Biomechanical Reconstruction of the Appendicular Skeleton in Three North American Jurassic Sauropods

• Main Author: Wilhite, Ray
• Other Authors: Judith A. Schiebout
• Format: Others
• Language: en
• Published: LSU 2003
• Subjects: Geology and Geophysics
• Online Access: http://etd.lsu.edu/docs/available/etd-0408103-003549/

Forelimb and hindlimb articulation, reconstructed musculature, and function were examined in Apatosaurus, Diplodocus, and Camarasaurus. A technique was developed using a Microscribe three-dimensional digitizer to capture external morphological data for skeletal reconstruction and determination of taxonomically useful features. The appendicular musculature of Alligator mississippiensis was dissected to determine form, function, origin, and insertion of muscles to aid in reconstruction of sauropod musculature. Contrary to the literature, M. caudofemoralis longus was found to originate primarily from the lateral surfaces of the proximal chevrons instead of the bodies and transverse processes of the caudals, demonstrating that chevron morphology is indicative of the size, shape, and extent of M. caudofemoralis longus in fossil archosaurs. Apatosurus and Diplodocus were found to have narrower chests than Camarasaurus with forelimbs situated directly under their bodies. Forelimb posture differences between taxa were indicated by the position of the humeral head, morphology of the distal humeral condyles, and the orientation of the posterior process of the ulna. The scapulae in all three taxa were oriented subhorizontally. Hindlimb articulation was found to be related to the shape of the femur and pelvis width. The medial condyles of the femur were longer than the lateral condyles in diplodocids, producing a narrow stance, while the femoral condyles of Camarasaurus were coequal in length, producing a relatively wide stance. This stance would have resulted in wider Camarasaurus trackways than those of diplodocids. Limb motion was restricted to a single plane. Rotation of the brachial and antebrachial joint was constrained by osteology with the brachial joint limited to between 33º and 40º of rotation, and the antebrachial joint limited to no more than 55º of rotation. Femoral joint rotation was limited to between 30º and 37º based on changes in the length of M. caudofemoralis longus, and rotation of the femerotibial joint was restricted by osteology to between 47º and 55º. M. caudofemoralis longus was relatively larger in Diplodocus than in either Camarasaurus or Apatosaurus based on chevron morphology. These results indicate that tripodal rearing, as sometimes proposed for diplodocids, was not common, based on stance and M. caudofemoralis longus contraction length.