The tiny arms of Tyrannosaurus rex likely evolved as giant predatory dinosaurs shifted to using their massive skulls and jaws for hunting, according to new research. Scientists examined dozens of theropod species and found a strong connection between shrinking forelimbs and robust skulls. The study suggests this change occurred as predators targeted enormous prey.
Researchers from University College London and the University of Cambridge analyzed 82 theropod species. They determined that reduced forelimbs evolved independently in at least five lineages, including tyrannosaurids. The link between short arms and strong skulls proved stronger than any connection to overall body size.