There had been no conclusive evidence supporting the existence of Allosaurus in Mid-Cretaceous Antarctica at the time this episode was made; it was merely based on an ankle bone found in Australia, which had been close to Antarctica in prehistoric times. A decade later, though, a carnivorous dinosaur (named Australovenator, or "Southern hunter") was described by scientists, whose parameters just about matched those of the carnivore in this episode. Thus it is not unreasonable to assume the "Allosaur" in this case is in reality an Australovenator, with a fairly accurate representation to boot, considering it wasn't known at the time of the production.
None of the creatures depicted in this episode have been found on Antarctica, but at the time Antarctica was connected to Australia. Thus, it is feasible that they also existed on the nearby Antarctica or migrated there during its warm summer. Only one genus of dinosaur has been discovered on Antarctica itself: the Early Jurassic theropod Cryolophosaurus. Since this was an 8 m long predator, it seems likely other, as of yet undiscovered dinosaurs also existed on Antarctica at the time.
Recent scientific finds have made palaeontologists re-evaluate the image of Leaellynasaura, the main dinosaur star of this episode. Its tail was actually much longer than what we see in this episode, taking up 75% of the animal's full length. What more, the animal may have been covered with a fluffy plumage.