The 4.7 metre fossil contained an embryonic skeleton with little ribs, 20 vertebral disks, shoulders hips and paddle bones. It was previously thought that these 20 tonne giants hauled themselves up onto a beach or safe ledge and layed eggs in a fashion similar to turtles. Scientists have long suspected that the large creatures, which once were among the top predators in the world's oceans, were not built for climbing on land and laying eggs, but had no evidence to show otherwise until now.
Several other types of aquatic reptiles from the same Mesozoic period have been known to give birth to live offspring instead of eggs, a behavior that lends itself to a more social lifestyle, similar to that of dolphins.'Many of the animals alive today that give birth to large, single young are social and have maternal care,' added O'Keefe. 'We speculate that plesiosaurs may have exhibited similar behaviors, making their social lives more similar to those of modern dolphins than other reptiles.This fossil documents live birth in plesiosaurs for the first time, and so finally resolves this mystery,' said co-author Robin O'Keefe of Marshall University in Huntington, West Virginia.