An investigation of Peramorphosis in isorophinid edrioasteroid echinoderms

University Of Tennessee Knoxville, Knoxville TN

Investigators

Abstract

Investigating the Role of Heterochrony in the Evolution of Edrioasteroids Colin Sumrall, University of Tennessee, Knoxville EAR-0745918 Heterochrony, evolution by changing the timing of morphological change during ontogeny, is an important evolutionary mechanism throughout the Phanerozoic. In most clades, paedomorphosis (adult descendents having characteristics of the ancestral juvenile) is commonly cited as the dominant pattern. In isorophids, however, peramorphosis (adult descendants with characteristics that are overdeveloped with respect to their ancestors) is the dominant pattern in the ambulacral feeding apparatus. This two-year project aims to collect and interpret phylogenetic, and ontogenetic, data for isorophid edrioasteroids and use these data to investigate the different ways in which isorophid edrioasteroids are specializing via heterochrony. Phylogeny will be reconstructed using maximum parsimony on a genus level data matrix for all isorophid edrioasteroids. Ontogeny will be studied using elemental fate mapping and allometric studies of growth. These two areas will be combined to investigate portions of the phylogenetic history of isorophids where heterochrony played an important role and determine if different styles of heterochrony are dominant during the recovery from two mass extinctions (end Ordovician and Frasnian/Famennian). This project will involve graduate and undergraduate students directly into interdisciplinary research where they will learn new techniques. Minority undergraduate students will be included by collaboration with the NSF-funded East Tennessee Geosciences Program. Results will be incorporated into a web-based activity on organic evolution via heterochrony and middle school education modules on evolution for use in east Tennessee classrooms.