Event

The Department of Earth & Environmental Science

University of Pennsylvania

Invites you to attend a EES Seminar Series

Friday, January 13th - 3:00 PM

"New tristichopterids (Sarcopterygii, Tetrapodomorpha) from the Late Devonian Catskill Formation of Pennsylvania, U.S.A.: implications for the phylogeny of the group"

Tristichopteridae is an extinct cosmopolitan clade of large-bodied, predatory, lobe-finned vertebrates (Sarcopterygii) from the Devonian Period (419–359 Ma). It has the phylogenetic distinction of being the sister group to Elpistostegalia, that clade within which the vertebrate fin-to-limb transition occurred. Recent efforts to survey tristichopterid diversity in the Upper Devonian Catskill Formation of Pennsylvania include descriptions of three new species and re-descriptions of two historical species. These works support phylogenetic and historical biogeography analyses that offer new hypotheses about the origin of the group and its history of diversification and distribution. Results suggest that Catskill Formation tristichopterids belong to a highly-nested clade of mostly Famennian forms that had a Euramerican origin before expanding into Gondwana. Detailed study of tristichopterids additionally offers an opportunity to understand how the selective pressures of Late Devonian freshwater systems influenced the pattern of evolution in large-bodied aquatic sarcopterygians. Such work has relevance to the vertebrate fin-to-limb transition and the clade’s shift to shallow water, and eventually subaerial, environments.

Dr. Jason Downs

Vertebrate Paleontology

Academy of Natural Sciences of Drexel University

Dr. Jason Downs is an Associate Professor of Biology at Delaware Valley University, Research Associate in Vertebrate Paleontology at the Academy of Natural Sciences of Drexel University, and is on the faculty at the Wagner Free Institute of Science. He earned B.A. degrees in Biology and Geology (now Earth and Environmental Science) from the University of Pennsylvania and a Ph.D. in Geology and Geophysics from Yale University. Downs has done field research on Devonian (419–359 Ma) rock formations throughout the world and was part of the team that discovered and described Tiktaalik roseae, a fossil species that sheds important light on the vertebrate fin-to-limb transition. He has actively researched and published on Pennsylvania fossils for his entire professional career.