The real species called Velociraptor was much smaller (about turkey-sized) than the animals in the film and were believed to have been feathered. They were part of bipedal, bird-like predators of the family Dromaeosauridae, some of which were even larger than the "velociraptors" in the film.
The scene where Grant, Tim and Lex meet the heard of Gallimimuses was scheduled to be the last scene shot on location in Kauai. When Hurricane Iniki hit, filming for this scene had to be postponed. Production returned to California and then, a few weeks later, Sam Neill, Joseph Mazzello and Ariana Richards had to travel back to Hawaii, but this time to the island of Oahu, to shoot the scene.
Although sickly in the film, a Triceratops could in reality battle a T-Rex.
Steven Spielberg considered Richard Dreyfuss for the role of Dr. Alan Grant.
The crew had to have safety meetings about the T-Rex; it weighed 12,000 pounds and was extremely powerful. They used flashing lights to announce when it was about to come on to alert the crew, because if you stood next to it and the head went by at speed, it felt like a bus going by.
The sound of the T-Rex killing Gennaro and a Gallimimus was Gary Rydstrom's Jack Russell terrier Buster, shaking a rope toy in his mouth recorded and slowed down because he thought a T-Rex would sound just like that. Buster also provided the sound for the T-1000 eye-spiking a prison guard in Terminator 2: Judgment Day (1991).
The T-Rex chasing the Jeep took some engineering. Paleontologists alleged a T-Rex could run up to 50mph. But the model was too big to run that fast, and its bones couldn't support its weight. So they dialed it down to a more acceptable 25mph. Hammond says it can go 32mph.
When the audience first saw the T-Rex, Steven Spielberg wanted it from inside the cars so the audience feels like they're experiencing it right there with the characters and feeling their fear.|