The Ornitholestes in this episode produce a different sound than in the original series. The sounds used in this special are actually the high-pitched noises that the Dromaeosaur made. The other dinosaurs retained their original sound effects.
The CGI Diplodocus (correctly) has a single claw on each of its front feet, the other four digits ending in stumps lacking claws. But the physical Diplodocus prop has sharp claws on each of its fingers.
Big Al's skeleton is shown to be in the University of Wyoming Geology Museum. Even Big Al's "ghost" appears next to it in the follow-up "behind the scenes" special. But the skeleton put on display is actually a cast. Big Al's real fossils are kept in Montana.
During the hunting scene on the salt planes, at around the 18:27 mark, the two Diplodocus tails on the left side of the screen are twisting in the exact same pattern, which in reality would be very unlikely.
The shadow of the first Allosaurus we see eating the Diplodocus is animated badly, since it doesn't come into contact with the large chunk of meat it's pulling around with its mouth. Later, when it is approached by the giant female, the movements of the meat don't correctly correspond to the way the animal drags it.
The feasting Allosaurus never cast a shadow on the Diplodocus carcass. The shadow of one Allosaurus actually goes underneath it. And when it lifts up the slab of meat in its mouth, the shadow of the meat seems to be floating on its own.
When the mother Allosaurus circles her nest, the bush behind her isn't disturbed even though her long tail should be touching it. If you look at the shadows, the shadow of the tail actually passes under the bush and reaches way beyond it.
In the establishing shot of the open environment, some Apatosaurus pass behind trees, but they aren't visible through the gaps between the tree's branches. You can see the background through the Apatosaurus.
When the female Allosaurus approaches the Stegosaurus carcass, her reflection in the water is visible through the reflection of the skeleton in front of her. But the skeleton's holes are not see-through, so the holes of its reflection shouldn't be see-through either.
When the Apatosaurus are walking across the forest edge, on the right side, one of them puts down its foot and a thin, light-colored area briefly appears around its foot. It disappears once it lifts its foot again.