Understanding Reptile Evolution
Oct. 19, 2022
SHSU Media Contact: Campbell Atkins
Former Sam Houston State University graduate student and current doctoral student in Yale University’s Department of Earth and Planetary Sciences, Kelsey Jenkins, authored a study with paleontologists from SHSU, Yale and the University of the Witwatersrand in South Africa that recently appeared in the Journal of Anatomy.
Jenkins was the lead author of the study, which helps fill in the gaps regarding the evolution of the 250-million-year-old reptile known as Palacrodon following the Permian-Triassic extinction event, which killed off 70 percent of earth’s terrestrial species and 95 percent of marine species. Her study also indicates that reptiles, plants and ecosystems may have recovered more quickly than previously thought following the catastrophic event.
This work is a result of tireless efforts from Jenkins as well as her SHSU MS thesis adviser Patrick Lewis, Jenkins’ PhD adviser from Yale, Bhart-Anjan Bhullar, Dalton Meyer of Yale and Jonah Choiniere of the University of Witwatersrand. It encompasses years of field research in areas such as South Africa, Antarctica and the American Southwest in an impressive collaboration effort.
Jenkins’ journey, meanwhile, all started when she came to SHSU as a graduate student under Lewis.
“I don’t think I really knew what it meant to be a scientist as an undergrad,” Jenkins said. “I was a science major at LSU, but I did not really know how research worked. Going to Sam, Patrick was willing to take a risk on me and I was able to get a lot of hands-on help from the faculty.”
Lewis, who was instrumental in Jenkins’ development as a scientist as well as her specific reptile research, described himself as a “proud parent” when contemplating how far she has come in the field.
“She was the graduate student of the year at SHSU, which is not easy for a master’s student,” Lewis said. “With grad students, I am always thinking about something that might get the attention of a bigger school and doctorate program. I felt good about sending her to a program like Yale.”
Before her acceptance to Yale, Jenkins was looking for a suitable master’s project while studying at SHSU.
“I have been working in South Africa since the late 90s, she came here from LSU knowing she wanted to work in Africa but did not have a group of animals she was focusing on,” Lewis said. “I said, maybe we can figure out what these Palacrodon jaws are, so that became the focus of her work.”
“Patrick was really a great adviser in getting me started and teaching me what a reptile was in that sense,” Jenkins said.
Their studies of early reptiles and, more specifically Palacrodon, brought Jenkins, Lewis and others to South Africa for further research. Jenkins first went to examine collections at the local museum in 2016 and then went with Lewis and their lab group in 2017.
Their travels took them to the Free State Province of South Africa, which contains rich soil and a pleasant climate, allowing for a thriving agricultural industry. The students would often board with local farmers, who were thrilled to host paleontologists in their homes.
“It is very grassy and dry with flat land but there are also these beautiful mesas and outcrop areas,” Jenkins said.
One of those outcrops included rocks that were over 240 million years old and produced tiny fossils that helped the paleontologists put together their ultimate puzzle, which Jenkins continued to build on after her Yale acceptance.
“When you’re doing a master’s project, you want something that’s a bit on the smaller side, something that is going to be compact and looking at one thing, or one animal, in my case,” Jenkins said. “Moving onto a PhD, I had to sort of broaden my horizons, so I’m not just looking at Palacrodon, but pretty much the entire group that we would call early reptiles.”
Palacrodon can be found across the world and is one of the last lineages to branch off the reptile tree of life before the evolution of modern reptiles. The Palacrodon specimen highlighted in their study is from Antarctica and was collected in an early paleontological expedition to the continent in the 1970s.
Although many reptile species eventually bounced back from the Permian-Triassic extinction event, the details of how that happened are murky. Researchers have spent decades trying to fill in the gaps in our understanding of key adaptations that enabled reptiles to flourish after the extinction and what those adaptations may reveal about the ecosystems where they lived.
At Bhullar’s lab at Yale, Jenkins used computed tomographic (CT) scanning and microscopy to analyze the most complete Palacrodon specimen, the fossil from Antarctica.
Using the technology, the researchers were able to obtain characteristics of the reptile’s teeth, as well as other physical features. It revealed that Palacrodon’s teeth were best suited for grinding plant material and that the reptile was likely capable of occasionally climbing or clinging onto vegetation.
According to Jenkins, the study points to a need for further examination of fossils from the time period just after the Permian-Triassic extinction event.
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