TYRANNOSAURIDAE, Osborn, 1906

Russell, Dale A., 1970, Tyrannosaurs from the Late Cretaceous of western Canada, Ottawa: National Museum of Natural Sciences, Publications in Palaeontology, No. 1 : 2-3

Family TYRANNOSAURIDAE

Diagnosis

Premaxillary teeth reduced in size relative to those of maxilla, 'U'- shaped in cross-section with carinae bordering opposite edges of flat, posteriorly facing surface. Three antorbital fenestrae within maxilla, anteriormost fenestra small and inconspicuous in lateral aspect. Frontals narrow, parietals represented dorsally as longitudinal crest of bone separating supratemporal fenestrae. Supraoccipital enters dorsal border of foramen magnum, paroccipital processes not depressed laterally. Laterosphenoids meet on midline of skull, separating fenestra for optic nerve from ventroanterior opening of pituitary fossa. Spines of cervical vertebrae most powerfully developed in anterior region of neck, length of cervical centra seldom exceeds 10 per cent of that of femur. Length of dorsal centra less than height of centrum. Length of humerus approximately one-third that of femur, only two functional digits present in manus. The length of the pubic boot in adults greater than half total length of pubis. Shaft of ischium pointed distally, frequently with slight ventral recurvature toward tip. Well-developed alae unite ischial shafts ventromedially. Lateral trochanter of femur large, extends to proximal end of bone. The length of the tibia in adults is about 90 per cent of that of the femur. Shaft of third metatarsal constricted dorsally.

Comments

The family group name ' Tyrannosauridae' was proposed by Osborn (1906: 283) and is based on an unquestionably valid genus of carnivorous dinosaur from the Hell Creek Formation of Montana. The family group name ' Deinodontidae', which has often been used as a synonym of Tyrannosauridae , was proposed by Cope (1866: 279, " Dinodontidae "), with Deinodon ( Leidy 1857: 72; 1860: 143) as its type genus. The lectotype of Deinodon horridus {see Cope 1866: 279; Hay 1908: 359) consists of two fragmentary premaxillary teeth of a large theropod from the Judith River Formation of Montana. No topotypic specimens have ever been described from this formation. It has been suggested ( Hay 1908: 353; Matthew and Brown 1922: 374, 383) that Deinodon is congeneric with Gorgosaurus {= Albertosaurus ) from the Oldman and Edmonton formations of southern Alberta. Gilmore (1946: 17) stressed the point that this identity could not be demonstrated in view of the incompleteness of the type teeth of Deinodon horridus and was inclined to doubt that the genus could ever be satisfactorily defined.