Show Details

Pregnant Pleisiosaur

August 29, 2011

A pregnant reptilian fossil clears up a long-standing paleontology mystery.



A prehistoric pregnancy at sea. I’m Bob Hirshon and this is Science Update.

Giant marine reptiles called pleisiosaurs ruled the oceans during the time of the dinosaurs. But scientists have long debated whether they bore young at sea or laid eggs on land. A 78-million-year-old fossil of a pregnant plesiosaur now on display at the Natural History Museum of Los Angeles County appears to have resolved the question. This according to Marshall University paleobiologist Robin O’Keefe.

ROBIN O’KEEFE (Marshall University):

The first time I walked up to it I literally got chills. Most of the mother is complete, it’s really well preserved and there’s this baby in it.


In contrast, many reptile species lay large numbers of eggs and leave the young to fend for themselves. But by bearing one large baby at a time, pleisiosaurs would have had to make a big parental investment, suggesting that they may have been social species. O’Keefe says it’s even possible that the giant predators lived in groups similar to orca whale pods today. I’m Bob Hirshon, for AAAS, the science society.