Based upon the skeletal reconstruction available online. [link]
The protofeathers have been added assuming that the integumentary structures found in ornithischians are homologous to that of saurischians, making “feathers” a synapomorphy of the clade “Dinosauria”, if not Ornithodira (assuming the structures of pterosaurs are homologous too).
This was entirely made on Adobe Photoshop CS4, in order to try an experiment: to see if I was capable of drawing a “close enough” dinosaur only by digital means.
It has proven to be a quick way to draw, though I still prefer the results of combining freehand pencil drawing and coloring in Photoshop.
A simple diagram demonstrating the differences in Saurischian and Ornithischian hips. A.Eoraptor, an early Saurischian; note the forward-pointing pubis B.Lesothosaurus, a primitive Ornithischian; note the reversed pubis C. Staurikosaurus (Saurischian) pelvis D.Lesothosaurus pelvis
Known from a single fossil specimen found in South America in 1970, Staurikosaurus is one of the earliest dinosaurs, the immediate descendants of the two-legged archosaurs of the early Triassic period. Unlike its slightly bigger South American cousin, Herrerasaurus, it seems that Staurikosaurus was a true theropod–that is, it evolved after the ancient split between ornithischian and saurischian dinosaurs.
One odd feature about Staurikosaurus was a joint in its lower jaw that seemed to allow it to chew its food backwards and forwards, as well as up and down. Since later theropods didn’t have this adaptation, it’s likely that Staurikosaurus lived in an stark environment that forced it to extract the maximum nutrition from its wriggling meals.