Pelagic neonatal fossils support viviparity and precocial life history of Cretaceous Mosasaurs

If you’ve seen Jurassic World then you know that the scariest ancient dinosaurs were those giant swimming marine lizards – Mosasaurs. But what about their babies? Were they as cute as a puppy? New work by Aaron Leblanc (Reisz Lab) and his Yale and Smithsonian collaborators published in Paleontology sheds light on the youngest of Mososaurs. Mosasaurs swam in all of the world's oceans during the Late Cretaceous Period. They had big paddles for steering and powerful tails for propulsion. Aaron and his colleagues described the remains of two skulls of tiny Mosasaurs from Kansas that were collected over a century ago and were misidentified as bird fossils. They reinterpret them as baby Mosasaurs, based on dental and jaw anatomy. The presence of baby mosasaurs in open ocean sediments, coupled with the high level of aquatic adaptation led them to conclude that they gave birth to live young in the open ocean and did not come ashore to lay eggs. Mosasaurs were therefore much more similar to modern whales in their life history compared to sea turtles, because they spent their entire lives at sea.