Amphibian fossils found in burrows reveal ancient survival strategies 

Two hundred and thirty million years ago, in what is now Wyoming, dramatic seasonal changes dominated the climate. Torrential monsoons drenched the region for months, followed by extreme dry spells. Such harsh conditions posed significant challenges for amphibians, which rely on moist environments for survival.

However, a group of salamander-like creatures developed a unique adaptation to endure these extremes, as evidenced by their unusual fossils discovered recently.

A recent study describes a new species of fossil amphibian preserved in torpedo-shaped burrows. These ancient creatures apparently used these burrows to wait out the dry seasons, showcasing an early form of estivation – a state of dormancy similar to hibernation.

Seasonal survival strategies of amphibians 

Lead author Cal So, an incoming postdoctoral scientist at the Field Museum in Chicago, explains that Wyoming during the Triassic period experienced some of the most drastic seasonal effects due to the mega-monsoon impacting the supercontinent Pangea.

“How did these animals stay moist and prevent themselves from drying out during the hot and dry season that lasted several months?” So asked. “We find these fossils inside these cylindrical structures up to 12 inches long, which we’ve interpreted as burrows.”

The discovery traces back to 2014 when David Lovelace, a research scientist at the University of Wisconsin Geology Museum, was searching for fossils in a rock layer he named the Serendipity Beds.

Lovelace noticed cylindrical structures resembling infilled burrows and collected several for analysis. Upon examining one of the preserved burrows in the lab, he found a tiny, toothy skull.

“I saw sharp, pointy teeth, and my first thought was that it was a baby crocodile,” Lovelace recalled. “But when we put it all together and prepared it, we realized it was some sort of amphibian.”

Fossils reveal a new amphibian species

Collaborating with Jason Pardo, a postdoctoral researcher at the Field Museum specializing in fossil amphibians, the team conducted high-resolution CT scans of the burrows, revealing more skeletal remains. 

Recognizing the significance of their find, the researchers continued excavations and ultimately collected around 80 fossil burrows, most containing skulls and bones.

The partial remains suggest that these amphibians were about a foot long with tiny, underdeveloped arms. Their skulls had a scoop-like shape, indicating they likely used their heads to dig burrows into the muddy riverbeds during dry seasons.

“They spent the dry season underground, in a state somewhat similar to hibernation, until the monsoon returned a few months later,” So explained. 

Unfortunately, some of these creatures never emerged, possibly due to changes in river paths that left their burrows dry, leading to their demise.

The amphibians have been given a Shoshone name: Ninumbeehan dookoodukah, meaning “Little People’s flesh eater.” This name honors the Eastern Shoshone people and references the creature’s sharp teeth.

Eastern Shoshone community engagement

The fossils were discovered on lands stewarded by the Bureau of Land Management, within the ancestral territories of the Eastern Shoshone people. The research team established an ongoing collaborative relationship with the local community.

“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 said. 

Middle school students from Fort Washakie School, along with their teachers and elders, joined the researchers in the field. The elders shared their knowledge of the land, while the students assisted in finding burrows and bones.

Amanda LeClair-Diaz, Office of Indian Education Coordinator and a co-author of the paper, highlighted the importance of this collaboration.

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

Insights into amphibian survival

The discovery of Ninumbeehan dookoodukah offers valuable insights into life during the Triassic period. Small amphibians from this era are rare in the fossil record, making this find particularly significant.

“We find some big ones, but these small ones are really quite challenging to find,” Pardo said. The survival strategy of these amphibians – burrowing to escape extreme weather – mirrors behaviors seen in some modern species.

Understanding how ancient creatures adapted to climate extremes can inform current studies on how modern amphibians might cope with the changing climate. 

“The way that Ninumbeehan could slow down its metabolism to wait out the dry weather indicates that some lineages of modern amphibians that have similar seasonal behavior might allow for greater survivorship than some of the models suggest,” Pardo said. “It’s a little glimmer of hope.”

Looking to the past in hope for the future

The research not only uncovers a new species but also strengthens the connection between science and indigenous knowledge.

By integrating paleontology with community collaboration, the study enriches our understanding of Earth’s history and fosters appreciation for the intricate relationships between ancient creatures and their environments.

As climate change poses new challenges, the resilience strategies of Ninumbeehan dookoodukah may inspire hope and guide conservation efforts for present-day amphibians facing similar environmental pressures.

The study is published in the journal Proceedings of the Royal Society B.

Image Credit: Copyright: Gabriel N. Ugueto

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