When climbing down into Mammoth Cave National Park, it's hard to imagine encountering anything connected to the ocean. But researchers have discovered shark fossils deep inside one of the Kentucky caves. The findings included a section of a jaw, many teeth and cartilage of 10 different shark species.
The remnants of the sharks are believed to be from the Late Mississippian Subperiod, a geologic time period within the Carboniferous period. They believe the fossils are at least 330 million years old.
With the help of paleontologist John-Paul Hodnett, national park researchers documented more than 100 shark specimens in the caves.
Teeth from Saivodus striatus, a prehistoric shark, have been found in the cave. (Photo: John-Paul Hodnett/Mammoth Cave National Park)
The jaw and several other pieces uncovered in the caves were part of a fossilized shark's head from the species Saivodus striatus.
This type of shark was only previously known to exist from fossilized teeth. The researchers say the discovery will help add important anatomical information that can help to understand how this ancient shark lived and how it was related to other sharks.
Researchers estimate the shark to be 16 to 20 feet long, roughly the size of a modern-day great white shark.
In addition, the discovery of cartilage within the fossils is particularly rare; cartilage is softer than bone and isn't always preserved over time.
Officials at Mammoth Cave National Park have known about the shark fossils for years, but they hadn't scientifically documented until now.
The National Park Service now knows more about the abundance, significance and rarity of the fossils, and they think this is just the beginning.
"There's hardly ever any any record at all of sharks teeth coming from these rocks. So that was exciting," Hodnett told CNN. "So this is a brand new record of sharks from a particular layer of time."
Scientists will continue to study the fossils, many of which are still lodged in the cave's rocks. Reaching the discovery site requires a quarter-mile crawl for a human, so maneuvering proper equipment to dig out more fossils more may be a challenge.
"We literally just scratched the surface, and the sharks are just coming out from that scratch," Hodnett told CNN. "So, hopefully, with more field work, we'll get another good batch of specimens to kind of help get at least some more rich diversity."
Researchers plan to present the preliminary findings in October at a meeting of the Society of Vertebrate Paleontology.