Mosasaurs, prehistoric marine reptiles that could grow to the size of an 84-seat bus, were much speedier and shark-like than previously thought, an exceptionally well-preserved fossil specimen reveals.

The specimen is in such great shape that it includes soft tissue, according to a paper in the latest Nature Communications. That might open up the possibility of retrieving DNA and cloning the dinosaur-era animal.

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For now, scientists are focusing on how surprisingly similar mosasaurs were to sharks both then and now.

“Since both groups occupied similar ecological niches, being top-level carnivores, and lived in similar environments -- i.e., the open sea -- they gradually came to look like each other, so-called convergent evolution,” lead author Johan Lindgren of Lund University’s Department of Geology told Discovery News.

Sharks have existed for hundreds of millions of years, Lindgren said, while mosasaurs lived about 98 to 66 million years ago.

Lindgren and colleagues Hani Kaddumi and Michael Polcyn conducted a detailed analysis of the mosasaur individual, found in what is now central Jordan. The remains include the animal’s crescent-shaped tail and flippers.

These features, plus the mosasaur’s sleek overall body plan, reveal that the toothy predator was built for speed. Until this discovery, researchers thought the animals were not nearly as fast.

“Given that mosasaurs are lizards, they have traditionally been assumed to be lizard-like animals with long, serpentine bodies and paddle-shaped tails, which were capable only of short bursts of speed during brief ambush pursuits,” Lindgren said.

Stefan Sølberg

“However, our results clearly demonstrate that mosasaurs underwent the same kind of evolution as did the earlier ichthyosaurs and later whales -- that is, they gradually attained a streamlined body powered by a semiluminate tail fluke. This, in turn, suggests that at least the derived forms were pursuit predators and capable of high-speed swimming over long distances.”

Textbook illustrations of mosasaurs will likely change as a result of this latest research, since earlier drawings made them look more like eels or underwater snakes.

Students might also pay more attention to them in future, since researchers now have such a good fossil record for mosasaur evolution, with nearly every step documented. It’s a bit like looking at a hefty 1920s touring car and then seeing it gradually evolve into a streamlined speed machine.

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Being at the top of the food chain, large mosasaurs “were capable of handling virtually anything that came in their way.”

Whales emerged later, so they weren’t a threat. Evidence suggests mosasaurs did battle with sharks, however.

Frank O’Keefe, a Marshall University biologist, has also studied prehistoric marine life.

O’Keefe told Discovery News that the mosasaur ecosystem, aside from sharks, included plesiosaurs (another large now-extinct marine reptile), fish, squid, ammonites and other invertebrates. Mosasaurs might have also encountered toothed birds and pterodactyls, which often hung out near water, hoping for vulnerable prey.

O’Keefe said both plesiosaurs and mosasaurs went extinct about 66 million years ago, when dinosaurs also died out.

It is possible that mosasaurs dined on dinosaurs, but the meal likely would not have been tasty, or fresh.

“Dinosaurs lived on land," Lindgren said, "so the only chance of a mosasaur ever getting a bite out of one of those reptiles would have been a bloated and floating carcass that somehow ended up at sea.”