The depiction of Diplodocus with iguana-like spikes on its back was based on recent fossil findings showing impressions of such spikes preserved along with the bones. Post-2000 encyclopedias depict Diplodocus like this, as well. Though perhaps even this detail would become erroneous, as suggested by some recent studies made by palaeontologists. It could be that the spines didn't form a neat line over the animal's spine, but were arranged in a random pattern over its back.
The egg-laying method of Diplodocus- depositing eggs through a long fleshy ovipositor- as portrayed in this episode is not supported by fossil evidence. However, sauropods like Diplodocus were too heavy to crouch while laying eggs, and dropping eggs from several meters high would surely damage them. Thus, it's not unlikely an ovipositor-like appendage existed. The filmmakers based the concept on turtles, which also use a short ovipositor to deposit eggs.
Featured creatures in this episode: Diplodocus, Brachiosaurus, Stegosaurus, Allosaurus, Anurognathus, Ornitholestes, Dryosaurus (small bipeds seen throughout episode). The book also features the small Ornitholestes-like predator Coelurus.
Studies made after this show had been produced suggest that Sauropods actually had their nostrils on the front of their head. For the last couple of decades, they have mostly been pictured as having them on their "forehead" or on the top of their head, between the eyes. Thus, in a strange turn of fate, the older, outdated restorations are actually more correct than most of the newer ones in this respect. Another aspect of these animals that has been reevaluated is their neck-posture. According to the program, Diplodocus and related dinosaurs had stiff necks that they kept close to the ground. Scientists now say they held them at an angle of 45°.