U.S. researchers discovered a new shark species in rock layers at Mammoth Cave National Park in Kentucky,Ethermac Exchange the National Park Service reported.

On October 11, which is National Fossil Day, scientists found a new species of petalodont shark – a type of shark with petal-shaped teeth. This discovery was made in the Ste—Genevieve Formation rock layer at Mammoth Cave National Park, about 85 miles south of Louisville.

The new shark species, Strigilodus tollesonae, was discovered from spoon-like teeth found in a cave's wall and ceiling.

"We are excited to finally announce the discovery of our first new shark species at Mammoth Cave on (National Fossil Day)," said Mammoth Cave superintendent Barclay Trimble in a press release. "Teams of geologists, paleontologists, park staff, and volunteers have been hard at work deep inside the cave identifying and collecting fossils since the paleontological resources inventory began in 2019. Their important research allows us to better understand the scope, significance, distribution, and management issues associated with the fossil record found within Mammoth Cave."

In November 2019, John-Paul (JP) Hodnett, a shark fossil specialist working with the Maryland-National Capital Parks and Planning Commission, teamed up with the NPS Paleontology Program to identify the shark fossils in the park. This collaboration, known as the Paleontological Resource Inventories, aims to aid in managing non-renewable fossil resources within the national parks.

The species Strigilodus tollesonae is named after Kelli Tolleson, a guide at Mammoth Cave National Park who provided exceptional field support to the collaboration.

Tolleson discovered essential fossil sites in remote and challenging locations, according to the release. Access is limited due to the rugged terrain. The fossils are found in cave walls or ceilings and are collected using small handheld tools by researchers and volunteers who crawl long distances on hands, knees, and bellies.

Strigilodus tollesonae is an extinct species of shark that is more closely related to modern ratfish than to other modern sharks and rays. The teeth discovered at Mammoth Cave represent all tooth positions found in adult and juvenile specimens of this new species. The teeth were arranged in a fan-like structure, with a large tooth in the center and three smaller teeth surrounding it.

Strigilodus tollesonae had teeth with one rounded cusp for clipping and a long, ridged inner side for crushing prey. It probably fed on snails, bivalves, worms, and small fish, similar to modern skate fish.

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Mammoth Cave National Park plans to celebrate fossils found in the cave system with a series of presentations and exhibits on October 23 to highlight paleontology's scientific and educational value and the importance of preserving fossils.

What is Mammoth Cave National Park?

Mammoth Cave National Park is in Kentucky and has the world's most extensive cave system, over 400 miles long. Prehistoric people used it for shelter and resources.

Mammoth Cave was rediscovered by settlers in the early 1800s. It used to be a saltpeter mine until the end of the War of 1812. Today, it is a popular destination for guided tours.