Kentucky's Mammoth Cave National Park is a long way from the ocean, but newly discovered fossils suggest the area was once teeming with sharks.
Scientists have identified the remains of 15 to 20 different species of sharks deep in the cave, including part of the head of a great white-sized monster that's partially protruding from a wall, according to palaeontologist John-Paul Hodnett.
The sharks lived about 330 million years ago in what is known as the Late Mississippian geologic time period, when much of North America was covered by oceans.
When the sharks died, their remains were encased in sediment that eventually became the limestone where the cave formed.
"There's hardly ever any record at all of sharks teeth coming from these rocks," Mr Hodnett said.
"This is a brand-new record of sharks from a particular layer of time."https://www.instagram.com/p/B4d9dTZplWM/
Mammoth Cave scientists Rick Olson and Rick Toomey were mapping part of the cave when they started seeing shark fossils, according to Vincent Santucci, senior palaeontologist with the National Park Service.
Mr Santucci said the fossils were found in a remote part of the park that people can't visit without special permission, but they don't want to reveal the exact location.
Photos of their findings were sent to Mr Hodnett, because he's an expert on Palaeozoic sharks.
According to Mr Hodnett, there were a lot of shark teeth in the photos and said he also saw cartilage that might be a shark's skeleton.
"That's pretty rare because cartilage is softer than bone, so it's not often preserved," Mr Hodnett said.
When Mr Hodnett visited the cave in November, he realised he was looking at something much bigger.
"It turns out is actually not a skeleton, it is actually just parts of the head. And the head itself is pretty big," he said.
"You can see the part of the shark's jaw where it would have attached to the skull and the end that would have been its chin."
Some of the middle of the jaw isn't visible, but he estimated that it would have been about 76cm long.
The fossil was part of a species called Saivodus striatus that was about the size of a modern great white shark - about five to seven metres long.
Scientists don't know how much of the shark is still entombed in the rock.
"Caves are a very special environment, so it's not ideal to be removing big chunks of rock out of it and damage the internal environment by doing this," Mr Hodnett said.
Getting to this part of the cave is a challenge of its own, as the scientists had to crawl on hands and knees for about a quarter mile to reach the fossils.
Mr Hodnett estimates that he's found the fossils of about 150 different sharks from 15 to 20 different species.
Most of the fossil record from the Late Mississippian period was found in Europe, so this could answer a lot of questions about what was going on in North America.
"We literally just scratched the surface, and the sharks are just coming out from that scratch," Mr Hodnett said.
"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."
The researchers plan to present their preliminary findings in October at a meeting of the Society of Vertebrate Palaeontology.
Source: 9News https://www.9news.com.au/world/fossilised-shark-head-found-in-kentucky-cave/9bc8d90b-6db1-4604-9076-4ee4f6aaf5c7