Compared to Tyrannosaurids, what characterizes the forelimbs of Abelisaurids like *Xenotarsosaurus*?

Extremely reduced, sometimes even more diminutive than those of tyrannosaurids.

One of the stark comparative differences between the northern Tyrannosauridae and the southern Abelisauridae lineage, which includes *Xenotarsosaurus*, is the size and robustness of the forelimbs. While tyrannosaurids possessed forelimbs that were certainly reduced when compared to their massive body size, abelisaurids often exhibited forelimbs that were even more severely reduced, sometimes described as being vestigial in comparison. This shared evolutionary trait of reducing forelimb size—though taken to an extreme in some abelisaurids—is cited as an example of parallel evolution driven by specialization focusing power into the skull and hindquarters for locomotion and attack.