Megalosaurus

Megalosaurus was the first Dinosaur to be discovered ever. Sir Richard Owen described it as a large monitor lizard due to its teeth that look so similar. The face of Megalosaurus remains a mystery,Dr,Thomas.R.Holtz says it might be a ancestor of the spinosaurids many scientist agreed with him while others say its a carnosaur. The most complete skeleton which has 22 percent of Megalosaurus had more details of a spinosaurid than a carnosaur. Megalosaurus might be 34 ft long, weighed 4 tons and might be a spinosaurid or ancestor.

More real-life information: Megalosaurus at Wikipedia.

Jurassic Park
Megalosaurus has never appeared or metioned in any jurassic park films or books, it has however appeaerd in Jurassic Park III: Park Builder.