Newspaper article The Christian Science Monitor

How Ancient Sea Reptiles Transformed into Fierce Predators

Newspaper article The Christian Science Monitor

How Ancient Sea Reptiles Transformed into Fierce Predators

Article excerpt

Large reptiles were successful predators, snapping up fish, mollusks and smaller reptiles.

Ancient sea monsters had more than just sharp teeth and fearsome size on their side. They were able to chase down prey thanks to an even, warm body temperature that kept their muscles humming even in cold water, a new study finds.

Researchers analyzed fossilized teeth of three groups of reptiles that lived from 251 million to 65 million years ago in the Mesozoic era. The chemical makeup of the teeth differed subtly from those of cold-blooded fishes that lived during the same times and places, suggesting the reptiles retained heat like modern tuna and some species of shark (and unlike today's crocodiles and alligators).

"The only way to maintain a constant and high body temperature is that the animal is able to produce internal heat by its organs," said study researcher Christophe Lecuyer of the University of Lyon in France. "It was probably very useful for them to dive in deep waters to track prey and also to have access to environments where normal reptiles cannot go."

IN PICTURES: Monsters of the deep

The finding helps explain why these large reptiles - dolphin- shaped icthyosarus, sea lion-like plesiosaurs and elongated mosasaurs - were such successful predators, snapping up fish, mollusks and smaller reptiles. By maintaining a relatively warm body temperature, the biochemical reactions powering their muscles would have operated more efficiently.

Although the exact temperature of the animals is up for debate, Lecuyer and his colleagues peg them at between 95 degrees Fahrenheit (35 degrees Celsius) and 102 degrees F (39 degrees C), or in the range of modern dolphins and whales.

Researchers had already judged that icthyosaurs and plesiosaurs must have had a high metabolic rate because they have the body structure of "cruisers," swimming the ocean for food like sharks. Mosasaurs are thought to have been ambush predators, lying in wait for prey, which would have required less of an ability to regulate heat. The microscopic structure of the reptiles' bones also suggested they were different from typical reptiles.

In the new study, Lecuyer and his colleagues measured the ratio of two oxygen isotopes (oxygen atoms with different numbers of neutrons) in fossilized tooth enamel. …

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