatory dinosaurs wouldn’t fully overtake such animals until after the Triassic-Jurassic extinction. Described in 1970, the generic name of Staurikosaurus refers to the Southern Cross constellation, which is featured on the flag of Brazil, where it was first discovered back in the 1930’s.

Most studies classify Staurikosaurus as a member of the family Herrerasauridae. This made it closely related to dinosaurs like Herrerasaurus and Gnathovorax. Similar to Staurikosaurus, these were mostly smaller predators, though some Herrerasaurus specimens appear to have grown to be decently large (at least by Triassic standards). These creatures had long, rectangular skulls and jaws lined with blade-like teeth. Many of their anatomical traits were very primitive, retaining features later lost among more derived dinosaurs. Originally, herrerasaurids were classified as theropod dinosaurs, but later studies would question this. Herrerasaurids may’ve been closer to the sauropodomorphs (the lineage leading to the long-necked Brontosaurus and its kin), or more likely, were very primitive saurischian dinosaurs outside either the Theropoda or Sauropodomorpha. Some even speculate that Staurikosaurus and its relatives may’ve belonged outside the Dinosauria proper, but this is contested by other researchers.