The evolution of synapsids is documented by an unusually rich fossil record, extending over 300 million years. Primitive synapsids, the pelycosaurs, are the most conspicuous terrestrial vertebrates of their time, and their fossil remains record the earliest successful adaptive radiation of amniotes to a broad array of herbivorous and predators modes of life. The PIs will undertake a thorough reassessment of the phylogenetic relationships of pelycosaurs by combining detailed anatomical studies of specimens with a cladistic analysis that considers a large suite of characters. Their first hand knowledge of this group, previous studies of numerous pelycosaur taxa, and availability of representative specimens of three outgroups for direct osteological comparisons will eliminate the need to rely heavily on outdated literature. In addition to providing an assessment of the ingroup relationships of pelycosaurs, the present study will assess the relationship of pelycosaurs to other Paleozoic vertebrates, including their therapsid descendants. Computer algorithms that utilize cladistic techniques will be used to analyze phylogenetic relationships. This project will provide a solid basis for the analysis of the paleoecology and paleobiogeography of pelycosaurs. The PIs also expect to be able to construct a macroevolutionary model of the group and to address the perplexing problem of the origin of amniotes (higher vertebrates that include recent reptiles, birds, and mammals).
