A team led by scientists at The University of Texas at Austin has described the first known Jurassic vertebrate fossils in Texas
The discovery has filled a major gap in the state’s fossil record as the weathered bone fragments are from the limbs and backbone of a plesiosaur, an extinct marine reptile that would have swum in the shallow sea that covered what is now northeastern Mexico and far western Texas about 150 million years ago.
The bones were discovered in the Malone Mountains of west Texas during two fossil hunting missions led by Steve May, a research associate at UT Austin’s Jackson School of Geosciences Museum of Earth History.
Before the discovery, the only fossils from the Jurassic period that had been collected and described from outcrops in Texas were from marine invertebrates, such as ammonites and snails.
May said that the new fossil finds serve as solid proof that Jurassic bones eexist in Texas.
He said: “Folks, there are Jurassic vertebrates out there!
“We found some of them, but there’s more to be discovered that can tell us the story of what this part of Texas was like during the Jurassic.”
Jurassic life
The Jurassic was an iconic prehistoric era when giant dinosaurs walked the Earth. The only reason we humans know about them, and other Jurassic life, is because of fossils they left behind.
But to find Jurassic-aged fossils, you need Jurassic-aged rocks.
Because of the geological history of Texas, the state hardly has any outcrops from this time in Earth history.
The 13 square miles of Jurassic-aged rocks in the Malone Mountains make up most of those rocks in the state.
In 2015, when May learned while researching a book that there were no Jurassic bones in the Texas fossil record, he decided to go to the Malone Mountains to explore.
He said: “You just don’t want to believe that there are no Jurassic bones in Texas. Plus, there was a tantalising clue.”
The clue was a mention of large bone fragments in a 1938 paper on the geology of the Malone Mountains by Claude Albritton, who later became a geology professor at Southern Methodist University (SMU).
It was enough of a lead to get May and his collaborators out to west Texas to see for themselves. Large bone fragments are what they found. The plesiosaur fossils are eroded and broken up.
But it’s a start that could lead to more science, said co-author Louis Jacobs, a professor emeritus at SMU.
Jacobs said: “Geologists are going to go out there looking for more bones.
“They’re going to find them, and they’re going to look for the other things that interest them in their own special ways.”
Other specimens
Today, the Malone Mountains rise above the dry desert landscape. During the Jurassic, the sediments were deposited just below sea level probably within miles of the shoreline.
The team found several other specimens that provide a glimpse into the ancient shallow marine environment, such as petrified driftwood filled with burrows from marine worms and the shells of clams, snails and ammonites.
The researchers also found a range of plant fossils, including a pinecone, and wood with possible growth rings.
Globally, Jurassic plant fossils from lower latitudes close to the Earth’s equator are relatively rare, said co-author and palaeobotanist Lisa Boucher, the director of the Jackson School’s Non-Vertebrate Paleontology Lab.
She said the plant finds should make the Malones a place of interest to other palaeobotanists and those interested in paleoenvironmental reconstruction.
Scientists have been conducting research in the Malones for over a hundred years. So, why did it take so long to bring back Jurassic bones?
May has several ideas – from the remoteness of the area and permitting, to the research interests of past scientists.
Whatever the reasons, Boucher said that the team’s discovery of a Texas first shows the value of fieldwork – simply travelling to a place to see what’s there.
She said: “It’s frequently part of the scientific process.
“There’re a few lines buried in an old publication, and you think ‘surely somebody has already looked at that’, but often they haven’t. You need to delve into it.”
The study is published in Rocky Mountain Geology.
Image 1: An artist’s interpretation of a Jurassic plesiosaur. Fossils from a plesiosaur discovered in west Texas are the only fossils from a Jurassic vertebrate found and described in the state. The University of Texas at Austin led the research. Credit: dibgd/Wikimedia commons. (CC0).
Image 2: The Malone Mountains of west Texas. Texas has very few outcrops of Jurassic rocks. Most of them are in the Malones. Credit: Joshua Lively.
