DISSERTATION RESEARCH: An integrative assessment of body size and growth patterns in therocephalian synapsids before and after the end-Permian extinction

University Of Washington, Seattle WA

Investigators

Abstract

This award supports two years of doctoral research to complete an investigation of body size and life history (growth and reproduction) tactics in the therapsid ancestors of mammals before and after the end-Permian extinction (ca. 252 million years ago), a period of intense ecosystem instability in which more than 90% of animal species on Earth became extinct. Based on a large sample of mammal-like therapsid fossils from the Karoo Basin of South Africa, we will integrate hard-tissue histology (bone tissue growth) and phylogenetic comparative methods to assess for the first time whether body size reductions and changes in vascular growth patterns recorded in the bones of therapsids were driven by the end-Permian extinction. In doing so, we address how increased environmental stress and instability may influence life history evolution in major vertebrate groups on a macroevolutionary scale. This study will also shed light on the origins of novel life history strategies, such as rapid, determinate (mammal-like) growth in our own mammalian lineage. The funding will assist in the maintenance of an active histological facility and analytical resources to support student projects and lab-based course materials, offering opportunities for professional development of underprivileged future scientists and providing new teaching resources to our institution. Data will be archived on a freely-accessible online database of histology images and similar electronic data repositories (e.g., Paleobiology Database). Additionally, work with South African institutions will strengthen international collaborations and raise awareness of natural history, evolution, and extinction within a newly industrialized country, and will help inform decisions on protecting extant biodiversity by forecasting long term biotic responses to future ecosystem perturbations.