Ancient Shark Species That Looked Like Stingrays Discovered in Earth's Largest Cave System

The largest cave system on Earth features fossils of an ancient shark species that resembled stingrays, a first-time discovery for the area.

The Largest Cave System on Earth

The world's largest cave system, Mammoth Cave National Park in Kentucky, is home to a shark species that was previously unknown.

The system, which has a length of more than 400 miles and is found in the state's south-central region, has several substantial underground channels. The Mississippian epoch, or 359 to 323 million years ago, when the supercontinent Pangea was growing, is when the rocks of the system were formed. The area of land that is now Kentucky was then south of the equator and was largely covered by shallow tropical seas.

The exceptional preservation of prehistoric shark fossils in the Mammoth Cave system is a result of the environment-specific setting. Sharks, rays, and skates are among the over 100 species of ancient cartilaginous fishes that have been discovered there.

The St. Louis Formation, St. Genevieve Formation, Girkin Formation, and Big Clifty Sandstone are the oldest to youngest of the several layers of Mississippian rocks that make up the Mammoth Cave system. The most diverse collection of extinct sharks is found in the older St. Louis and St. Genevieve formations.

Ancient Shark Species

The ancient shark species Strigilodus tollesonae was recently identified within the St. Genevieve Formation at Mammoth Cave National Park, dating back to approximately 340-320 million years ago. These findings were made during an ongoing paleontological resources inventory (PRI) project, led by Mammoth Cave Park officials and the NPS Paleontology Program, on National Fossil Day.

Strigilodus tollesonae is a petalodont, an extinct cartilaginous marine fish group found in the United States and Europe. This discovery is significant as it marks the first new shark species found at Mammoth Cave.

Park Superintendent Barclay Trimble expressed excitement about this achievement, acknowledging the dedicated efforts of geologists, paleontologists, park staff, and volunteers working tirelessly within the cave since the PRI project commenced in 2019. Their work not only unveils the historical richness of the area but also aids in comprehending the importance, distribution, and management of the fossil record within Mammoth Cave.

This remarkable discovery adds to our knowledge of prehistoric sharks, contributing to a broader understanding of the region's geological history.

Shark Looks Like a Stingray

Researchers have discovered that Strigilodus tollesonae is more closely linked to current ratfish than other sharks and rays.

The shark's teeth that have been discovered so far cover every potential tooth location in both the adult and juvenile forms of this species' mouths. The teeth appeared to be arranged in a fan-like pattern. The fossils' properties suggest that the shark may have had a diet similar to that of modern skates, which includes snails, bivalves, soft-bodied worms, and smaller fish.

The name of the shark is derived from the Latin phrase "Tolleson's scraper tooth". The species was given Kelli Tolleson's name in recognition of her contribution to the PRI as a Mammoth Cave tour guide.

The Mammoth Cave Park, a designated UNESCO World Heritage Site, contains several significant fossil sites that Tolleson unearthed, many of which are inaccessible. To reach them, researchers occasionally have to crawl through awkward gaps for considerable distances.