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STL Science Center
27 April 2013
The Completed Incomplete Skeleton
Oscar Alcober, Ricardo Martinez; retrieved from Wikipedia
The amount of skeletal material associated with Staurikosaurus actually fluctuates depending on the source, which is quite odd. Usually some sort of consensus of what skeletal element belongs to what animal gets hashed out eventually amongst scientists. Staurikosaurus, however, is, to my knowledge, composed of only the skeletal elements presented in the anatomical drawing shown above. Paul's latest illustration (via the Princeton Field Guide) shows a substantial amount of skeletal material in addition to this material. I saw no mention by Paul or other sources that cite where this material came from, though I have not done a comprehensive literature search for the week as yet so it may be that in a paper I have yet to review this week that the additional material comes to light. Until then, this is the material that was briefly presented yesterday. As can be seen, it is not extensive, though it is a fair proportion of the skeleton and the basal nature of the remains discovered do allow for some assumptions to be made as to the missing elements and their appearance.
The exact structure of this early dinosaur is a bit "up for grabs" despite the assumptions that can be thrust upon the animal given its basal nature. In a similar image Nobu Tamura illustrates a similar but radically different anatomy for Staurikosaurus. Neither image can be attested to as perfectly correct but they both draw upon the knowledge of the primitive nature of this dinosaur. Dinosaurs of this size were just getting their start in the Triassic and as such were not the apex predators we see in later fossils, but were still quite capable of taking down prey. The manner in which they did so was a little less "dinosaur-like" than when we think of Tyrannosaurs and that sort of large apex predator. Hypothesized to brandish a five fingered hand and foot, these early dinosaurs had small heads and may have had claws that were used more for holding down prey than as killing implements. The Komodo dragon, or maybe even the Green Iguana, may have similar styles of feeding to what Staurikosaurus may have exhibited.
Both the Komodo dragon and Green Iguana both use their forelegs to hold down food items while pulling with their mouths. Staurikosaurus was bipedal as far as we know though, so does this necessarily make sense? The purported five fingers of Staurikosaurus, a body plan shared with the dragons and iguanas, would have enabled the dinosaur to maximize the flesh it held down as its jaws, which would have had to have been fairly strong, tore pieces of flesh from its victims; there is no knowledge as to whether or not Staurikosaurus was primarily a predator or a scavenger and an herbivorous diet is considered unlikely given the theropod body plan (please keep in mind that Therizinosaurs, though theropods, are considered herbivorous).