Tylosaurus the Mosasaur

Tylosaurus was an enormous predator of the Cretaceous Period.  It has even been called "Sea Rex" ...which is the title of a very cool IMAX documentary.  A Tylosaurus from the movie Jurassic World was actually a lot oversized.  Still, Tylosaurus was probably 46-56 feet (14-15 m) long.  The very longest Mosasaur ever found was estimated to be 56 feet (17 meters) long.   Tylosaurus weight estimate of 15 tons or 30,000 lbs.  That would be 13.6 metric tons or 13,608 kg.  So Tylosaurus was longer and much heavier than the Cretaceous land top predator, T. rex.

Mosasaurs are NOT dinosaurs.  They are marine reptiles.  Dinosaurs were primarily land animals. Mosasaurs had live young and did not lay eggs.  They spent their entire life in the sea.

The first modern reported Mosasaur fossilized skeleton was found in a quarry in Holland in 1764, however, Native Americans had discovered many Mosasaur skeletons in North America long before that.

For years we thought that Tylosaurus had a sanke-like tail.  But now there is some controversy on the tail of Mosasaurs.  Recent findings have shown a tail fluke on some species of Mosasaurs.
Although this was found in some other species of Mosasar, not Tylosaurus, some paleontologist think, that based on the shape of the tail bones, we can infer that Tylosaurus had a tail fluke, and not the snake like tail.  That being said, Tylosaurus and all the Mosasaurs are closely related to modern snakes and monitor lizards.

Tylosaurus with Snake-like Tail

Tylosaurs with Tail Fluke