When paleontologist John Moretti snorkeled into Bender’s Cave — a shallow subterranean stream just north of San Antonio — he wasn’t prepared for what the cave floor looked like. “There were fossils everywhere, just everywhere, in a way that I haven’t seen in any other cave,” he later said. “It was just bones all over the floor.”
The cave had been flagged by a local spelunker who simply wanted to know what he’d found. But among the dozens of Ice Age remains were two creatures that, according to everything scientists thought they knew, had no business being in Central Texas at all.
A cave floor carpeted with bones
It started with a simple question. Spelunker John Young was snorkeling through Bender’s Cave in 2023 when he noticed the streambed was littered with bones. He photographed what he found and sent the images to paleontologist John Moretti, expecting a quick identification — and Moretti, stunned by the sheer density of fossils visible in the photos, knew immediately he had to see the site himself.
What followed was the first paleontological study ever conducted in a Texas water cave. Between March 2023 and November 2024, Moretti and Young returned six times, wearing goggles and snorkels to collect specimens from the streambed. Their findings were published in the journal Quaternary Research.
Familiar Ice Age residents — and two that shouldn’t have been there
Many of the fossils fit neatly into the established picture of Central Texas during the Ice Age. The cave yielded ground sloth claws, bones from saber-toothed cats, and mastodon remains — the mammoth-like creatures that once roamed the region’s dry grasslands alongside large grazing animals.
Then came the surprises. Shell fragments from a giant tortoise and bony armor from a pampathere — an armadillo relative roughly the size of a lion — turned up among the remains. Neither species had ever been documented in Central Texas before. That absence wasn’t an oversight: for much of the Ice Age, the region’s dry grassland environment simply wouldn’t have supported these animals, making their presence genuinely difficult to account for.
A warmer window roughly 100,000 years ago
Researchers have a working hypothesis. The fossils may date to an interglacial warm period approximately 100,000 years ago, when global temperatures temporarily rose and the regional ecology shifted into something more hospitable for tortoises and pampatheres. After the animals died, flooding events likely swept their remains through sinkholes and into the cave’s subterranean stream.
Pinning down precise dates has proven difficult. The mineral-rich stream water eroded the collagen proteins that scientists typically use to determine a fossil’s age. The team is now analyzing calcite crusts that formed on the fossils — a method that won’t yield a precise date but could establish a reliable minimum age for when the remains entered the cave.
Rewriting the ecological history of Central Texas
The implications reach well beyond two unexpected species. “We’re looking at a picture that’s different than the one in textbooks,” Moretti told Texas Monthly. “We’re opening a new window into the natural history of Central Texas.”
David Ledesma, a scientist not involved in the study, echoed that view. In a statement from the University of Texas at Austin, he noted that “some of the fossils that John has come across are species that we didn’t think would occur in this part of Texas,” adding that finding new things in a region considered well-studied is “quite exciting.”
One of the most pressing open questions is whether the tortoise and pampathere actually shared the landscape with the saber-toothed cats and ground sloths, or whether they lived thousands of years earlier during a separate ecological window. The answer would determine whether Central Texas once hosted a far more diverse interglacial community than previously imagined — or whether these animals represent an entirely distinct chapter in the region’s prehistory. Either way, the discoveries serve as a reminder of how much remains unknown about past ecosystems, even in areas studied for decades.
What comes next underground
Dating the calcite crusts is now the team’s primary focus. If those results confirm an interglacial origin roughly 100,000 years ago, the cave would offer a rare, direct look at an animal community never before observed in this part of Texas. “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 said.
Bender’s Cave may also be just the beginning. Texas has hundreds of water caves, and until now none had been the subject of a formal paleontological study. If one snorkeling trip by a curious spelunker could yield a giant tortoise and a lion-sized armadillo relative, the question follows naturally: what might be waiting in the others.