Tyrannosaurus Rex Ancestry: Origin in Asia, Migration to North America

A new study suggests the Tyrannosaurus rex [ty-ran-uh-sawr-us rex] evolved in North America. However, its direct ancestor came from Asia. This migration occurred via a land bridge connecting the continents over 70 million years ago. The research, led by UCL (University College London) [yoo-see-el] and published in Royal Society Open Science, reveals more. The rapid growth of tyrannosaurids [ty-ran-uh-sawr-idz] (including the T. rex) and megaraptors [meg-uh-rap-tors] coincided with a global cooling period. This followed a peak in temperatures 92 million years ago. This suggests the T. rex and its relatives adapted better to colder climates. This adaptation may be due to their plumage or a more warm-blooded physiology. The team used mathematical models based on fossils, dinosaur evolutionary trees, geography, and climate to explore how tyrannosaurids and megaraptors moved across the world.