ANATOMY AND FUNCTION OF DIGIT III OF THE TYRANNOSAURUS REX MANUS

In northeastern Montana's Hell Creek formation, a Tyrannosaurus rex has been unearthed with three fingers on each hand. The existence of digit III had previously surmised because of a joint surface on the ulnar aspect of the base of metacarpal II. The phalanges of digit III and its metacarpal are fused into one slightly flexed unit, with proximal and radial joint surfaces. Sturdy dorsoulnar and volar muscle attachments are present on the base of the metacarpal. The anatomical findings suggest that the wrist of Tyrannosaurus rex had considerable power and that its hands could have been quite useful in stabilizing its prey or carrion.