Plesiosaurs carried young like a mammal

Plesiosaurs — giant marine reptiles that ruled the oceans 75 million years ago — gave birth to single large babies and may even have nurtured their young, according to a new study. F. Robin O’Keefe, a paleontologist at Marshall University {{more}} in Huntington, W.Va., and Luis Chiappe, director of the Dinosaur Institute at the Natural History Museum in Los Angeles, teamed up to study the only known fossil of a plesiosaur mother and her unborn baby. The ancient relic is considered the first evidence that these aquatic behemoths gave birth in the water instead of laying eggs on land, the researchers reported online Thursday in the journal Science.

“It’s a really neat specimen,” said Mike Everhart, adjunct curator of vertebrate paleontology at the Sternberg Museum of Natural History in Hays, Kan., who was not involved in the study.

The fossil was discovered by amateur paleontologists Marion and Charles Bonner while hiking in northwest Kansas in 1987. They noticed flat bones sticking out of the shale; these turned out to be the mother plesiosaur’s pelvis. They continued digging and found the creature’s four flippers, ribs, hips, spinal column and part of its neck.

The Bonners had found many fossils before, but “I had an inkling that this was different,” Charles Bonner said. He and his father wanted scientists to study it carefully, so they sent the specimen to the Natural History Museum, where it sat in storage until recently.

In 2008, O’Keefe and Chiappe decided to take a closer look before showcasing it as part of the Los Angeles museum’s new Dinosaur Hall.

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