These Snorkeling Scientists Stumbled Upon a Surprising Trove of Fossils in a Texas Water Cave

They found remains of animals that have never been uncovered in Central Texas. The fossils hint that the region was warm, moist and forested 100,000 years ago

Sarah Kuta | Daily Correspondent

April 1, 2026

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Roughly 100,000 years ago, during a relatively balmy period, giant ground sloths, saber-tooth cats, camels, mastodons, giant tortoises and lion-sized armadillo ancestors called a pampathere roamed what may have been moist, temperate forests of modern-day Central Texas.

This vivid picture comes from researchers who recently uncovered numerous fossilized animal remains in an underground stream near San Antonio. Several of the species had never been found in that part of Texas before, so their presence raises intriguing questions about the area’s climatic and environmental past. The discoveries were described in a paper published March 19 in the journal Quaternary Research.

Texas is home to thousands of caves, making it a hotspot for recreational and academic cavers. Many of these caverns contain well-preserved animal remains dating back tens of thousands of years, so they provide a window into the state’s prehistoric ecosystems.

A few years ago, study co-author John Young got permission to visit Bender’s Cave, a previously unexplored groundwater conduit system located on private property in Comal County just northeast of San Antonio. Once underground, Young—a spelunker and paramedic—began encountering a dizzying array of fossils.

“[Young] kept sending me photo after photo of bones he was finding in there, wanting to know what they were,” lead author John Moretti, a paleontologist at the University of Texas at Austin, tells Texas Monthly’s Asher Elbein.

His curiosity piqued, Moretti decided to join Young in Bender’s Cave. From March 2023 to November 2024, the duo made six trips into the cavern, which contains an underground stream. Although the water levels varied depending on recent rainfall, the stream was usually at least a few feet deep, so they donned snorkels, goggles and wet suits during their expeditions.

“We have bags attached to our waists, and we’re picking up fossils as we go,” Moretti tells Live Science’s Kenna Hughes-Castleberry.

In the end, they explored 21 different zones of the cave and recovered a wide array of fossilized remains, including bones, teeth, a giant ground sloth claw, giant tortoise shell fragments and bits of pampathere armor. The fossils were mostly scattered along the bottom of the stream bed in full view, though a handful were protruding from underwater mud.

“There were fossils everywhere, just everywhere, in a way that I haven’t seen in any other cave,” says Moretti in a statement. “It was just bones all over the floor.”

Researchers had previously discovered the remains of some of the animals in other caves throughout the region, including bison, horses, camels and mammoths. But some creatures that Moretti and Young identified were novel and completely unexpected, like the giant tortoise and the pampathere.

“Some of the fossils … are species that we didn’t think would occur in this part of Texas,” says David Ledesma, a paleontologist at St. Edwards University who was not involved with the research, in the statement.

The researchers suspect that the fossils were swept into Bender’s Cave through sinkholes during erosion and flooding events thousands of years ago, though they don’t know exactly when. They bear some physical similarities that suggest they were deposited at roughly the same time. But the lack of surrounding dirt, rock and other geologic materials, coupled with chemical changes to the fossils themselves from being submerged in mineral-rich water for so long, makes it difficult to precisely date them.

For now, the researchers’ best guess is that the animals were alive during a comparatively warm, interglacial period that occurred roughly 100,000 years ago. That’s based on knowledge of the preferred habitats of the now-extinct creatures. For instance, giant ground sloths and mastodons lived primarily in forests, while giant tortoises and pampatheres usually lived in places with hotter temperatures.

The Bender’s Cave fossils are also similar to known interglacial specimens discovered around Dallas and along the Gulf Coast.

Together, the findings suggest that Central Texas may have been relatively warm, wet and forested during interglacial periods. If confirmed, the discovery would challenge a long-held assumption that the region was an open, dry grassland and had a cool climate for most of the Ice Age.

“We’re looking at a picture that’s different than the one in textbooks,” Moretti tells Texas Monthly. “We’re opening a new window into the natural history of Central Texas.”

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Sarah Kuta is a writer and editor based in Longmont, Colorado. She covers history, science, travel, food and beverage, sustainability, economics and other topics.