Meeting Abstract

57.4  Tuesday, Jan. 6  A dynamic approach to digital homology in Tetanura (Dinosauria: Theropoda) CHOINIERE, Jonah N*; CLARK, James M; XING, Xu; FORSTER, Catherine A; George Washington University, Washington, DC; George Washington University, Washington, DC; Institute for Vertebrate Paleontology and Paleoanthropology, Beijing, China; George Washington University, Washington, DC jonahc@gwu.edu

A long-standing issue in evolutionary biology is the conflict between the identities of the three manual digits in tetanurans, the theropod clade whose crown lineage is Aves and whose stem members include large terrestrial predators such as Allosaurus. In Aves, embryological data strongly suggest that the manual digits correspond with digits II, III and IV of the primitive tetrapod bauplan. However, paleontological data identifies the three manual digits of non-avian tetanurans as I, II and III. This apparently non-homologous relationship has been frequently cited to falsify the theropod origin of birds. The tetanuran manual digit homology problem is analagous to biochemical sequence alignment because uncertainty of the positional identity of tetanuran manual elements implies multiple possible sets of statements of primary homology of manual digits across the clade. A dynamic homology approach is an appropriate means of selecting an optimal hypothesis of primary homology via maximum congruence. We therefore employ a dynamic homology approach to resolve the identity of tetanuran digits, incorporating information from the unique manual morphology of a new Chinese theropod closely related to tetanurans. This approach is the first of its kind for the Dinosauria. Assuming that the digits of birds have been positionally identified without error, our data indicate that for tetanurans the digits of the hand optimally align with II, III, and IV of the avian manus. Our results are compatible with a range of developmental models that have been proposed to resolve the digital homology conflict.