The Dimerelloids comprise the largest rhynchonellid brachiopods and were restricted to hydrocarbon seeps and hydrothermal vents where they dominated the macrofauna for 230 million years, crossing both the Permian-Triassic and Triassic-Jurassic mass extinctions.  After the Early Cretaceous, chemosymbiotic mollusks took over the ecosystem and rule today.  There are still many questions about why brachiopods were so successful in this ecosystem.  What was their physiological advantage?  How did they survive multiple mass extinctions? Were they chemosymbiotic or simply successful filter feeders? Why did they finally disappear?  A potential key location for understanding the genesis of this dynasty lies in the massive barite deposits of the Upper Devonian Slaven Chert of northcentral Nevada.  Unfortunately, diagenetic and low-grade metamorphic alteration has obliterated the classic hydrocarbon seep petrofabrics and left the Dzieduszyckia brachiopods poorly preserved as molds. This talk will explore the challenges in assessing paleoecological, petrographic, and geochemical data from highly altered deposits.  Furthermore, by focusing on brachiopods—a phylum with no modern symbionts—the talk will also raise difficult questions on how to address complex geobiological systems in the geological record when there are no known measurable criteria.

Dr. Russell Shapiro has studied fossil microbialite structures from the modern Bahamian stromatolites to the Paleoarchean mats of South Africa. After receiving his Ph.D. from the University of California, Santa Barbara, he taught at different institutions around the country before settling at Chico State in 2006.  In addition to his academic career, Dr. Shapiro has been active in paleontological resource assessment for environmental impact reports, conducting fieldwork for federal agencies throughout the western states.

For zoom information, please get in touch with Rey Garduño (rgarduno@stanford.edu)