Baryonyx

Baryonyx was a spinosaurid Theropod Dinosaur about 30 feet long that lived in the early Cretaceous of Britain, from 110 to 90 million years ago. It is famous for its crocodile-shaped skull, and huge hand claws for grabbing at fish.

In Jurassic Park
Baryonyx is seen only on the brochure map in Jurassic Park. It has never appeared in person, but there are rumors it may in the fourth movie. Also, the Spinosaurus in Jurassic Park III was originally going to be a Baryonyx.

Debate
Some Jurassic Park fans have argued that since Spinosaurus was scarcely known in the 90s, and since baby Spinosaurs have no sails, that Baryonyx does not exist in Jurassic Park, and was instead a misidentification of the Spinosaurus. The makers of the films have no comment.