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Geoscience’s Michelle Stocker finds fossils of worm-lizard that lived 40 million years ago

February 29, 2016

Virginia Tech researcher in West Texas
Michelle Stocker on site in the Devil's Graveyard Formation in West Texas.

A new species of an extinct, tiny worm-like lizard – dating back some 40 million years ago when the world’s climate was far different – has been found in rural West Texas, and given a nickname befitting its one-time home: Solastella, Latin for Lone Star.

The description of the fossil was made by Michelle Stocker, now a research scientist with Virginia Tech’s Department of Geosciences, part of the College of Science, during her doctoral studies at The University of Texas at Austin’s Jackson School of Geosciences. The fossil was discovered in 2011.

Fossil of new worm species discovered in West Texas
The skull of the Solastella cookei, found in the Devil's Graveyard Formation of West Texas.

The new species of worm lizard, known in the scientific community as an amphisbaenian, is the first known example of its kind found in Texas and points to the Southwestern United States as a subtropical refuge during one of the Earth’s great cooling periods. Findings on the fossil, of which only the skull survives intact, were published online last week in the Journal of Vertebrate Paleontology. The species’ full name is Solastella cookei, with the second part of the name in honor of botanist William Cook, a professor at Midwestern State University in Wichita Falls, which owns the property where the fossils were located.

“Nothing has been called Solastella before, which is amazing to me because there are so many fossils from Texas,” said Stocker. “It’s the one guy, and it’s from the Lone Star State, so it just seemed to fit.”

Stocker identified Solastella as a new species by analyzing fossilized skulls that she unearthed as part of a team in the Devil's Graveyard Formation of West Texas. The lizard is thought to have lived during the late Middle Eocene, a geologic period roughly 40 million years ago that supports the hypothesis that Texas served as a subtropical refuge for species that found it difficult to survive during the cooling climate. Solastella, similar to its modern relative, the Florida worm lizard, or Rhineura floridana, had no arms or legs, and used its head to burrow.

Solastella was small, its skull not much larger than the size of a pea. Details about its life are unknown. “There isn’t very much information on amphisbaenian life history,” added Stocker. “From what I’ve seen, some live to be about 15 years old, but there’s not enough data to know whether that would apply to all amphisbaenians or just a subset.”

Amphisbaenians, as with all reptiles, are cold-blooded, so maintain their body temperature to the external environment. This notion gives scientists a better sense at what the climate was like from reptiles than from mammals. In addition to Solastella, other reptiles also were found at the Devil's Graveyard site.

Teaming with Stocker on the paper was Chris Kirk, a professor of anthropology at The University of Texas at Austin who has conducted paleontological fieldwork in the Devil's Graveyard Formation for two decades. In the paper, he and Stocker noted that the presence of a variety of primate fossils in the same ground layer formation as Solastella also supports the idea that Texas was once a refuge in a cooling climate.

“Primates are generally tropically adapted mammals that prefer warm climates,” Kirk said. “The diverse primate community from the Devil’s Graveyard Formation is another indicator that the Big Bend region of Texas was warm, equable and forested during the late Middle Eocene.”

Stocker said the discovery gives insight into how certain animal groups could respond to climate change in the future. “With climate change, animals either adapt, or they move, or they go extinct,” she said. “And so we can look at what’s happened in the past and see that certain conditions caused certain things to happen in certain groups. The great thing about the fossil record is that the experiment has already been done for us. We just have to collect the evidence.”

The study was funded by The University of Texas at Austin and the Society of Vertebrate Paleontology.

Monica Kortsha, of the University of Texas at Austin, contributed to this story.

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