Tyrannosaurs Revisited Tyrannosaurs represent some of the most successful and largest carnivores in Earth's history. An expanding fossil record has allowed studies of their evolution and behavior that now allow broader comparisons with other groups, not just dinosaurs. Brusatte et al. (p. 1481 ) review the biology and evolutionary history of tyrannosaurs and update their phylogenetic relations to include several new fossils. The analysis suggests that tyrannosaurs remained relatively small (less than about 5 meters long) until the Late Cretaceous (about 80 million years ago).