Invertebrate Paleontology Staff & Associates


Jocelyn A. Sessa, PhD

Assistant Curator of Invertebrate Paleontology
Assistant Professor, Department of Biodiversity, Earth & Environmental Science


Jocelyn Sessa 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.

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 she is excited to continue this work in the Philadelphia Area.

For more details about Jocelyn’s work, please check out:

 scientist in white shirt in front of starfish specimen

Dr. Alejandra Martinez-Melo

Collection Manager of Invertebrate Paleontology

Alejandra is responsible for the care, maintenance, and management of the Invertebrate Paleontology collection. She obtained her Biology degree, her Masters and PhD in Marine Sciences and Limnology, from the National Autonomous University of Mexico (UNAM). After obtaining her Ph.D., Alejandra was a postdoctoral fellow at the Institute of Geology (UNAM), and at the Center of Paleontology Research (CR2P), Sorbonne University, France. Alejandra conducts research on the taxonomy, systematics, and biogeography for Post-Paleozoic Echinoids; for more details about her research, go to


Rosie Oakes, PhD

Research Associate in Invertebrate Paleontology


Rosie is an earth, ocean, and climate scientist interested in the impact of global climate change on natural and human systems. Her PhD and post-doctoral research were focused on understanding how ocean acidification, caused by increased carbon dioxide from the atmosphere dissolving in the ocean, impacted marine plankton. Rosie studied a group of tiny swimming snails called pteropods, hailed as the canary in the coal mine for ocean acidification. During her PhD, Rosie designed a method to measure the thickness of the shells of these tiny plankton to assess their risk from ocean acidification. Rosie continued to study these sentinel organisms during her three-year postdoctoral research fellowship in the Invertebrate Palaeontology department at the Academy. Rosie, along with other members of the Invertebrate Paleontology group, is leading a research project investigating how pteropods off the coast of Shetland, Scotland have been impacted by changing ocean conditions over the past 200 years.

Rosie is a Research Associate at the Academy but spends most of her time working as an International Climate Services Scientist at the UK Met Office, translating outputs from global climate models into a format that is accessible to stakeholders and decision makers around the world. Rosie’s current projects involve understanding food security in China and evaluating cross-border climate risks in Europe.

For more details about Rosie’s work, check out her website:


Alexandra Buczek

Doctoral Candidate in Comparative Biology, Richard Gilder Graduate School at the American Museum of Natural History

Advised by Melanie J. Hopkins and Jocelyn A. Sessa

Alexandra is a geologist and paleobiologist primarily interested in the influence of climate change on nearshore marine ecosystems. Alexandra’s PhD research focuses the response of Southern Californian coastal marine mollusk communities to climate change during the Plio-Pleistocene period (5.3 – 1.5 million years ago), during which the Earth experienced major warming followed by a drastic cooling into the Pleistocene glacial periods. Her multidisciplinary research brings together isotope stratigraphy, paleoecological statistical analyses, and stable isotopic data in order to determine the main changes in mollusk communities during a period of major climate change as well as deduce the environmental drivers behind those observed changes. 

For more details about her work, please don't hesitate to contact Alexandra through email.

 bryce at grand canyon

Bryce Koester

Graduate Student, Department of Biodiversity, Earth & Environmental Science

Bryce is a first year graduate student at Drexel University with a background in paleontology. Her research interests are centered around marine invertebrates, such as mollusks and foraminifera, and their responses to anthropogenic stressors. During her time as an undergraduate, Bryce researched the effects of heavy metal pollution on the mutation frequencies of foraminifera. At the Academy, Bryce will investigate the direct and indirect impacts of ocean acidification on modern pteropods, a critical organism in marine communities. Bryce is passionate about increasing the accessibility of environmental science to policy decision makers and the public and is looking forward to participating in outreach through the Academy of Natural Sciences of Drexel University.

 scientist at microscope

Andrew J. Fraass, PhD

Research Associate in Invertebrate Paleontology

As a micropalaeontologist and palaeoceanographer, Andy Fraass works to understand how past examples of climate change and evolution interact. He does this using a tiny group of single celled marine zooplankton called planktic foraminifera.

Fraass is currently working to understanding the role of biology in the carbonate cycle. The oceans currently absorb an outsized amount of carbon dioxide. Planktic foraminifera produce carbonate (CaCO3) shells. Those shells make up a substantial amount of the carbonate on the seafloor. This carbonate acts like a buffer, helping to stabilize the ocean’s chemistry. Those shells are also the world’s best fossil record, one good enough we can examine how species evolve, not genera or families like we usually need to use. We know that when these plankton go extinct there’s a change in the amount of carbonate deposited. Using a new database with >50 years of scientific ocean drilling data, Andy works to understand what the key risks are to plankton during several past examples of climate change and how those key risks are expressed in the deposition of carbonate.

Fraass is a Research Associate with the Academy, but he can normally be found at the University of Bristol where he is a Vice Chancellor’s Fellow in Earth Sciences.

For more more details about Andy’s work, please check out:

 man with grey shirt and messenger bag with black strap

Daouda Njie

Curatorial Assistant

Daouda is a recent Drexel graduate. With a degree in Environmental Science and a focus on evolution and ecology. He works in the collection managing, georeferencing, and digitizing specimens. His interest is in curating and maintaining large online databases for museum collections. In his free time, he enjoys rock climbing, hiking, and photography.

 woman with white shirt and hat with bug on arm in field

Alexis Srogota

Undergraduate Research Assistant


Alexis is a senior Biology major with a concentration in Ecology, Evolution, and Genomics. Her passions lie in wildlife conservation and climate change research. Through her time in this department, she has worked to curate and care for the collection as well as image many of the specimens. She has also worked alongside Dr. Sessa and Dr. Hendy on the EPICC research project and is now continuing to work on using pteropods as indicators of ocean acidification. In her free time, Alexis likes spending time outside, collecting shells, photography, and looking at bugs.