Mosasaurs were born at sea, not in safe harbors
By Sid Perkins
From Norman, Okla., at a meeting of the Society of Vertebrate Paleontology
Mosasaurs were prehistoric aquatic reptiles that cruised the world’s oceans for 30 million years or so before they and the dinosaurs on land went extinct, about 65 million years ago. Newly discovered mosasaur fossils suggest that the creatures gave birth in midocean, countering previous theories that their first days were spent on or near shore.
The evidence comes from expansive chalk deposits in Kansas that have yielded fossils of at least 10 different mosasaur species since the late 1860s, says Michael J. Everhart, a paleontologist at Fort Hays State University in Hays, Kan. Large numbers of mosasaurs, which grew up to 15 meters long, inhabited a broad, shallow seaway that covered much of what is now North America’s Great Plains, says Everhart. The fossil-bearing chalk deposits were laid down as ocean-floor ooze hundreds of kilometers from the waterway’s shores.