Two hundred and thirty million years ago, the seasons in what is now Wyoming were dramatic. Torrential rains lashed the region for months, and when the mega monsoon ended, the region became extremely dry. This weather would have been challenging for amphibians that need to keep their skin moist, but a group of salamander-like creatures have found a solution, as their bizarre fossils show.

In a new study in the journal Proceedings of the Royal Society BResearchers describe a new species of fossil amphibians that were preserved in torpedo-shaped caves where they waited out the dry season.

“Based on how the rocks in the area formed and what they are made of, we can say that Wyoming experienced some of the most drastic seasonal effects of the mega-monsoon that affected the entire supercontinent of Pangea,” says Cal So, the study’s lead author and a new postdoctoral fellow at the Field Museum in Chicago.

“So how did these animals stay moist and avoid dehydration during the hot, dry season that lasted several months? That’s the cool thing. “We find these fossils in these cylindrical structures up to 12 inches long, which we have interpreted as caves.”

Cal So, who recently received his Ph.D. has acquired. from George Washington University, first encountered the strange fossil caves as an undergraduate at the University of Wisconsin, working with research scientist David Lovelace of the University of Wisconsin Geology Museum.

In 2014, Lovelace was searching for fossils in Wyoming, in an area managed by the Bureau of Land Management, in a layer of rock he would later call the Serendipity Beds.

“One of my passions is ichnology – the hidden biodiversity that can be revealed through animal tracks or traces of other living organisms,” says Lovelace.

He discovered a small cylindrical structure and several larger ones made of stone that looked “like a Pringle can.” Lovelace recognized that the structures were filled burrows created by an animal long ago, but one small specimen stood out.

“It was tiny, it was so cute,” he says. He collected several of the cylinders for his research.

Back in the lab, Lovelace went to one of the preserved caves with a hammer to see if there were any fossils in it and found a tiny, toothy skull.

“I saw sharp, pointy teeth and my first thought was that it was a baby crocodile,” says Lovelace. “But as we put everything together and prepared it, we realized it was some kind of amphibian.”

Lovelace turned to Jason Pardo, a postdoctoral fellow at the Field Museum who specializes in fossil amphibians. He took high-resolution CT scans of another fossil burrow and revealed a tiny skeleton inside.

“At that point we thought, ‘Oh my God, we have something really cool,'” Lovelace says. “I went back to put together the geological history of the site and then we found these caves everywhere. We couldn’t find her; the site was ridiculously congested.”

On one of his return trips, he sent So, who was a student at the time, to collect more caves. Ultimately, the team collected around 80 fossil burrows, most of which contained skulls and bones of ancient amphibians. These bones contained clues to the animals’ lifestyle. No complete skeletons were found, but based on partial remains they were probably about a foot long. They had tiny, underdeveloped arms, but researchers believe they had another way of digging their burrows.

“Their skulls have a sort of shovel shape. So we think they used the head to push their way underground at the bottom of a riverbed and go through a period of lower metabolic rate so they could survive the dry season. This is similar to what some modern salamanders and fish do,” says So.

Essentially, ancient aquatic amphibians spent the rainy part of the year swimming in rivers, but when those rivers dried up, they burrowed headfirst into the muddy riverbed. They spent the dry season underground, in a state resembling hibernation, until the monsoon returned a few months later and rainwater replenished the rivers.

The fossils found by So and Lovelace were simply unlucky because the paths of rivers changed from year to year. The places where these animals burrowed were no longer kept moist, so the animals never came out and instead died in their burrows.

The ancient amphibians lived in what are now the homelands of the Eastern Shoshone people, with whom the researchers maintain an ongoing collaboration.

“Our interest is in education, so we met with the Tribal Historic Preservation Officer for the Eastern Shoshone and he connected us with the schools,” Lovelace says. “It was a great cross-generational collaboration. We invited seventh grade students from Fort Washakie School, their teachers and elders to the field with us. The elders shared with us their understanding of the rocks and their history on the land. The students had to find caves and bones.

The middle school students are learning the Shoshone language and worked with elders to find a name for the Shoshone fossil amphibian: Ninumbeehan dookoodukah.

In their paper, the researchers explained: “’Ninumbee’ is the name for the mountain-dwelling Little People, who (among others) occupy an important place in Shoshone culture; -han is the possessive affix indicating affiliation with the Ninumbee, ‘dokooo’.” “means “meat” and “dukah” means “eater.” Overall, “Ninumbeehan dookoodukah” means “carnivore of the little people,” a tribute to the little people and a nod to the fossil’s sharp teeth. Our intention is to pay tribute to the Eastern Shoshone people, their language and the land to which they belong.

“The collaboration between our school district (Fremont County School District #21) and Dr. “Lovelace and his team illustrate the reciprocity in action and the long-term, transformative impact that can come from building authentic relationships between researchers and communities,” said Amanda LeClair-Diaz, coordinator of the Office of Indian Education and co-author of the paper.

“This process of bringing together scientists, community members, educators, middle school students and Eastern Shoshone elders to learn more about these fossils and choosing a Shoshone name for the fossil, Ninumbeehan dookoodukah, solidifies the intergenerational connection that we as Shoshone people as our homeland” and the beings that exist in this environment.

Ninumbeehan offers scientists a tantalizing clue to what life was like in Wyoming 230 million years ago. “Small amphibians are really rare in the Triassic, and we don’t know why that is,” says Pardo. “We find some big ones, but these little ones are really pretty hard to find.”

The newly described amphibians could also shed light on how modern amphibians might fare under the extreme weather conditions of the climate crisis.

“The diversity of modern amphibians is under significant threat, and climate change is a big part of that,” says Pardo. “But the way Ninumbeehan was able to slow its metabolism to wait out the dry weather suggests that some lineages of modern amphibians that have similar seasonal behavior may allow for greater survival than some of the models suggest. This is a small glimmer of hope.”