The fourth episode of Prehistoric Planet, "Ice Worlds," takes viewers to the poles to explore the dinosaurs that would have experienced colder conditions than their compatriots. As seen since episode 1, one of this series' strongest points is the willingness to be conservative in identifying the animals, choosing to go with what we definitively know rather than potentially dating itself. More than any episode, "Ice Worlds" puts that to the test. The first animal we see is a dromaeosaur, a member of the group that includes Velociraptor. Prehistoric Planet doesn't go any further in identifying it, a point that might frustrate some viewers. There's a reason, though - much of the Arctic portion of "Ice Worlds" is based on the fauna of the Prince Creek formation in Alaska, which has a lot of animals that seem closely related to counterparts in the south, but the fragmentary nature of the fossils means it's hard to positively identify them. Is this dromaeosaur a Dromaeosaurus, or something new entirely? We don't quite know. A great example is the hadrosaurs of the Prince Creek formation, depicted in the episode's opening. They were initially identified as Edmontosaurus, which has been found in southern Canada and the northern United States. In 2015, the remains were assigned a new genus and species, Ugrunaaluk kuukpikensis. But then, in 2017 and 2020, new studies reassessed the fossils and determined they were indistinguishable from Edmontosaurus, although they weren't assigned to either of the two known species (annectens and regalis). Since this dinosaur's classification is up in the air, it makes sense to remain cautious in labeling it for the show. After this opening, the episode moves "further North" to a herd of Olorotitan arharensis. I'm not sure why the documentary says "further North" instead of just saying "northern Asia," as Olorotitan were discovered in the Udurchukan formation of Russia.
