Wednesday, Nov. 8, the College of William and Mary’s Geology Department hosted Assistant Curator of Paleontology at the Virginia Museum of Natural History Dr. Adam Pritchard to give a presentation on the evolution of reptiles. In his presentation, Pritchard discussed the rise of reptiles, beginning in the age of dinosaurs, through specimen-based research and three-dimensional scanning technology.
Pritchard earned his B.A. in biology from McDaniel College and his Ph.D. in anatomical sciences from Stony Brook University. After obtaining his Ph.D., Pritchard went on to conduct fieldwork around the United States and research with Smithsonian Museums before working at the Virginia Museum of Natural History.
Pritchard began the presentation with an overview of the Mesozoic Era and a display of diagrams of modern reptile lineages.
“We see very rapidly beginning in the Triassic emergence of a vast array of different reptile lineages, body plans and feeding eco-morphologies,” Pritchard said. “Just a huge diversity of different taxa. And in a way, that diversity is so vast and to emerge so rapidly that it’s somewhat overwhelmed, we have a nasty impact on understanding when those divergences really occur.”
The age of reptiles started with dinosaurs 252-66 millions years ago, and has since branched out into a largely diverse body of reptile species. This diversification of reptiles started with the Permo-Triassic extinction, which was a tectonic shift that caused a rift in many species. According to Pritchard, many bizarre and disparate species emerged in the Triassic period.
Pritchard posed two questions to the audience, asking “How are they related to one another?” and “What does this tell us about the nature of the Permo-Triassic diversification?” To approach these questions, Pritchard introduced an overview of methods used to analyze fieldwork, then offered reflections.
“I use a number of different sort of project methodologies to attack those kinds of questions,” Pritchard said. “All of my research is very much specimen-based, and I do engage in fieldwork and museum based collections work to identifying specimens that are really relevant to understanding this sort of diversity of basic description and analysis and phylogeny context.”
Pritchard mentioned his fieldwork discovering specimens in Virginia and Arizona, but noted that his favorite task is 3D modeling because it helps him see small, almost microscopic bones in the fossils he studies.
“For a lot of those specimens accessing the data is really difficult; the body size is small and inaccessible for physical preparation,” Pritchard said. “So I actually use CT scanning and three dimensional modeling of sort of delicate fossil specimens for description and analysis. And then finally all of that comes together in a sort of phylogenetic analysis, building evolutionary trees based on those anatomical relationships to define the aspects of the early reptile radiation.”
“Phylogeny has always produced ghost lineages like, there’s never superfect congruity in the splitting of different taxa,” Pritchard said. “But when you’re doing phylogeny around a major tumultuous event in Earth’s history, then it becomes weird.”
When analyzing evolutionary trees of reptiles, Pritchard noted that anatomical disparities were frequent. He referred to ghost lineages, known as the missing spaces in evolutionary trees that should be present. The species lines show increasing disparity between animals as time goes on, thus diversifying the world of reptiles.
“Phylogeny has always produced ghost lineages like, there’s never superfect congruity in the splitting of different taxa,” Pritchard said. “But when you’re doing phylogeny around a major tumultuous event in Earth’s history, then it becomes weird.”
Pritchard emphasizes that from the 1980s all the way to the present, researchers are still discovering skeletons of these animals. Some of these fossils have unprecedented anatomy, and the types found are primarily microvertebrate fossils, meaning they are very small. Rather than looking at the examples as disconnected, singular incidents, Pritchard considers them as a part of a more intricate history.
“I no longer look at these things as examples of single, weird examples of diversity and disparity,” Pritchard said. “I see these in a way as the seeds for this incredibly complex garden of diversity of contribution to that phylogenetic narrative that could emerge from any discovery that expands the understanding of lineages during the Permian and the Triassic periods.”
For Pritchard, the process is ongoing and holds potential to lead to new understandings.
“Even the things that we have only just really begun to analyze and interpret could really change our understanding of the world at the beginning of the age of reptiles,” Pritchard said.
Funding for Pritchard’s research comes from the Virginia Museum of Natural History Foundation, The Peter Buck Foundation and the National Science Foundation for Collections-Based Research.
Many attendees stayed for a question and answer session following Pritchard’s presentation.
After the event, Orion Fellows ’24 shared their initial connections to Pritchard and his work.
“I’m here because Adam is a friend of mine because I went on the Wyoming dig with him a few years ago,” Fellows said. “And since then, I have also visited his museum where he’s a curator. And we also worked on a dig in Virginia last year together.”
Professor of geology Rowan Lockwood also attended the talk, sharing praise of Pritchard’s work.
“I teach the Age of Dinosaurs class, and every time I teach that class, I try to have a person who works on dinosaurs or works during the time of dinosaurs to come out and tell us a little bit more about the dinosaurian world,” Lockwood said. “And I thought Adam was an excellent choice because a lot of people are familiar with dinosaurs, but they don’t know all of the really cool and wacky creatures that are living alongside dinosaurs.”
Lockwood also reflected on Pritchard’s impact on the overall study of the Mesozoic period.
“It’s like the dinosaurs get all the attention, and I think Adam has really been a big proponent of studying everything that exists in the Mesozoic,” Lockwood said. “Everything that, you know, is living alongside the dinosaurs. And so, I thought he did a beautiful job of bringing his fieldwork and his museum work to life.”
For students interested in participating in digging a site, Lockwood recommends attending Pritchard’s summer course in Lynchburg, Va.
“I would encourage folks, if you have ever dreamt of digging up dinosaurs, the summer dinosaur dig course that Adam offers in collaboration with the University of Lynchburg is an amazing once-in-a-lifetime opportunity,” Lockwood said.
