For most of her academic career, Michelle Stocker, assistant professor of geosciences at Virginia Tech, has dedicated her work to the study of vertebrate paleobiology. Stocker’s lecture Friday, Sept. 27, titled “Life after Death: Evolutionary Experimentation in the Aftermath of the Permo-Triassic Mass Extinction,” discussed two focuses of her scholarly work: phytosaurs and the convergence of species.
The lecture included visuals of prehistoric conceptions of the Earth, as well as skeletal images and data regarding a rare species known as the phytosaur.
“They are a group of archosaurs that are generally similar to crocodilians, but different in key ways,” Stocker said. “In a phytosaur skull, the nostrils are far more posterior and closer to the eyes, which is one major difference. We have a lot of skulls, but we don’t have a lot of post-cranial information because the skulls themselves are four feet long.”
The phytosaur began as a short-snouted, greyhound-like creature and morphed into a super-predator, equipped with a long snout resembling the modern crocodile and a bite force equivalent to that of a Tyrannosaurus rex. Scientists discovered rare complete skeletal fossils of the phytosaur at dig sites in the American Southwest, China and Tanzania. The late Triassic remains are massive, allowing paleontologists to study a small terrestrial creature’s evolution to a potentially semi-aquatic predator.
The discoveries made by Stocker and her fellow partners have been integral in forming a more complete understanding of the Triassic period. When asked how she first became interested in paleontology, Stocker explained that she took an introductory geology course at the University of Michigan, where she received her bachelor’s degree. During an eight-week field study in Wyoming, she realized she could combine her love of animals, science and research by pursuing paleontology.
“I loved being able to look at the landscape and understand how it got to be the way it was,” Stocker said. “Combining rocks and animals and getting to research them in the lab has been really interesting to me.”
“I loved being able to look at the landscape and understand how it got to be the way it was,” Stocker said. “Combining rocks and animals and getting to research them in the lab has been really interesting to me.”
Stocker also touched on her current research in Arizona, which she has worked on since 2014. For her research, Stocker excavates micro-fossil components of fauna of all body sizes during the late Triassic period to examine the period’s geology. Her research helped bridge the gap between the Prosalivus bitis, which is believed to be the first frog to ever jump, and the Triadobatrachus massinoti, a 250-million-year-old proto-frog. Commonly found in the American West in the Navajo Nation, the Prosalivus bitis is 185 million years old and dates to the early Jurassic period. In comparison, the Triadobatrachus massinoti existed during the early Triassic period and is found in Madagascar.
This large gap both in time and bio-geographical distance between the two morphologies of the amphibians left many questions for paleontologists. Knowing the origination of these groups enables speculation on the relationships and morphologies evolved and how certain behaviors came to be, like jumping.
At her dig site, Stocker discovered the ilium of a frog, which is used to identify the original animal. The dorsal processes on the hip bone shared features with early Triassic frogs, but was far more like the early Jurassic frogs. In conclusion, Stocker found an early representative of a Brachycephalus, a very small modern frog, that lived in the late Triassic period.
Now, her team has a search image and can identify the prevalent frog bones in other fossilized material in her dig site. That one small bone filled the chronological gap and shows frogs were in equatorial Pangea far earlier than once thought, and the fossil shows morphological transitions in frogs from tetrapods, when features originated and how they fit into the period with specific fauna — all of which have been influential in driving the field’s research further.
“Critical thinking is key in any aspect of anything. One of the things I try to teach the students in my class is that science presented in the news isn’t presented accurately. Science is a process that we are constantly updating our understanding on. Also, for them to know that stories can change as we get more information, and that is okay. It doesn’t mean we were wrong before, it just means we were saying something based on the data we had at the time.”
“You have to understand the data behind the things that we say,” Stocker said. “Critical thinking is key in any aspect of anything. One of the things I try to teach the students in my class is that science presented in the news isn’t presented accurately. Science is a process that we are constantly updating our understanding on. Also, for them to know that stories can change as we get more information, and that is okay. It doesn’t mean we were wrong before, it just means we were saying something based on the data we had at the time.”
The audience of the seminar included a mix of students and professors from both inside and outside the geology department. Tessa Keyser ’21 attended the event to learn more about the evolution of species and the traits that are carried through the morphology.
“I’m not a geology major, but I was interested in the convergence of species — it would go extinct but then another species would evolve in the same way,” Keyser said.
“I’m not a geology major, but I was interested in the convergence of species — it would go extinct but then another species would evolve in the same way,” Keyser said.
Another student, Jennifer Doran ’23, also attended the seminar out of pure interest. While she has no idea what her major will be, she immensely enjoys her paleontology class and wants to expand her knowledge of dinosaurs.
“My biggest takeaway was how recent some of the discoveries about the Mesozoic era are,” Doran said. “For so long paleontologists have researched dinosaurs and their existence, and only now are they discovering these other creatures that existed were really important to the ecosystem and provides a lot of contextualization for the life of dinosaurs.”
