The largest terrestrial carnivores of all time, the carnosaurs, formed a group of theropods that, although not closely related (Sect. 11.1), show considerable resemblance to one another, probably as a result of convergence. The families Megalosauridae and Allosauridae were, however, more nearly related to one another than to the Tyrannosauridae. They had neck vertebrae with a ball and socket joint at the front and a socket on the back, whereas the neck vertebrae of the Tyrannosauridae were almost flat at both ends. All the carnosaurs had well developed olfactory and optic lobes of their brains. One or two genera may well even have possessed stereoscopic vision (Sect. 9.3.1; Molnar and Farlow 1990). Traditionally, carnosaurs have been illustrated walking with the vertebral column inclined at an angle of at least 45 ° to the horizontal, as in the drawing of Tyrannosaurus rex (Fig. 122). This, however, is no longer universally accepted

■ Fig. 122. Tyrannosaurus (Tyrannosauridae; Upper Cretaceous; length ca. 12 m). (Cloudsley-Thompson 1994)

as being correct. The idea was originally based on the work of E.D. Cope in 1886, supplemented by analogy with kangaroos. The centre of mass of the body must lie in the immediate area of the hips. To be balanced, the trunk would either have been held more steeply or its weight was counterbalanced by the tail raised from the ground (Alexander 1985). It is shown in the latter position in most of the illustrations of carnosaurs on the following pages.

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