Who was eating aetosaurs?

Desmatosuchus encounters Postosuchus. Artwork by Douglas Henderson in Dawn of the Dinosaurs: Life in the Triassic by Nicholas Fraser (Plate 7.5A)

Postosuchus is often depicted preying on aetosaurs, but how do we know that this we really the case? With their heavy armor, aetosaurs were likely a very difficult animal to take down. Once the aetosaur was dead, it would still be fairly difficult to get around that armor, which covered the back, neck, tail, and abdomen.

However, the discovery of a particular aetosaur osteoderm from Petrified Forest National Park may be able to add some weight to our assumptions that Postosuchus was preying on aetosaurs. The osteoderm belonged to Typothorax, a medium sized aetosaur living in the Late Triassic of Arizona. Bite-marks cover the osteoderm, but the most striking evidence lies on the underside of the armored plate. Four perfect punctures, formed from a single bite, adorn the smooth ventral surface. All the evidence points towards a large predator like Postosuchus, and the bite matches perfectly with the front teeth of Postosuchus kirkpatricki.

So, who was eating aetosaurs? It looks like Doug Henderson and other paleoartists were right. Postosuchus was a daunting top predator in the Triassic of North America and we can now say that this large rauisuchid had equally daunting prey.