Tyrannosaurid skeletal design first evolved at small body size.
Nearly all of the large-bodied predators (>2.5 tons) on northern continents during the Late Cretaceous were tyrannosaurid dinosaurs. We show that their most conspicuous functional specializations--a proportionately large skull, incisiform premaxillary teeth, expanded jaw-closing musculature, diminutive forelimbs, and hindlimbs with cursorial proportions--were present in a new, small-bodied, basal tyrannosauroid from Lower Cretaceous rocks in northeastern China. These specializations, which were later scaled up in Late Cretaceous tyrannosaurids with body masses approaching 100 times greater, drove the most dominant radiation of macropredators of the Mesozoic.
Sereno
Paul C
PC
Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL 60637, USA. dinosaur@uchicago.edu
Tan
Lin
L
Brusatte
Stephen L
SL
Kriegstein
Henry J
HJ
Zhao
Xijin
X
Cloward
Karen
K
D000818:Animals; D005075:Biological Evolution; D049628:Body Size; D001842:Bone and Bones / Q000033:anatomy & histology*; D054022:Cerebrum / Q000033:anatomy & histology; D002681:China; D025061:Dinosaurs / Q000033:anatomy & histology / Q000145:classification; D005552:Forelimb / Q000033:anatomy & histology; D005580:Fossils; D006614:Hindlimb / Q000033:anatomy & histology; D010802:Phylogeny; D012863:Skeleton; D012886:Skull / Q000033:anatomy & histology; D014070:Tooth / Q000033:anatomy & histology