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Senter, P., & J. H. Robins. 2005. Range of motion in the forelimb of the
theropod dinosaur Acrocanthosaurus atokensis, and implications for predatory
behaviour. Journal of Zoology 266(3): 307-318.
"Casts of forelimb elements of the Cretaceous theropod dinosaur
Acrocanthosaurus atokensis were manually manipulated to determine range of
motion and infer function. It was found that the humerus can swing
posteriorly into a horizontal position but can neither swing laterally to
glenoid height nor anteriorly much beyond the glenoid. The forearm can
approach but not achieve full extension and right-angle flexion. Pronation
and supination are precluded by immobility of the radius relative to the
ulna. Motion also seems to be restricted at the wrist. The palm faces
medially, and digital movement is subtransverse. All three digits are
capable of extreme hyper-extension. Digits I and II converge during flexion.
Only digit III can be abducted or adducted. The limited anterior range of
brachial motion infers that Acrocanthosaurus first apprehended prey orally,
using the forelimb afterwards to secure its grip or deliver fatal blows.
Acrocanthosaurus could only manually grasp prey that was beneath its chest,
towards which it may have used its mouth to move prey. Struggling prey would
have impaled itself further upon the permanently and strongly flexed first
ungual. The range of motion in the forelimb of Acrocanthosaurus resembles
that of Herrerasaurus and Dilophosaurus, and exceeds that of Tyrannosaurus.
Acrocanthosaurus exhibits a greater manual range of motion than ornithomimid
and deinonychosaurian coelurosaurs, but less at the shoulder and elbow.
Coelurosaurian theropods exhibit reduced digital flexion and
hyper-extension, which suggests a change in the use of the manus in