According to the artistic interpretation of much of the paleo-artist community, Aucasaurus ate nothing but baby Titanosaurs. The small morsels would have been easier to eat for a dinosaur with a posterior facing forelimb that was not much help in grabbing and holding prey. Despite the longer, but shallower and possibly weaker jaw, in comparison with Carnotaurus, Aucasaurus was probably capable of bringing down larger prey than an infant Titanosaur. Adult Titanosaur was probably a difficult meal to acquire for a solitary animal, but it was most likely on the menu at any life stage; it may have required a lot more effort as a larger animal to a certain point with old age lowering the effort put in by these Abelisaurid hunters.
The forelimb of Aucasaurus is not as reduced as it appears in this series of illustrations. The very bird-like appearance of the hindlimbs is rather interesting for sure; the scaled foot and an almost booted tarsus look to the leg itself allows for a rather interesting interpretation of the fossil animal. The neck is elongate and the snout is a little shorter than we anticipate from the fossils. The representation here is presented not for analysis, but mostly because the body shape is well defined and appropriately expressed and therefore represents fairly well what this dinosaur would have looked like in life.