TYRANNOSAURINAE (Osborn, 1906), Osborn, 1906

Paul, G. S., 1988, Predatory Dinosaurs of the World, Predatory Dinosaurs of the World, New York: Touchstone Books, pp. 323-349 : 325-326

SUBFAMILY TYRANNOSAURINAE (Osborn, 1906)

Allosaur-like Indosuchus and knobby-nosed Alioramus are rather odd, but the rest of the tyrannosaur genera and species are distinctly uniform. Still a few distinctive characters, including size, robustness, and features of the skull mark these genera and species. Generally, at 2500-to-10,000 +-kg Tyrannosaurus is bigger, more robust (even when similar in size), bigger-toothed, deeper-jawed, and shorter-snouted than 500-to-2500-kg Albertosaurus . The two groups are further distinguished by the way they evolved. Big albertosaurs appear to have become increasingly more gracile, while remaining about the same size. Tyrannosaurus became ever larger and more robust with time. At the same time the two clades parallel one another. For example, both independently develop a bony process in the orbit, and both reduce their forelimbs with time.

Other tyrannosaur taxa have been described, but most are dubious. Philip Currie believes that some teeth and other bones suggest that a new, small gracile tyrannosaur was present in the Judith River Formation. There is also, from what I have seen of it, what appears to be a gracile late Late Cretaceous albertosaur newly found in Alabama.