Article: Structure and function of the pectoral girdle and forelimb of Struthiomimus altus (Theropoda: Ornithomimidae)

The forelimb and pectoral girdle of Struthiomimus altus are described for the first time. The ornithomimid pectoral girdle differs from that of other theropods in having a higher scapular prominence (acromion process), an anterior flange on the supraglenoid buttress, and a narrow, attenuated coracoid.Osteological and myological comparisons with recent reptiles and birds, combined with muscle scar evidence, suggests that the primary girdle of Struthiomimus was oriented somewhat laterally, as in recent crocodiles and lizards, and that it was mobile with respect to the body wall. The potential for extensive protraction and retraction of the humerus is evident, endowing Struthiomimus with extensive forereach abilities, combined with limited rotational potential.In the manus the offset first digit differs from the usual theropod condition in being rotated outwards, away from the midline of the hand. Digits II and III are incipiently coalesced and functioned as a unit. The osteological evidence suggests that the manus of Struthiomimus operated as a hooking and clamping structure, rather than as a grasping or raking one.