Friday, March 20, Sterling Nesbitt, a paleontologist and professor of geobiology at Virginia Polytechnic Institute and State University, delivered a talk at the College of William and Mary about the Triassic Period and evolution of the archosaur group, the assortment of vertebrates including crocodiles and dinosaurs, in McGlothlin-Street Hall.
Students who attended were eager to learn about paleobiology. One such student, Evelyn Kresse ’26, spoke about her reasons for attending.
“I think dinosaurs are really interesting, and dinosaur science is really cool,” she said. “I really love hearing about research that is new and exciting and learning about new things, especially in the fields of sciences, so I am really excited to hear this talk.”
As the lecture began, Nesbitt described his interest in the emergence of dinosaurs. He outlined how the Triassic differed from today. This era was sandwiched between two mass extinctions and marked by a wide array of reptile groups.
The dominant lifeforms of the Triassic were most closely related to modern crocodiles, Nesbitt explained. He went on to describe how the animals currently associated with the term dinosaur emerged as small creatures 20 million years after many of these other reptile groups.
Nesbitt also discussed the challenges of understanding these animals’ roles in history. Most of the early fossil finds of Triassic dinosaurs were fragmentary, and for many years, few dinosaur relatives were known. However, recent finds have changed this.
Nesbitt explained his research by discussing digs at Ghost Ranch in Abiquiú, N.M., which revealed beds of dinosaur bones. These findings demonstrated that dinosaurs shared the world with their more primitive cousins longer than previously thought. He then discussed another expedition to Tanzania, where he and a team of paleontologists dug for mammal and reptile skulls before finding something more fascinating: the limbs and tail of a creature called Asilisaurus, which is either a close relative of dinosaurs or the earliest dinosaur yet discovered.
“I began thinking, if we can find these animals here, we can find dinosaur relatives here. And the next day we found one,” Nesbitt said.
Finds like this, according to Nesbitt, have dramatically expanded scientific knowledge and have led to the creation of new animal groups, such as the Lagerpetidae, flightless relatives of the winged pterosaurs, and Silesaurids, creatures that share many similarities with primitive dinosaurs.
Nesbitt also said most early dinosaurs were generally small creatures with little to distinguish them from their close relatives. However, this may have helped them survive. The end Triassic mass extinction eliminated the larger and more specialized animals surrounding them.
The classification of Nesbitt’s discovery remains up for debate. Nesbitt discussed how, although some studies have classified Asilisaurus as part of Silesauridae, others have considered it primitive. If so, dinosaurs’ origins would be dated to the mid-Triassic, and many of the traits assumed to be the products of common ancestry between different dinosaur groups would instead be byproducts of convergent evolution.
More research will be needed to refine the evolutionary tree of Archosaurs, the group of reptiles containing crocodiles and dinosaurs, he said.
Nesbitt’s findings have unveiled much about the history of life on Earth. Dinosaurs and their relatives were simply one part of a broader explosion of reptilian life during this period, and they copied the forms of many of their relatives while also diversifying until the mass extinction.
The talk was well-received by students like Alex Chouinard ’27.
“When you think of academia and getting into it as a job, it can feel very abstract and strange, but seeing the professors progress from, ‘We just had these bones and went to New Mexico and then to Tanzania’ was very interesting,” Chouinard said. “I think it can be inspiring to see academia in action.”
Professor of geology Rowan Lockwood also shared her thoughts.
“I thought it was a fabulous talk,” she said. “I really enjoyed the fact that he focused on how fieldwork and how the process of science allows us to answer some of these big fundamental questions in paleobiology. He showed how our understanding of these really crazy organisms changes over time and how it’s influenced by new discoveries and new technologies that we can use to study them.”
Nesbitt hopes students left the talk with a greater understanding of the complexity around the origins of dinosaurs.
“The origin of dinosaurs is way more complex than we ever expected it now, largely because we didn’t know about their close relatives,” he said. “Now that we do know about their close relatives, we see that there’s a lot of ecological variation in those close relatives through early dinosaurs, so all of that makes it hard to say what’s a dinosaur versus what’s a close relative now.”
