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Jocelyn Sessa, assistant professor, Department of Biodiversity, Earth and Evironmental Science, Drexel University

Jocelyn Sessa, PhD

Assistant Professor, Department of Biodiversity, Earth & Environmental Science
Assistant Curator, ANS
Department of Biodiversity, Earth and Environmental Science
Office: ANS, Room 304
Phone: 215.299.1149


  • BA, Geological Sciences, State University of New York at Geneseo, 2000
  • MS, Geology, University of Cincinnati
  • PhD, Geosciences, Penn State, 2009

Research Interests:

  • Paleoecology
  • Ocean Acidification
  • Extinction Recovery Dynamics
  • Global Warming


Jocelyn Sessa, PhD, is a paleobiologist who uses the fossil record as a natural laboratory to study times of change in earth’s history. Her research melds fossil and modern data to elucidate the response of mollusk faunas (clams and snails) to environmental perturbations across space and time. Sessa’s studies span a wide range of events, from the mass extinction that killed off the dinosaurs to past climatic fluctuations, including intervals of past and present global warming. By analyzing the chemistry of mollusk shells, she also reconstructs the climatic conditions that affected ecosystems.

A new research initiative is focused on determining historical baselines for modern ocean acidification, to ascertain whether certain regions or species in the global ocean may be more resilient to future changes in ocean chemistry than others. Sessa’s hunt for mollusks is a worldwide endeavor, with fieldwork along the US eastern seaboard, the US Gulf Coast, California, Romania and Angola. An important facet of her scholarship is mentoring high school through graduate students in research projects. Sessa is passionate about making science accessible to everyone. Since 2007, she has participated in programs to engage groups under-represented in the sciences, and is excited to continue this work in the Philadelphia Area.

Selected Publications:

  • Jardine, P.E., Harrington, G.J., Sessa, J.A., Dašková, J. 2018. Drivers and constraints on floral latitudinal diversification gradients. Journal of Biogeography 45:1408-1419; doi:10.1111/jbi.13216.
  • Self-Trail, J.M., Robinson, M.M., Bralower, T.J., Sessa, J.A., Hajek, E.A., Kump, L.R., Trampush, S.M., Willard, D.A., Edwards, L.E., Powars, D.A., and Wandless, G.A. 2017. Coastal marine response to global climate change during the Paleocene Eocene Thermal Maximum, Salisbury Embayment. Paleoceanography 32:1-19 doi:10.1002/2017PA003096.
  • Janssen, A.W., Sessa, J.A., and Thomas, E. 2016. Pteropoda (Mollusca, Gastropoda, Thecosomata)from the Paleocene-Eocene Thermal Maximum of the United States Atlantic Coastal Plain.Palaeontologia Electronica. 19.3.47A: 1-26.
  • Knoll, K., Landman, N. H., Cochran, J. K., MacLeod, K. G., and Sessa, J. A. 2016. Microstructural preservation and the effects of diagenesis on the carbon and oxygen isotope composition of Late Cretaceous aragonitic mollusks from the Gulf Coastal Plain and the Western Interior Seaway. American Journal of Science 316:591–613.
  • Sessa, J.A., Larina, E., Knoll, K., Garb, M. Cochran, J.K., Huber, B.T., MacLeod, K.G., Landman, N.H. 2015. Ammonite habitat revealed via isotopic composition and comparisons with co-occurring benthic and planktonic organisms. Proceedings of the National Academy of Sciences 112:15562-15567.
  • Sluijs, A., van Roij, L., Harrington, G.J., Schouten, S., Sessa, J.A., Levay, L.J., Reichart, G.J., Slomp, C.P. 2014. Warming, euxinia and sea level rise during the Paleocene-Eocene Thermal Maximum on the Gulf Coastal Plain: implications for ocean oxygenation and nutrient cycling. Climate of the Past 10:1421-1439.
  • Sessa, J.A., Callapez, P.M., Dinis, P.A., Hendy, A.J.W. 2013. Paleoenvironmental and paleobiogeographical implications of a Middle Pleistocene mollusc assemblage from the marine terraces of Baía das Pipas, Angola. Journal of Paleontology 87:1016-1040.
  • Sessa, J.A., Ivany, L.C., Schlossnagle, T.H., Samson, S.D., Schellenberg, S.A. 2012. The fidelity of oxygen and strontium isotope values from shallow shelf settings: Implications for temperature and age reconstructions. Palaeogeography, Palaeoclimatology, Palaeoecology 342-343:27-39.
  • Sessa, J.A., Bralower, T.J., Patzkowsky, M.E., Handley, J.C. Ivany, L.C. 2012. Environmental and biological controls on the diversity and ecology of Late Cretaceous through early Paleogene marine ecosystems in the U.S. Gulf Coastal Plain. Paleobiology 38: 218-239.
  • Sessa, J.A., Patzkowsky, M.E., Bralower, T.J. 2009. Impact of lithification on the diversity, size distribution, and recovery dynamics of marine invertebrate assemblages. Geology 337:115-118.
  • Alroy et al. 2008. Phanerozoic trends in the global diversity of marine invertebrates, Science 321: 97–100.
  • Gibbs, S.J., Bown, P.R., Sessa, J.A., Bralower, T.J., Wilson, P.A. 2006. Nannoplankton origination and extinction across the PETM, Science 314:1770-1773.