The film revolves around the lives of North American dinosaurs in the late Cretaceous period, through the eyes of an early mammal trying to survive.
The film provides examples of:
- Adult Fear: The mammal is has to survive not only for herself, but her offspring as well.
- End of an Era: As the dinosaurs die off, the mammal emerges to dominate the Earth.
- Family-Unfriendly Death: Despite being aimed at children, the short contains some surprisingly violent scenes.
- First, when the mother Triceratops catches the Ornithomimus eating her eggs, she impales it on her horn. The poor creature screams and writhes in agony as it dies, at which point the Triceratops scrapes the corpse off.
- Later, after failing to takes down an Ankylosaurus and a mother Triceratops, the Tyrannosaurus bites and suffocates an Edmontosaurus, though the actual eating is cut away from.
- Getting Crap Past the Radar: Besides the above mentioned death scenes, the first scene with the herd of Edmontosaurus shows the courtship of two individuals, where the male is explicitly shown about to mount the female. However, the arrival of the Tyrannosaurus stops them before anything can happen.
- Gory Discretion Shot: While the actual killing is shown in all its glory, the scene fades to black before the Tyrannosaurus can actually start eating the Edmontosaurus.
- Kill 'Em All: This being the end of the Cretaceous period, only the mammal is left standing by the end of the film.
- Mama Bear: The mother Triceratops not only successfully fights of a Tyrannosaurus attack, but she also kills an Ornithomimus trying to eat her eggs (the mammal avoids the same fate by scurrying off before she can be spotted).
- Spiritual Predecessor: To Prehistoric Beast, another stop-motion short about life in the late Cretaceous.
- Stock Dinosaurs: While the mammal doesn't seem to represent any species in particular, instead being some kind of generic rodent, the dinosaurs all belong to familiar genera.