Long-Necked Sea Reptiles Had Unexpected Diet, Fossils Show

October 6, 2005

The fossilized last meals of two giant marine reptiles show the ancient animals used their long necks to trawl for clams, snails, and crabs along the seabed, according to a new study.

The discovery, based on the remains of two plesiosaurs unearthed in Queensland, Australia, challenges the long-held idea that these impressive ocean predators targeted only fish, squid, and other free-swimming prey.

Study co-author Alex Cook, assistant curator of fossils at the Queensland Museum, says the team was surprised by the fossilized sea creatures' last meals, eaten between 100 and 110 million years ago.

"Throughout the stomach region [of one specimen] were bits of broken clam and snail shell," Cook said. "There was also a fossilized food mass from the intestine, which was basically a solid lump of broken shell.

"This elasmosaur wasn't bothering much with fish—it was feeding almost entirely on bottom-dwelling mollusks."

The other elasmosaur's stomach contained crab and crustacean fragments.

Writing in tomorrow's issue of the journal Science, the Australian study team says the animals' varied diet could help explain why plesiosaurs were so successful. The predators prowled the Earth's oceans for some 135 million years before going extinct with the dinosaurs.

"Multipurpose Tool"

The two new specimens, each measuring 16 to 20 feet (5 to 6 meters) long and weighing around 2,200 pounds (1,000 kilograms), are from the elasmosaur family. These plesiosaurs had the longest necks of all—more than twice the length of their body and tail put together.

The bizarre-looking creatures became the inspiration for the Loch Ness Monster myth.

Colin McHenry, a biology lecturer at the University of Newcastle, New South Wales, describes the elasmosaur's extraordinary neck as a "multipurpose tool" for catching both free-swimming and seabed-burrowing prey.

"These were the dominant marine reptiles for 135 million years," he said. "The idea that the long neck was a generalized feeding tool is consistent with this success—specialized forms rarely last long.

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