Featured creatures: Smilodon, Doedicurus, Macrauchenia, Megatherium, Phorusrhacos.
The Macrauchenia sounds were actually those of a donkey.
The Megatherium sounds were actually low-pitched goat bleats.
The behavior of Smilodon was largely based on that of modern lions. Like the Smilodon in this episode, male lions lead the pride while the females do all of the hunting. Males roam alone in search of prides to take over, and when they succeed in doing so they will kill all cubs of the deposed leader. This causes the females to become fertile again, allowing the new leader to pass on his own genes and eliminate those of his predecessor.
The final clash between Half-Tooth and the Smilodon brother is the exact same piece of animation as the fight from the beginning of the story, only with the two fighting characters being switched up.