The final dinosaur Nigel encounters and the star of To Hell...and Back.
A large mosasaur that grew to immense size when compared to it's earlier kin. It had large teeth capable of piercing skin and swallowing it's meals whole. Due to their build they were very capable of defending themselves against rival dinosaurs.
In To Hell...and Back they were the final quarry of Nigel where he and possibly the crew were eaten.
- The Tylosaur, along with other mosasaurs, had fluke tails similar to sharks and other marine dinosaurs.