Prognathodon Fossils Shows Mosasaurs Were Converging with Ichthyosaurs

Sea monsters lying in wait for unsuspecting prey sounds scary enough. But slap on a tail that let them run down their dinner—much like today's great white sharks—and mosasaurs could truly be considered one of the ancient world's nightmares.

And that's exactly what a new study published September 10 in Nature Communications has confirmed.

A 72-million-year-old fossil specimen of Prognathodon—a genus of mosasaur—found in a Jordanian quarry in 2008 revealed fin-like soft-tissue imprints along its tail. Those imprints demonstrate that this group of ancient sea monsters possessed powerful tails similar to ones seen on sharks today, rather than the puny ones on eels or sea snakes.

Mosasaurs were aquatic reptiles that prowled the seas and freshwater streams toward the end of the age of dinosaurs, about 98 to 66 million years ago.

link.