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THE UNIVERSITY OF CALGARY Eric Snively A ... - Ohio University

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phylogenetic bracketing Wtmer 1995) as a means of infemng intemetatarsal<br />

ligaments in extinct forms. Inference of soft tissues is still possible with broader<br />

phylogenetic comparison and extrapolatory inference (Bryant and Russell 19921,<br />

as discussed in Chapter 1.<br />

Ligaments connect metatarsals generally in tetrapods, but muscles and<br />

tendons do not normally occur between weight bearing metatarsals. Close<br />

conformity of articular surfaces in theropods argues against the neomorphic<br />

presence of muscles; negligible fiber lengths would prevent the muscles from<br />

performing positive work. In contrast to the rarity of muscles and tendons,<br />

proximal ligaments are common between metatarsals (Kerr et al. 1987;<br />

McGregor 2000). Arnongst reptiles, ligaments with oblique distolateral angulation<br />

are present in the metacarpus and metatarsus of lizards (Landsmeer 1981;<br />

McGregor 2000). The presenœ of oblique deep ligaments in Iizards does not<br />

aIIow bracketing for homologous ligaments within the theropod metatarsus.<br />

However, it does show that ligaments of similar angulation to that hypothesized<br />

for the arctometatarsus are mechanically feasible. Overall it may be concluded<br />

that bony correlates for intermetatarsal articulating elements indicate ligaments,<br />

and not tendons.<br />

The interpretation of osteological correlates as ligament scars circumseribes<br />

hypotheses of arthrological dynamics within the arctometatarsus. Soft tissue<br />

anatomy, wupIed with results for range and direction of movement described<br />

above, suggests the following model for intermetatarsal kinematics.

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