What specific feature defines the genus Xenotarsosaurus regarding its lower leg?
The unique configuration of its tarsal bones
The defining characteristic that warrants the specific designation of *Xenotarsosaurus* is the structure and articulation of its tarsals, which are the ankle bones. While many theropods exhibit flexible ankles, the configuration found in this Patagonian dinosaur was notably distinct. Paleontologists focused on this specific arrangement—whether through unique bone shape, contact pattern, or subtle fusion—as the key diagnostic trait. This variation in the tarsals suggests a potentially specialized gait or method of weight distribution that evolved uniquely in this lineage, distinguishing it from other coexisting meat-eaters. This anatomical detail is central to understanding its place within dinosaur evolution.
