Oneirosaurus

Oneirosaurus had a unique feature: two holes in its skull for nerves X, XI, and XII to exit, a trait not seen in any other plioplatecarpine mosasaur.1

Its name means 'dream lizard,' because the scientists who described it thought finding such a complete fossil was like a dream.1

Oneirosaurus lived during the Coniacian stage, about 89.8 to 85.7 million years ago, in a shallow sea that covered what is now Colombia.2

The only known fossil of Oneirosaurus is a nearly complete skull with a lower jaw and a disarticulated atlas (the first neck vertebra).2

Oneirosaurus belonged to a group of mosasaurs called Plioplatecarpinae, which were medium-sized, fast-swimming predators.2

Its teeth had two sharp edges (carinae) arranged 180 degrees apart, perfect for slicing through flesh.2