This Giant Salamander Once Hunted in the Hills of Prehistoric Tennessee

A giant salamander — one the biggest ever known to prowl the forests of ancient Appalachia — is offering new insight into the region’s remarkable amphibian diversity. Thanks to a fossil unearthed near East Tennessee State University (ETSU), scientists now have a clearer picture of how this prehistoric predator may have helped shape the salamander communities that thrive in the region today.

The newly described species joins the growing roster of remarkable finds from the university's Gray Fossil Site & Museum. The discovery was recently detailed in the journal Historical Biology by a team of researchers from ETSU and the museum.

In the lush Southern Appalachian forests, you're likely to cross paths with one of Tennessee’s roughly 50 salamander species, many of which belong to the family Plethodontidae, or lungless salamanders. As their name suggests, these amphibians breathe through their skin, a trait that limits them to moist environments.

Among the most common are dusky salamanders (Desmognathus), a diverse group found along the region’s cool mountain streams. Their variety reflects the rich biodiversity of the Appalachians.

In contrast, Alabama’s Red Hills salamander (Phaeognathus hubrichti), a rare lungless species with a worm-like body and tiny limbs, and which lives underground, is thought to be a more distantly related member of the same family. While both species lack lungs, they appear to have taken different evolutionary paths. The newly described fossil species may help connect those evolutionary dots.

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Named Dynamognathus robertsoni, this ancient creature was a giant compared to most of today's land-dwelling salamanders — about 16 inches long, roughly the size of a large pizza. For comparison, modern dusky salamanders max out at around seven inches. With an unusually robust skull, adapted for a strong bite force, the name Dynamognathus (Greek for “powerful jaw”) suits it well.

Described from Early Pliocene deposits dated to about five million years ago, Dynamognathus is believed to be either an ancient cousin or even a possible ancestor of today’s dusky salamanders.

It also shares a surprising resemblance with the modern Red Hills salamander, although its bones show features that modern dusky salamanders lack.

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

The discovery helps fill a longstanding gap in the fossil record between early lungless salamanders and their modern descendants. Researchers think that large, burrowing predators like Dynamognathus may have driven the rapid evolution of stream-dwelling salamanders in Appalachia by introducing new levels of competition and predation. These oversized desmognathans likely played a bigger role in prehistoric ecosystems than previously recognized.

The species name robertsoni pays tribute to Wayne Robertson, a longtime volunteer at the Gray Fossil Site who discovered the first fossil and has personally sifted through more than 50 tons of sediment since 2000.

Researchers suggest that climate shifts over time — warmer conditions during the Pliocene followed by Pleistocene cooling — likely forced large burrowing salamanders into more southern habitats, which could explain why their modern relatives are now limited to parts of Alabama.

“The latest salamander publication is a testament to this teamwork and search for answers,” said co-author and ETSU professor Blaine Schubert in the press release. “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. Thus, the possibility of finding something exciting seemed imminent.”

This discovery not only adds a new species to the fossil record, it also strengthens the case for Southern Appalachia as a hotspot for salamander evolution and diversity.

Read More: A Prehistoric Giant Salamander with Fangs May Redraw an Evolutionary Picture

Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:

• Historical Biology: A new plethodontid salamander from the Early Pliocene of northeastern Tennessee, U.S.A., and its bearing on desmognathan evolution

• Science Direct: Pliocene: an overview

Having worked as a biomedical research assistant in labs across three countries, Jenny excels at translating complex scientific concepts – ranging from medical breakthroughs and pharmacological discoveries to the latest in nutrition – into engaging, accessible content. Her interests extend to topics such as human evolution, psychology, and quirky animal stories. When she’s not immersed in a popular science book, you’ll find her catching waves or cruising around Vancouver Island on her longboard.