For decades, the reason behind the tiny arms of Tyrannosaurus rex has puzzled scientists. Researchers from University College London believe they have found the answer, linking the evolution of T. rex's small forelimbs to the development of its powerful head and jaws. Their study analyzed 82 species of theropods, revealing that the shortening of arms occurred across various dinosaur groups, including tyrannosaurids and abelisaurids. Surprisingly, this reduction in arm size was not correlated with overall body size but rather with the evolution of strong skulls and jaws. For instance, the Majungasaurus, a smaller predator, also had tiny arms despite weighing significantly less than T. rex. The researchers propose that as prey became larger, T. rex shifted its hunting strategy to rely more on its jaws, making its arms less useful over time. While the study identifies correlations, it emphasizes that the development of robust skulls likely preceded the reduction of forelimbs. This finding challenges previous theories, which suggested various explanations for the tiny arms, including avoiding bites during feeding or aiding in mating behavior.