Multiple outlets report a new study that offers an evolutionary explanation for why Tyrannosaurus rex has disproportionately small arms. The research links arm size to how predatory adaptations developed as dinosaurs diversified and plant-eating groups became larger. According to The Independent, the study finds that the robustness of tyrannosaur skulls—associated with biting and feeding—begins evolving first, as predators respond to changes in their prey. This timing is described as following soon after dinosaurs become dominant land animals. Popular Science frames the finding around an “use it or lose it” idea: traits that are less used may not be strongly maintained over evolutionary time. Other coverage also highlights a University College London connection and suggests the explanation may relate to T. rex’s “giant head,” emphasizing the shift toward feeding and attack capabilities centered on the skull rather than the forelimbs. Across reports, the central claim is that T. rex’s small arms are not treated as a mystery without context, but as a predictable outcome of how major feeding features evolved during the rise of larger herbivorous dinosaurs.