some extent, possibly rooting for food, but were unable to burrow. While features of the limbs indicate that aetosaurs probably dug for food, features of the skull and teeth can indicate what kind of food they were eating. Aetosaurs have many derived features not seen in other crurotarsans, which indicate that they are adapted to a different diet. Unlike the sharp, recurved teeth of other triassic archosaurs, aetosaurs had simple, conical teeth. The tips of the jaws were edentulous, or toothless, and probably supported a beak. The teeth have very little wear, suggesting that aetosaurs did not consume stiff and tough plant material. It is more likely that they consumed non-abrasive vegetation such as soft leaves. Alternative theories have been proposed for the diet of aetosaurs. In 1947, H J Sawin proposed that the aetosaur Longosuchus was a scavenger based on the close proximity of some specimens to a large number of skeletons that were likely carcasses. A 2009 study of the jaw biomechanics of the South American genus Neoaetosauroides suggested that the animal may have fed on larvae and insects without hard exoskeletons. This is because Neoaetosauroides lacks serrations or wear facets on the teeth and has a jaw leverage that is not designed for strong forces such as crushing and chopping. The study recognized that northern aetosaurs such as Desmatosuchus and Stagonolepis did have jaws that would have supported a strong musculature, and were likely better suited to eating plant material. Nests At least some aetosaurs built nests and protected their eggs. In 1996, geologist Stephen Hasiotis discovered 220‑million-year-old, fossilized, bowl-like pits in Arizona's Petrified Forest, in part of the Chinle Formation, assumed to be aetosaur and phytosaur nests. The "nests" are compacted and appear very similar to the nests of the modern day crocodiles who guard their nests. However, it seems that these "nests" are instead the result of sandstone weathering. A second possible aetosaur nest site is known from northeastern Italy. The nests are preserved as depressions in carbonate rock that are circular or horseshoe-shaped, with high ridges around the sides. They appear to be unusually complex for nests created by Triassic reptiles. Archosaur footprints were found nearby that resembled aetosaurs, although they were not present in the same layer. Because the tracks were found so close to the nests, it is likely that aetosaurs built them. Development The ages of individual aetosaurs can be determined