Daspletosaurus torosus Russell 1970

Figs. 2G, 5F

Diagnosis: (Cranial) Premaxilla does not contact nasals under external nares; lacrymal horn well developed; postorbital rugose, although less that Tyrannosaurus; pro-maxillary fenestra very small; surangular foramen very large. (Postcranial) Postacetabular blade of ilium very long; ischium straight; scapula broadens gradually posteriorly; acromion process of scapula forms a continuous arc with the coracoid.

Stratigraphic and Palaeobiogeographic Distribution: Judith River and Horseshoe Canyon formations of Alberta,Canada;Judith River Formation of Montana.

Discussion: As Russell (1970) has pointed out, adult Daspletosaurus the same length as an adult Albertosaurus is heavier and more powerfully built. This gives it the appearance of Tyrannosaurus, but this resemblance is superficial. Numerous differences between the two animals, such as the lack of the postorbital extending into the orbit and no contact between the nasal and premaxilla below the external nares, indicate that Daspletosaurus is distinct from Tyrannosaurus (see also Russell, 1970).

As yet, Daspletosaurus is too poorly represented with skulls and skeletons to determine the full range of variation, including individual, sexual and ontogenetic. The largest individual (CM 9401)is represented by a nearly complete right lacrymal larger than that of the holotype of T. rex (CM 9380). This is suggests a skull with a premaxillary-occipital condyle length of over 1200 mm. A detailed osteology of Daspletosaurus is in preparation.