Meeting Abstract

43.6  Wednesday, Jan. 5  Phylogenetics, evolution, and development of ruminant cranial appendages: insights into hypotheses of homology BRAKORA, K.A.*; DAVIS, E.B.; LEE, A.H.; Department of Integrative Biology, University of California, Berkeley; Museum of Natural and Cultural History, and Department of Geology, University of Oregon; Department of Anatomy, Midwestern University kbrakora@berkeley.edu

Recent revisions of ruminant phylogeny have important but overlooked implications for our understanding of ruminant morphological evolution, particularly for cranial appendages (i.e. headgear). Previously, the arrangement of clades lacking headgear within ruminants had supported hypotheses of independent origins for each type of headgear. However, current topologies have resurrected the possibility that cervid antlers, bovid horns, giraffid ossicones, and the pronghorns of Antilocapra share deep developmental homologies despite major differences in adult gross morphology. We review the existing information about the histogenesis of each type of headgear, including an extinct group of ruminants (paleomerycids). We evaluate traditional hypotheses of homology in light of current phylogenies and existing developmental data. The most important gaps in knowledge surround ossicones, pronghorns, and the earliest stages of development of each type of headgear. Finally, we show that further study of paleomerycids will likely play a key role in understanding the evolution of giraffid and antilocaprid headgear.