Tyrannosaurid Skeletal Design First Evolved at Small Body Size

Abstract

Diddy Dinosaurs Tyrannosaurs were the dominant large dinosaur predator during the Late Cretaceous. They have several distinct specialized features, including an oversized skull, huge hindlimbs, and tiny arms, that have been thought to have evolved in concert with their large size and carnivorous diet. Sereno et al. (p. 418 , published online 17 September; see the Perspective by Clark ) now describe an earlier, diminutive tyrannosaur from China that also has these common specializations. Thus, these features were not a result of size increase but appear to have been required for feeding efficiency at all sizes.