Scientists have uncovered a new fossil species of extinct shark hidden within the winding chambers of Mammoth Cave in Kentucky – the longest known cave system on Earth. The discovery published in the NPS Paleontological Resource Inventory report for Mammoth Cave National Park. The fossil reveals a highly unusual tooth structure that sets it apart from all known shark species. At that time, the area that now holds Mammoth Cave was submerged beneath warm, shallow waters rich in marine biodiversity. Revisiting A Familiar FossilAlongside the discovery of Macadens olsoni, researchers revisited another shark fossil originally known as Helodus coxanus.