Meeting Abstract

13.3  Jan. 4  INTEGRATING PALEOBIOLOGY AND DEVELOPMENTAL GENETICS: CONTRIBUTIONS OF THE FOSSIL RECORD TO THE STUDY OF FIN LOSS IN TELEOST FISH SANTINI, Francesco*; CARNEVALE, Giorgio; University of Toronto; University of Pisa francesco.santini@utoronto.ca

With over 28000 species, teleost fish represent the largest vertebrate clade. Most teleosts rely on the movement of a combination of paired and median fins for their locomotion. As such, fins might be thought to be highly conserved structures. A survey of the morphological diversity of extant and fossil teleosts, however, reveals that some kinds of fins can be very easily modified or lost, while others are much more highly conserved. The pelvic fins, for example, have been lost at least 70 times independently, while the caudal fin is very rarely lost. Until now, relatively little attention has been paid to how fins are reduced or lost. In our presentation we will discuss briefly the pattern of fin loss in teleosts. We will discuss evidence that morphological modules can be identified within the skeletal system of these fishes. We will also show how some of these modules can be modified � likely through processes taking place during the early stages of development � until their final disappearance in adult individuals. Finally, we will formulate some hypotheses about the relationships between morphological complexity and developmental regulatory genes in this clade. These hypotheses could perhaps be tested experimentally using developmental genetic methods. We will also show how fossils play a key role in the study of fin loss in many groups, by providing intermediate stages that illustrate how morphological transitions occurred in lineages now characterized by extant taxa with highly divergent morphologies.