Meeting Abstract

16.2  Tuesday, Jan. 4  New data on the morphological changes in the pectoral fin rays during the fin to limb transition TAFT, Natalia K*; SHUBIN, Neil; LAUDER, George; University of Chicago; University of Chicago; Museum of Comparative Zoology, Harvard University nktaft@uchicago.edu

Changes to and reduction of the dermal fin rays are crucial steps in the evolutionary transformation from fins to limbs. However, until recently morphological changes in the dermal fin rays have been largely overlooked in analyses of the origin of limbed vertebrates. We address this gap in our understanding this transition by comparing the morphology of the pectoral fin rays in three key fossil taxa, the rhizondontid Sauripterus, tristochopterid Eusthenopteron and elpistostegid Tiktaalik and the extant Austalian lungfish Neoceratodus. We present new data from CT scans of the pectoral fins of Tiktaalik and Neoceratodus. Previously, extensive overlap of the fin rays (dermal skeleton) and the radials (endochondral skeleton) was known only in the fossil sarcopterygian taxa. Our new data shows extensive overlap of the fin rays and radials in the living Neoceratodus. We also discuss changes in the symmetry of the arrangement and robusticity of the pectoral fin rays among the fossil taxa and their functional implications.