Research Training Program

Smithsonian Institution
National Museum of Natural History

PROJECT SUMMARY
1997

Carla S. Nappi
Harvard University
Cambridge, Massachusetts
Douglas H. Erwin, Ph.D.
Supervising Scientist
Department of Paleobiology
"The project has been incredible in so many ways; I've learned to think in completely different ways than I was previously accustomed to. My advisor has been wonderfully helpful, insightful, and has inspired me to pursue a career in paleobiology."

A phylogenetic analysis of Permian and Triassic subulitid gastropods:
implications for survival of the end-Permian mass extinction

ABSTRACT
About 250 million years ago, life on Earth suffered a considerable blow in the end-Permian mass extinction. Some 90 percent of all marine species were decimated in the greatest known disaster in the history of life on the planet. However, some species did manage to make it across the Permo-Triassic boundary, effectively surviving the mass extinction. These species, called "Lazarus Taxa", can offer valuable clues regarding the nature and duration of the end-Permian extinction. This study involved investigation of the Subulitacea, an extinct superfamily of gastropods that contains some species which crossed the Permo-Triassic boundary. Available collections of subulitid gastropods were examined and characters with apparent evolutionary significance were noted and used to create a phylogeny, or proposed evolutionary history, of the superfamily. Then, the age and geographic distribution of each species was determined by compiling biogeographic and stratigraphic data from collected and described specimens. Based on an analysis of the inferred evolutionary history (phylogeny) and the biogeographic and stratigraphic data, we attempted to determine whether the "Lazarus" subulitids shared common morphological or biogeographic characters which contributed to their survival of the end-Permian extinction. The research revealed that, while there were no obvious shared morphological characters among the Lazarus taxa, it seems that surviving species occupied similar biogeographic areas. This has important implications for understanding the ways that major extinction events shape evolutionary processes.

This research was supported by a grant from the National Science Foundation Research Experiences for Undergraduates program, Award Number DBI-9531331.

Letter of Gratitude