This is Halisaurus, a much smaller Mosasaur.
— Allen, about Halisaurus

Halisaurus (name meaning "Ocean Lizard") is a genus of mosasaur that originated during the Late Cretaceous period in what is now North America. At 4 meters long, it is a smaller mosasaur than Tylosaurus.

In the Series 2 finale, a single female Halisaurus, named Hali, was brought back to the park from the Late Cretaceous 65 million years ago. She resides in the Primeval Aquarium exhibit.


Era & DiscoveryEdit

Halisaurus lived in the seas during the Late Cretaceous period, 85–65 million years ago, alongside many other sea creatures, like Xiphactinus and Tylosaurus - the latter being the biggest known species and the top predator of the seas of that time. It died out with all marine Mesozoic animals, including the dinosaurs, at the end of the Cretaceous. It was first discovered by Othniel Charles Marsh in 1869.

Physical AttributesEdit

Halisaurus had the same overall physical appearance as larger Mosasaurs, like Tylosaurus. However, it was a relatively small Mosasaur, in fact, one of the smallest of Mosasaurs, reaching only 13 feet (4 m) long and weighing 500 lbs., making it much smaller than Tylosaurus.

Behavior & TraitsEdit

Halisaurus was a carnivore, specializing on coastal shelf ambush, hunting smaller prey items such as the still relatively large, 2-meter long Hesperornis. They were also sneaky creatures, keeping away from potential predators such as large sharks and other larger Mosasaurs like Tylosaurus.

It loitered in submarine caves and cracks and waited around ledges above the water where Hesperornis gathered, waiting in ambush near the coast for Hesperornis. Like all Mosasaurs, Halisaurus had the ability to open their mouths extremely wide, like snakes, and they swallowed their prey whole. Halisaurus was also a scavenger and fed upon the remains of others' kills, and small fish and ammonites.

When Hesperornis leave their rocky ledges to dive for fish, Halisaurus are down formations. And below, waiting for an opportunity to ambush them. Mosasaur teeth are good at piercing the skin of their prey but bad at slicing flesh. So once Halisaurus has caught its prey, it swallows it. Its jaw has flexible joints within it and can open incredibly wide.


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