Diplodocus was a large sauropod dinosaur that lived in Late Jurassic North America. It could have reached a length of up to 27 metres or even beyond. They weighed between 11 and 15 or so tonnes.
Diplodocus was the main dinosaur in Episode 2: Time of the Titans. The episode chronicles the journey of a young female from hatchling to adult. They face several dangers, including predation by Ornitholestes when less than a few minutes old as hatchlings, and when older, Allosaurus is shown attacking them in packs. They also face a devastating forest fire, and join a herd of adult Diplodocus.
Diplodocus also appears in The Ballad of Big Al, again as a prey item for Allosaurus. Its main appearance was when Big Al was an adolescent, when he and a few other Allosaurus made a loosely formed pack and attacked a Diplodocus herd. They singled out a sick victim, and waited until the heat (and its illness) killed it. However, Big Al attacked prematurely, before the great herbivore's strength failed, and was promptly knocked to the ground by the powerful neck of the Diplodocus.
In Sea Monsters - A Walking With Dinosaurs Trilogy, Diplodocus was one of the animals on Nigel Marven's time line.