Limbless, essentially sightless, it burrowed in the soil for a meal of insects or insect larvae. It was a lizard – but it looked like an earthworm.
In February 2016, paleontologist Michelle Stocker announced the discovery of a new lizard species in the Big Bend. She named it Solastella cookei – the “Lone Star Lizard.”
You won't find the lizard today. It made its home in West Texas 40 million years ago, when the land was lush and tropical, and when animal life as it exists today was just beginning to take shape.
Michelle Stocker is a research scientist at Virginia Tech University. Her PhD studies at UT-Austin took her to the Dalquest Desert Research Station, 60 miles southeast of Marfa. The site, straddling Presidio and Brewster counties, is owned by Midwestern State University, in Wichita Falls, Texas. It's a maze of rocky canyons and desert badlands.
At a canyon called the Devil's Graveyard, Stocker searched volcanic rock for fossils.
“It's this volcanic tuff, so it's very hard rock,” Stocker said, “but that means it preserves the fossils very nicely. So when we were out doing fieldwork, we'd find these as little nodules. And the way that we collect out there, you can't quite see what the bones are, in some cases, because they're not clean. You have to get them back to the lab and prepare that rock off of them, before you can really identify what animal it is or what part of an animal it is.”
Jaw bones, teeth, vertebrae – at the lab in Austin, Stocker used a needle or a small pneumatic drill to clean the fossils. She found mammal bones and the bones of snakes and other reptiles.
Among the fossils were tiny lizard skulls, less than an inch long. Stocker identified them as the skulls of an amphisbaenian, or worm lizard.
Worm lizards typically live in tropical environments. They're fossorial – living underground or in dense leaf litter. Only one species lives in the United States today, in Florida. Many are found in Central and South America, where they grow to four feet long or longer.
The fossils of extinct worm lizards have been also found in the northern U.S. Stocker compared her skulls to these American fossils and to living worm lizards.
“And we found enough differences to say, 'Oh, well it looks like it's something new,'” she said. “But there's also enough similarities that you can say that it's probably closely related to some of these other extinct forms, and to the one that's alive in Florida today.”
“Solastella” is “Lone Star” in Latin. Stocker said she was surprised no scientist had used the name before. She thought it was fitting for this new but ancient Texas creature.
What does the Lone Star Lizard tell us about prehistoric West Texas?
The fossils date to the middle Eocene Epoch – between 48 and 38 million years ago.
The Eocene was a dynamic period. After 135 million years of dominance, the dinosaurs were gone. Changes in climate had eliminated other species, too. With these resources freed up, the Eocene witnessed an explosion of new forms of life. Over a relatively short time, most of the mammals we know today made their first appearance, from marsupials and rodents to elephants and primates.
As the Eocene progressed, the planet began to cool. The new creatures had to adapt or perish.
Worm lizard fossils suggest migration may have been one way to do that. Older fossils are found to the north. West Texas remained warm and wet through much of the Eocene. The region could have been a sanctuary for worm lizards.
As man-made climate change intensifies today, Stocker said the fossil record provides clues about what will happen to present-day animals in the future.
“So comparing those climate changes in the fossil record to climate changes that are happening today, you can predict what may or may not happen with animals that are alive today,” she said.
The Dalquest site offers a unique window into the Eocene. It was a time of volcanic activity in West Texas, and the welded volcanic ash at Dalquest has kept these fossils intact. The volcanic strata here are well-defined, and geologists can distinguish time periods through the layers of rock. This allows fossils to be accurately dated.
And as the Lone Star Lizard shows, even a tiny fossil can tell a big story.