Tyrannosaurinae, Osborn, 1906

Holtz, TR jr., 2004, Tyrannosauroidea, The Dinosauria, University of California Press, pp. 111-136 : 1

Tyrannosaurinae ,

originally named by Osborn (1906), is a clade consisting of Daspletosaurus , Tarbosaurus , and Tyrannosaurus (and possibly Alioramus ), based on the following derived features: the extent of the ventral curvature of the maxilla at least the length of the crown of the tallest premaxillary teeth; the promaxillary fenestra oriented rostrally; the maxillary fenestra expanded, one-half to two-thirds of the area of the eyeballbearing portion of the orbit; the cranial margin of the maxillary fenestra terminating along the cranial margin of the antorbital fossa; the internal antorbital fenestra as tall as or taller than it is long; the caudal portion of the nasals pinched between the lacrimals, the thinnest point approximately half the transverse width of the thickest point or less; the margin of the external antorbital fenestra on the craniolateral surface of the descending ramus of the lacrimal flattening out and not continued on the surface of the jugal; the palatine foramen on the dorsal surface of the palatine recess large; the ectopterygoid internal sinus enlarged, resulting in an inflated appearance of the ectopterygoid body; the midcervical centra less than half as long as the height of the vertical face (the neck much shorter than the dorsal series); craniocaudal length of the ilium greater than the femoral length; and the pubic boot greater than 60% as long as the pubic shaft. Brochu (2002) cautions that at least some of these features might be allometric, and consequently these apparent synapomorphies might simply be the result of any reaching comparable body size in tyrannosaurids. Currie (2003a) has demonstrated that for most of these attributes juvenile albertosaurines and tyrannosaurines have identical proportions, but among larger individuals of the same body size the morphology of the two clades diverges. This suggests an origin of Tyrannosaurinae through hypermorphosis (exaggeration of, and addition to, adult features found in the ancestral condition).

The two North American tyrannosaurines have a more widespread geographic distribution than do the albertosaurine species, ranging from Canada to the American Southwest (Carr and Williamson 2000).