Sharks in Kentucky? What Explorers Found in Mammoth Cave is Blowing Researchers' Minds

Thursday, January 30, 2020

During a trip to Mammoth Cave National Park in November, paleontologist John-Paul Hodnett was stunned.

Preserved in the walls of the cave were parts of a large, fossilized shark head — from a shark that lived about 330 million years ago. 

The discovery began when Mammoth Cave specialists Rick Olson and Rick Toomey came across the fossils as they explored and mapped the cave system. They sent photos to Vincent Santucci, the senior paleontologist for the National Park Service in Washington, D.C., for help identifying the fossils. 

Santucci then sent Hodnett, a paleontologist and program coordinator at Dinosaur Park in Maryland, to help with what became the "Mammoth Cave National Park Fossil Shark Research Project."

Some of the shark fossils in the photos were identifiable, but Hodnett said what got him really excited was something else.

"One set of photos showed a number of shark teeth associated with large sections of fossilized cartilage, suggesting there might be a shark skeleton preserved in the cave," he said. 

Researchers discovered fossilized remains of a 330-million-year-old shark in Mammoth Cave. (Photo: Provided by Matt Cecil)

Fossils of shark skeletons are rare because cartilage does not typically survive fossilization. Shark teeth, however, are made of bone and enamel and preserve well. Since sharks replace their teeth throughout their lives, shark teeth are one of the most common fossils on the planet, Hodnett said.

"I wasn't exactly sure what I was going to see in the cave during my trip in November," Hodnett said. "When we got to our target specimen my mind was blown."

The fossils weren't parts to a full skeleton, but parts of a head that belonged to a shark, about the size of a Great White Shark, which ranges in length from 11 feet to 21 feet.

Based on what was exposed in the cave wall, Hodnett said the find includes a lower jaw, skull cartilage and several teeth. Hodnett determined the shark belonged to a species called "Saivodus striatus" from the Late Mississippian period, about 330 to 340 million years ago. 

Hodnett said the time period is not well-represented in North America but is well-known in Europe.

"Most significantly, the majority of the shark fossils we discovered come from a layer of rock that extends from Missouri to Virginia but never documented the presence of sharks, until now," he said. "It's like finding a missing puzzle piece to a very big picture."

Thanks to the slow erosion of the limestone in the cave, the shark teeth are mostly intact and extremely detailed.

The back of the lower jaw of the Saivodus shark starts by the hand, and the front edge of the jaw sticks out at the opposite end. (Photo: Provided by John-Paul Hodnett)

More than 100 individual specimens have been discovered during the project. Hodnett said teeth and dorsal fins of other shark species are also exposed in the cave ceiling and walls. 

"We've just scratched the surface," Hodnett said. "But already it's showing that Mammoth Cave has a rich fossil shark record."

Because the National Park Service has experienced fossil theft and vandalism in the past, it does not release information about the specific location of fossils found in its parks.

"We want the public to benefit from the scientific information, but at the same time we have a duty to protect these non-renewable resources," Santucci said.

Hodnett said the team is working on presenting a preliminary account of the project in October at the Society of Vertebrate Paleontology meeting in Cincinnati.