Remains of extinct Jurassic marine reptile help to close Texas fossil gap

The weathered fossil pieces include an aquatic marine reptile's limbs and backbone. 
Mrigakshi Dixit
Steve May, a research associate at the Jackson School of Geosciences, holds a fossil from a plesiosaur.
Steve May, a research associate at the Jackson School of Geosciences, holds a fossil from a plesiosaur.

Jackson School of Geosciences/The University of Texas at Austin 

All we know about the lost Jurassic period is from the fossil remains unearthed from various parts of the world. These discoveries aid experts in piecing together a wide range of facts about dinosaurs and other creatures, including their evolution, migration, and adaptation to various habitats. 

Now, Jurassic fossils of an extinct marine reptile have been unearthed in Texas. This finding is immensely important as it contributes to filling the state’s fossil record gap.  

The team of scientists led by the University of Texas at Austin discovered bone fragments of plesiosaur that lived in the shallow sea of what is now northeastern Mexico and western Texas about 150 million years ago.

The fossil discovery

The weathered fossil pieces include this aquatic marine reptile's limbs and backbone. 

These were discovered in the Malone Mountains in West Texas. The Malone Mountains rise above the barren desert landscape, but there was a coastline here during the Jurassic era. 

Remains of extinct Jurassic marine reptile help to close Texas fossil gap
The Malone Mountains of West Texas. Texas has very few outcrops of Jurassic rocks. Most of them are in the Malones.

According to the official statement, before this finding, the only fossil record of this time period came from marine invertebrates (such as ammonites and snails) in Texas. 

The team now has "solid proof" that Jurassic bones can be discovered in Texas thanks to this newly uncovered specimen.

“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,” said Steve May, a research associate at UT Austin’s Jackson School of Geosciences Museum of Earth History, who led the excavation work, in an official release. 

Hard to find Jurassic-period rocks in Texas

It is necessary to identify Jurassic-aged rocks in order to find Jurassic-aged fossils. And Texas has only a few outcrops from this time frame due to its geological history. 

Most of these rocks are confined in the 13 square miles stretch of Malone Mountains. 

The quest to discover these Jurassic-era bones came into the mind of Steve May in 2015 while perusing a book that stated there were no Jurassic bone fossil records in Texas. 

“You just don’t want to believe that there are no Jurassic bones in Texas,” May said. 

While researching, May also got a good lead that mentioned large bone fragments in the Malone Mountains. That’s when he went on to explore the Jurassic-period rocks at Malone Mountains. 

The plesiosaur bones were found to be eroded and broken up. However, considering Texas's less well-known Jurassic rocks, the team feels it is a promising start. 

“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” said Louis Jacobs, the co-author of this new study. 

The findings have been published in the journal Rocky Mountain Geology

Study abstract:

We present the first description of Jurassic vertebrate fossils from Texas. The vertebrate specimens were collected from the Upper Jurassic Malone Formation in the Malone Mountains of western Texas. The specimens are fragmentary and not particularly diagnostic, but probably represent elements of plesiosaurians. One specimen is similar to the caudal vertebra of a pliosaurid plesiosaurian, whereas another may be a partial propodial of a small plesiosaurian. Additional bone fragments are not identifiable at this time. These vertebrates were discovered along with abundant plant and invertebrate fossils. Previous studies of the invertebrate fossils indicate a Kimmeridgian to Tithonian age for the Malone Formation, which is consistent with a single grain age of 151±2 Ma from detrital zircon U–Pb geochronology obtained in this study. The Malone Formation was deposited in shallow marine to marginal marine environments along the northern edge of the Chihuahua trough. It is correlative with the La Casita and La Caja Formations of northern Mexico, where similar marine vertebrates have been reported. The Malone Formation is also correlative with the Morrison Formation to the north.

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