Mosasaurus

Mosasaurus appears in Jurassic World as the first aquatic reptile in the films; earlier drafts of Jurassic Park III and the fourth film had used Kronosaurus instead. Director Colin Trevorrow suggested it as part of a feeding show in which guests in bleachers watch it leap from a lagoon to catch a shark hung above the water, before the seats are lowered for a view of its tank.

Trevorrow explained that the park had moved beyond mosquitoes for DNA, recovering it from iron in blood and bone, so the film did not have to explain how a mosquito bit a sea reptile. Legacy Effects made the original design, meant to echo Stan Winston's earlier dinosaurs, and ILM refined it, using crocodiles as reference for its swimming. It was first planned at 70 ft long, but Spielberg asked for it to be made bigger.