Scientists have uncovered a previously unknown species of extinct shark deep within the labyrinth of Mammoth Cave in Kentucky — the world’s longest known cave system.
The species, named Macadens olsoni, measured under a foot in length and stood out due to its highly unusual dental structure. It was likely to have feasted on mollusks and worms.
Unlike typical sharks, this ancient predator had a distinctive set-up: a single row of teeth along each side of the jaw, with three prominent teeth positioned at the front — a formation unseen in any known shark species to date.
The fossil was unearthed from the Ste. Genevieve Formation, a rock layer dating back approximately 335 to 340 million years.
Its discovery was made possible by a collaborative team comprising experts from the National Park Service’s Palaeontology Programme, Mammoth Cave National Park, and the Smithsonian Institution’s Palaeobiology Department.
National Park Service
The name is a nod to both Mammoth Cave itself and Rickard Olson, a retired park scientist whose work was instrumental in cataloguing shark fossils during a recent Palaeontological Resource Inventory.
“This discovery is a remarkable addition to our understanding of ancient marine life and underscores the importance of preserving and studying our natural history,” Superintendent Barclay Trimble said.
“This finding not only enhances our knowledge of ancient marine ecosystems but also emphasises the critical role of paleontological research in our national parks,” he added. “Every discovery connects the past with the present and offers invaluable educational opportunities for students and the public.”
Alongside Macadens olsoni, researchers also reanalysed another ancient shark species, formerly known as Helodus coxanus. It has since been renamed Rotuladens — Latin for “wheel tooth” — in reference to its distinctive dental shape. The two species share notable characteristics, offering fresh insight into the rich variety of prehistoric marine life that once thrived in the region.
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