Mammoth Cave Yields Fifth New Shark Species In Fossil Record
Located in central Kentucky, Mammoth Cave is the world's longest known cave system with more than 400 miles (over 640 kilometers) of explored passageways… and counting! A UNESCO World Heritage Site and a U.S. national park, it's renowned for its vast subterranean network, as well as its unique geology and rich biodiversity. Formed over millions of years in thick limestone layers, the cave has served as a natural archive, preserving fossils and geological features that date back hundreds of millions of years. Above ground, the park's rolling hills, forested trails, and sinkholes offer a stark contrast to the silent, dark corridors below. Protected from wind, rain, and extreme temperatures, the cave's environment has acted as a natural vault for ancient remains until interested and determined minds unearth them. 'This finding not only enhances our knowledge of ancient marine ecosystems but also emphasizes the critical role of paleontological research in our national parks,' Trimble added. 'Every discovery connects the past with the present and offers invaluable educational opportunities for students and the public.'
The fossil was found in the Ste. Genevieve Formation (read more about the stratigraphy of the cave here), a rock layer buried deep within the cave and not accessible to the public. While the fossil was originally discovered back in 2020, it wasn't until now that scientists could confirm its identity as a distinct species. Unlike modern sharks with rows of replaceable teeth, Macadens olsoni had a whorl-like structure, which specialized for crushing, meaning it was likely a predator of small prey like mollusks and worms. Scientists believe Macadens olsoni grew to less than a foot in length (under 30 cm), making it more of a bottom-dwelling hunter than an apex predator. Though tiny by today's standards compared to some modern sharks, it was still an importnat part of a marine ecosystem that once covered what is now dry land. At the time, the region that would become Mammoth Cave lay under a shallow tropical sea that supported a variety of life, from corals and shelled creatures to early fish and, of course, sharks.
Mammoth Cave has emerged as a hotspot for ancient shark discoveries, with multiple species new to science identified within its limestone walls. Among them is Strigilodus tollesonae, a small shark named after cave guide Kelli Tolleson, known for its spoon-shaped teeth adapted for crushing shelled prey. Other finds include Glikmanius occidentalis and Troglocladodus trimblei, two species of ctenacanth shark fossils. With over 70 shark and fish species identified so far, Superintendent Barclay Trimble has said that, 'every new discovery at Mammoth Cave is possible due to collaborations.'
The name Macadens olsoni is a nod both to Mammoth Cave and to now-retired park scientist Rickard Olson, who played a vital role in documenting the cave's fossil record. Olson contributed heavily to the Paleontological Resource Inventory, the project that was launched in 2019 and aims to catalog and study the park's ancient biological history. This ongoing research is a collaboration between the National Park Service Paleontology Program, scientists at Mammoth Cave, and the Smithsonian's Paleobiology Department.
While many people visit Mammoth Cave to explore its vast chambers and underground passages for their sheer size and stunning beauty, few realize the sheer number of prehistoric secrets hidden in its walls. In fact, we don't truly know how many new-to-us species are waiting to be uncovered here. Thus, discoveries like Macadens olsoni are a great reminder that the land we walk on was once something entirely different… and that the history of life on Earth is often buried just beneath our feet. That's something worth digging into.
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