The reptiles evolve, and the race for survival continues on land. Giant arthropods lurk in the Carboniferous forest, and sail-backed mammal-like reptiles fight for the survival of their young in the Permian.
Did You Know?
The giant spider that appears in the first segment of the episode is referred to as "Mesothelae", which is although not a proper name of a specific genus or species, the series tends to refer to a number of animals by the name of the animal group they belong to. Originally, this Mesothelae was meant to be a Megarachne, possibly the biggest spider ever discovered, until during the series' production, it turned out that "Megarachne" wasn't a spider at all, but an eurypterid (or sea scorpion). By this time, though, since the production was already underway, all they could do was to change the name of the spider. The error was not fixed completely, though, as (now that Megarachne has been re-classified) there is no evidence of any spider being as large as the "Mesothelae" depicted in this program. See more
As the female Dimetrodon starts eating the Edaphosaurus carcass, she leans ever so slightly backwards. Then she lowers her head again, but this motion follows the exact same pattern as the backwards-leaning motion - the animation is simply reversed, creating a slightly odd effect. The other parts of the animal, like her tail, continue in their motion, so only the animation used for the head has been reversed. See more
Even the air is alien. Over a third is oxygen, much higher than at any time in Earth's history. This oxygen-rich atmosphere has fueled the growth of new, super-sized arthropod predators.