Paleontologists Discover Two New Shark Species From Fossils in Mammoth Cave National Park

Researchers have identified two new shark species from fossil discoveries in Kentucky’s Mammoth Cave National Park. The prehistoric fish are estimated to have lived more than 325 million years ago—predating the Pangea supercontinent, when all the major continents of today were lumped together into one giant landmass.

Paleontologists dubbed the new species Troglocladodus trimblei and Glikmanius careforum, the National Park Service announced last week. Both are thought to have been 10 to 12 feet long, about the size of a modern-day oceanic whitetip shark.

“These are active predators, really fast-swimming, catching other decent-sized fish, and in the case of Glikmanius, possibly even eating other sharks,” Rick Toomey, a cave guide and Mammoth Cave paleontologist, tells WBKO’s Derek Parham.

When these creatures lived, the region that is now Kentucky was an ancient seaway connecting North America, Europe and Northern Africa. Eons later, the strip of water got sealed off when the Earth’s tectonic plates rearranged, smashing the continents together into Pangea. Then, between 10 million and 15 million years ago, acidic rainwater began dissolving the limestone-rich ground to form the earliest shafts of the Mammoth Cave network, making the ancient rock beds accessible.

The world’s longest underground tunnel system, Mammoth Cave now stretches for more than 400 miles, with unmapped passageways still waiting to be discovered. The underworld of Mammoth Cave makes for an excellent environment to preserve fossils, as prehistoric materials housed within it aren’t exposed to the outside elements. As such, its fossils are often more intricate compared to those found on the surface that have undergone weathering.

“In such a stable environment, those things look like they just came out of the shark’s mouth yesterday,” John-Paul Hodnett, a paleontologist at the Maryland-National Capital Park and Planning Commission, tells Melissa Hobson of Live Science.

In the last 25 years, at least 70 species of prehistoric marine animals have been identified from fossils in the cave, and the two new shark discoveries add to that growing total.

Especially noteworthy, T. trimblei belongs to an entirely new genus. Researchers identified the species from adult and juvenile teeth in Mammoth Cave, as well as the Bangor Formation in Alabama. The early shark’s most notable features are its branched teeth that resemble tridents. The genus name reflects the shark’s curious dentures—Troglocladodus means “cave branching tooth.” The species label honors Barclay Trimble, the park superintendent for Mammoth Cave, who found the first fossil specimen of his eventual namesake in 2019.

The second shark, G. careforum, was identified from teeth located in Mammoth Cave and the Hartselle and Bangor formations in Alabama. But perhaps more tantalizingly, a partial set of jaws and gills of this species still rests within Mammoth Cave, too fragile for excavation. These fossils were lodged in a channel too tiny for the researchers to fit inside.

From the shape of the mandible, the team thinks the shark had a short head and a powerful bite that allowed it to chomp smaller sharks, bony fish and hard-shelled orthocones, the ancestors of squids. The age of these fossils push back the origins of the Glikmanius genus to 50 million years earlier than thought.

The two fossils were found in an area that’s off-limits to the public—only authorized researchers can enter. Even so, anyone who wants to reach the fossil site faces a challenge: To get to the spot where T. trimblei was found, “you have to crawl on your hands and knees for a quarter mile,” Hodnett tells Live Science. “And that hurts, for me, after a while.”

But the extreme conditions can make some fossil discoveries all the more serendipitous. T. trimblei was discovered entirely by accident—on the way to see the Glikmanius jaw fossil in 2019, superintendent Trimble stumbled upon a fossil embedded in the ceiling.

“He looked up and pointed and said, ‘Hey! Is that one of the shark’s teeth?” Toomey recounts to Spectrum News 1’s Aaron Dickens. Little did the paleontologists know that the tooth would eventually open up the field to an entirely new genus, the Troglocladodus. “We said, ‘Wow, that’s going to be a […] really interesting shark.’”

Shi En Kim | | READ MORE

Shi En Kim is a Washington, D.C.-based freelance science journalist. Her work has appeared in National Geographic, Scientific American, the Atlantic, Popular Science and others. In 2021, she interned at Smithsonian magazine as an AAAS Mass Media Fellow.