Wearing a wet suit, goggles and a snorkel, palaeontologist John Moretti conducted the first ever palaeontological study of a Texan ‘water cave’, finding remains of animals thought to have lived more than 100,000 years ago.
The recent doctoral graduate explored a series of underground streams in Bender’s Cave, located in Comal County just north-east of San Antonio. From these streams, Moretti collected fossils from a giant tortoise, an armadillo relative (pampathere) the size of today’s lions, and several other Ice Age animals.
Texas is home to thousands of caves, many of which contain underground streams that serve as important passageways for groundwater across the state. A lot of these caves have been explored and anecdotally described by cavers as ‘rich in fossils’, but until Moretti’s recent study – published last month in the journal Quaternary Research – no thorough, palaeontological investigation of a Texan water cave had ever been conducted.
This dearth of studies inspired Moretti and co-author John Young, a local caver, to don their snorkelling gear and begin their investigations, starting with the previously unexplored groundwater conduit system of Bender’s Cave.
“There were fossils everywhere, just everywhere, in a way that I haven’t seen in any other cave,” said Moretti. “It was just bones all over the floor.”
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The bones are thought to have entered the cave through sinkholes that formed during erosion and flooding events that happened millennia ago, and they’ve remained there ever since.
Based on the composition of identified animals and their co-occurrence at other sites across Texas, Moretti believes the bones discovered in Bender’s Cave date to the last interglacial of the Late Pleistocene, a warm period that occurred roughly 100,000 years ago and preceded the last Ice Age. If this dating proves correct, these bones will be the first of their kind from this period found in Central Texas.
“This site is showing us something different, and that’s really important because of all the work that’s been done in this region,” Moretti said. “If it is interglacial in age, it’s a new window into the past and into a landscape, environment and animal community that we haven’t observed in this part of Texas before.”
Moretti and Young made six trips to Bender’s Cave from March 2023 to November 2024, collecting fossils from 21 different zones. The streams they sampled were never more than a few feet deep, though snorkelling gear was still necessary to identify fossils lying underneath the water’s surface.
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Other notable finds include a claw from a giant ground sloth and bones from sabretooth cats, camels and mastodons.
These remains, like those of the giant tortoise and armadillo relatives, were polished, rounded, and displayed a rusty red mineralisation. This is to be expected of fossils that have spent thousands of years tumbling along streams, and it suggests they were swept into Bender’s Cave at a similar time.
What makes Moretti’s findings particularly interesting are that they include completely unexpected species. David Ledesma, a palaeontologist at St. Edwards University who was not involved with the latest study, stressed this in an accompanying statement.
“Some of the fossils that John has come across are species that we didn’t think would occur in this part of Texas,” he said. “That we’re still learning new things and finding new things is quite exciting.”
Most of Texas’ unexplored caves are located on private property. In order to learn more about the prehistory of this important region, land owners and scientists must work together, forming partnerships that enable studies like those just conducted by Moretti.
Top image: Palaeontologist John Moretti searches for fossils in the stream that flows through Bender’s Cave. Credit: John Young
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