Aug. 7, 2013 at 1:56 PM ET
Waters off of France and the U.K. were once teeming with sharks, many of which would have looked like today's range of shark species.
Samples of Late Cretaceous rock from the region turned up remains of 96 different types of prehistoric sharks, 18 of which represent new species, a paper in the Journal of Systematic Paleontology reports.
The sharks lived from 100 million to 72 million years ago, but many looked like modern sharks.
"If you were to see a Cretaceous shark, I am pretty sure that it would look no different from one in an aquarium," senior author David Ward of The Natural History Museum in London told Discovery News. "Shark body design stabilized about 140 million years ago and, other than a few families that have suffered from extinction, remains the same now."
Lead author Guillaume Guinot, a researcher at the Natural History Museum in Switzerland, added that many of the identified fossil species have somewhat similar living representatives, such as today's angel sharks, carpetsharks, bullhead sharks, catsharks, cowsharks, dogfish sharks, sandtiger sharks and houndsharks. These are not direct relatives of the extinct sharks, however.
The Late Cretaceous sharks appear to have inhabited all sorts of water habitats off the coasts of what are now France and the U.K. Some sharks lived on or near the sea floor, while others actively hunted throughout the prehistoric seas. The largest sharks from the area at the time belonged to the genus Cretoxyrhina.
"This genus is also found in the Late Cretaceous seas of USA (the Western Interior Seaway) and probably reached 16.5 to 20 feet long and likely looked pretty much like the modern great white shark, although the two are not closely related," Guinot said.
Another big prehistoric shark from the region was Scapanorhynchus, which resembled a modern goblin shark and had a huge snout with enormous teeth.
It was a shark-eat-shark world then, with bigger sharks eating the smaller ones.
Ward shared, however, that giant marine reptiles known as plesiosaurs and mosasaurs, which looked a bit like underwater dinosaurs, were potential predators of sharks.
"It is difficult to distinguish between active predation and casual scavenging," Ward added. "Not having bone, sharks do not show bite marks."
Sharing the habitats with the ancient sharks were sea urchins, starfish, tube worms, lobsters, crabs, numerous other fish and many other animals. If the sharks got close to shore, they could have been chased by some of the enormous crocodiles that lived around 100 million years ago.
Sylvain Adnet, a paleontologist at Université Montpellier 2 -- CNRS, said that, since the Cretaceous study period was known to have had a warmer climate, the findings could reveal how sharks and their close relatives handle environmental changes, such as those taking place today.
Guinot, Ward and their colleagues Charlie Underwood and Henri Cappetta said that they have only scratched the surface in identifying prehistoric shark species. Guinot estimates that some 60 to 90 percent of all ancient sharks have yet to be identified.
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