Exquisitely preserved fossils of a shark that thrived through the Cretaceous interval seem to resolve a long-standing thriller round the way it hunted and the place it suits into the shark evolutionary tree.

Fossil enamel from sharks within the genus Ptychodus have made their means into museums for over 200 years, and whereas some members of this group clearly grew large, the remainder of their anatomy remained largely unknown.

This left researchers not sure in regards to the shark’s general look and feeding habits, though the broad, flat form of the enamel suggests they have been suited to crushing hard-shelled prey.

Now, Romain Vullo on the College of Rennes in France and his colleagues have reported the invention of six spectacular, full-body Ptychodus fossils in Mexico. They reveal that this shark belonged to the Lamniformes, a gaggle encompassing many fashionable shark species, starting from nice whites to basking sharks.

That is intriguing as a result of, no matter their food plan, lamniform sharks are usually extremely energetic predators that hunt in open water, not like any shell-crushing, or durophagous, organism alive right this moment.

“The particularity of Ptychodus is that it’s so far the one recognized open-water, fast-swimming shark with a durophagous food plan,” says Vullo. “This implies that ptychodontids preyed on well-armoured pelagic [open-water] organisms, akin to giant ammonites and sea turtles.”

Whereas the people they studied are small, at beneath 3 metres, the researchers estimate from tooth measurement that some members of the genus reached round 9.7 metres in size. That is roughly double the size of nice whites – the females are usually bigger and usually measure between 4.6 and 4.9 metres.

For a time through the Cretaceous, Ptychodus sharks have been actually quite a few, and are prone to have been key gamers in marine meals chains, says Charles Underwood at Birkbeck, College of London, but we knew subsequent to nothing about them till now. “It’s nearly the final jigsaw piece in placing collectively Cretaceous ecosystems,” he says.

Based mostly on their measurement and feeding habits, it’s potential that Ptychodus species have been in competitors with giant marine reptiles, which additionally developed crushing dentition through the late Cretaceous, says Underwood. This may increasingly assist clarify why Ptychodus sharks seem to have died out a while earlier than the end-Cretaceous extinction occasion that worn out the non-avian dinosaurs, he says.