Meeting Abstract

45.2  Saturday, Jan. 5  Fish fingers and the origin of limbs: A compendium of recent progress DAVIS, M.C.; Kennesaw State University mdavi144@kennesaw.edu

Recent comparative developmental studies and paleontological discoveries have provided us with exciting new insights into how the unique attributes of the tetrapod limb, namely digits, may have evolved. Developmental studies in the basal actinopterygian Polyodon and in the chondrichthyans Raja, Chiloscyllium, and Scyliorhinus reveal that key appendage patterning genes are far more conservative in their expression and function than first estimated from studies based on derived osteichthyan taxa alone. Likewise, new fossil evidence from several sarcopterygian taxa also reveals a more conservative pattern of paired fin skeletal evolution than previously thought. Together, these discoveries constitute growing evidence that tetrapod digits are an elaboration or expansion of a previously existing developmental program. This suggests that the origin of digits would have entailed regulatory changes to ancient and conserved gene networks, but not the addition of new key genes or gene pathways.