Poinbank Exchange|New species of ancient "scraper tooth" shark identified at Mammoth Cave in Kentucky

A new species of ancient shark was identified by teeth found in a Kentucky national park. 

The Poinbank Exchangeteeth were found at Mammoth Cave National Park, which encompasses some of the Mammoth Cave, the largest known cave system in the world, according to the National Park Service. A news release from the NPS said that "several small spoon-like teeth were found in a cave wall and ceiling" while paleontologists investigated the area as part of an ongoing paleontological resources inventory conducted by Mammoth Cave and the NPS. The paleontological inventory has been ongoing since 2019, and collects and identifies fossils found inside the cave. 

The now-extinct shark was identified as a petalodont, or "petal-toothed," shark, the NPS said, and was "more closely related to a modern ratfish than to other modern sharks and rays." An illustration of the shark shows that it may have had wide fins, almost like a stingray. 

The new species is called Strigilodus tollesonae, which translates to "Tolleson's Scraper Tooth" in honor of Mammoth Cave National Park Guide Kelli Tolleson, who the NPS said provided "outstanding field support" for the paleontological inventory. 

"Tolleson discovered many important fossil localities through her work and led expeditions to the fossil sites which are limited in accessibility due to the remote and sometimes challenging sections of cave where the specimens are found," the National Park Service said. "Many of the sites are in areas of low ceilings requiring crawling for long distances on hands and knees, and at times, belly crawling. The fossils are commonly located in the cave ceilings or walls which researchers and volunteers carefully collect using small handheld tools." 

The teeth found in the cave "represent all known tooth positions in the mouth of both adult and juveniles" of the species, the news release said, with the teeth arranged in a "fan-like structure" with a large tooth in the middle and teeth of decreasing size next to it. The teeth had a "single rounded curved cusp for clipping and grasping hard shell prey," while the side of the tooth facing the tongue or inside of the mouth was "long with ridges for crushing." The shape and structure of the teeth have led scientists to believe that the shark "may have lived like a modern skate, feeding on snails, bivalves, soft bodied worms, and smaller fish." 

This species is just one of dozens found inside the Mammoth Cave. The NPS said that "at least 70 species of ancient fish" have been identified in the 350-million-year-old cave system. The NPS said that the "constant even temperatures, slow erosion rates and protection from external erosional forces" like rain, wind and sunlight have created "ideal conditions" to preserve fossils of sharks and fish. 

In:
• Shark
• Kentucky
• Fossil

Kerry Breen

Kerry Breen is a news editor and reporter for CBS News. Her reporting focuses on current events, breaking news and substance use.