Researchers in Idaho say they've finally solved a mystery surrounding a 270-million-year-old shark. After a century of guessing, scientists have put a face to the giant animal that once swam the region, back when the Northwest was underwater.
The problem was that sharks are mostly made of cartilage, which doesn't keep well over millennia. So all scientists had from Helicoprion was a curious spiral of thin, serrated blades – which various scientists imagined to be from its dorsal fin, its tale - even it's nose.
“It's incredible how many ideas have been proposed," says Idaho State University geologist Leif Tapanila.
He says the answer turned out to be: teeth. Tapanila led the team that came up with an animal reminiscent of a great white shark - with a buzz saw in its mouth.
He says high-powered CT scans revealed the spiral of teeth was actually embedded in the creature's lower jaw – and that spiral kept growing, pushing older teeth down as new ones came in.
“No animal, to our knowledge, has ever or does do this," Tapanilla says. "This is ridiculous. But it works, it works for this animal. It lasted, as far as we can tell, about 10 million years.”
There was one more surprise. Technically, Helicoprion was not a shark at all. It's more closely related to the ratfish now found off the Pacific Coast.
The study is published in the journal Biology Letters.