Giant salamander fossil reveals deep roots of Appalachian diversity

A single fossil of a giant Appalachian salamander has been discovered by scientists at East Tennessee State University.

Millions of years ago, this 16-inch salamander with a powerful bite threaded its way through the soft earth of what is now northeastern Tennessee.

The salamander tunnels criss-crossed ancient forests, and its appetite likely shaped the mix of smaller amphibians in the surrounding ecosystems.

Fossil may explain salamander diversity

Today, the fossil of this new species may help explain how the region’s salamanders became so diverse. The specimen surfaced at the Gray Fossil Site & Museum, a dig next door to East Tennessee State University (ETSU).

After careful study, researchers described the animal – Dynamognathus robertsoni – in a publication in the journal Historical Biology.

The work comes from a team that includes assistant collections manager Davis Gunnin, professor of geosciences Dr. Blaine Schubert, head curator Dr. Joshua Samuels, museum specialist Keila Bredehoeft, and assistant collections manager Shay Maden.

“Our researchers are not only uncovering ancient life, they are modeling the kind of collaboration and curiosity that define ETSU,” said Dr. Joe Bidwell, dean of the College of Arts and Sciences.

“This exciting find underscores the vital role our university plays in preserving and exploring Appalachia’s deep natural history.”

Species named for its powerful jaw

Dynamognathus robertsoni ranks among the largest of the lungless salamanders from the family Plethodontidae. It exchanged gases through its skin and the lining of its mouth, rather than by means of lungs.

The jaw anatomy of the ancient salamander suggests a striking bite force, which would have made it a formidable predator.

“This group of salamanders has unusual cranial anatomy that gives them a strong bite force, so the genus name, Dynamognathus – Greek for ‘powerful jaw,’ is given to highlight the great size and power of the salamander compared to its living relatives,” explained Maden.

The species name honors Wayne Robertson, a longtime volunteer who spotted the first bone and has sifted through more than 50 tons of sediment since 2000.

Appalachia’s surprising salamander legacy

Today, the Southern Appalachian forests host more than 50 salamander species – about one-eighth of all known salamanders on Earth.

Many of them are plethodonts like the new fossil species. Scientists have long wondered how so many species could have arisen in this small corner of the world.

“Finding something that looks like a Red Hills salamander here in East Tennessee was a bit of a surprise,” Gunnin said.

“Today they’re only found in a few counties in southern Alabama, and researchers thought of them as a highly specialized dead-end lineage, not particularly relevant to the evolution of the dusky salamanders.”

Evolution of salamander communities

The discovery of Dynamognathus robertsoni in Southern Appalachia indicates that this type of relatively large, burrowing salamander was once more widespread in eastern North America, explained Gunnin.

He noted that this may have had a profound impact on the evolution of Appalachian salamander communities.

Modern dusky salamanders max out at about seven inches (18 centimeters) – less than half the length of the fossil giant. The research team suspects that predators like D. robertsoni drove smaller stream-dwellers to diversify rapidly, setting the stage for today’s variety.

“The warmer climate in Tennessee 5 million years ago, followed by cooling during the Pleistocene Ice Ages, may have restricted large, burrowing salamanders to lower latitudes, like southern Alabama, where the Red Hills salamander lives today,” said Samuels.

Significance of the salamander fossil

“The latest salamander publication is a testament to this teamwork and search for answers,” said Schubert.

“When Davis Gunnin, the lead author, began volunteering at the museum as a teenager with an interest in fossil salamanders, I was thrilled because this region is known for its salamander diversity today, and we know so little about their fossil record.”

From high-school volunteers to seasoned faculty, the Gray Fossil Site team keeps uncovering stories buried beneath Appalachian soil.

The stories explain why a walk through a modern Tennessee stream still reveals more salamander shapes and colors than almost anywhere else on Earth.

This shared effort blends curiosity, dedication, and local pride in a way that brings science to life. With each new find, the team adds another piece to the puzzle of Appalachia’s ancient ecosystems.

The full study was published in the journal Historical Biology.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–