Long before humans appeared on the planet, dinosaurs ruled the earth. On a little off-coast island, a clan of lemurs finds a dinosaur egg, hatching. Since there are no parents, the lemurs take care of the newborn, Aladar. Years later, a medium meteor goes down close to the island and the shockwave forces its inhabitants to flee to the continent. There, Aladar and his family meet other dinosaurs for the first time as well as real dangers. The destruction caused by the meteor here has also forced a herd of different herbivores to move to a remote valley that can provide food and protection against the carnivorous predators following after. Since Aladar grew up with a different understanding of the ways of the world, his way of helping others first isn't accepted within the herd, but soon it is proven that reason may be better than panic.

The backgrounds in the movie are actually superimposed photos of exotic tropical locations such as Tahiti and Hawaii.

Plio:
[narrating] Some things start out big, and some things start out small, very small. But sometimes the smallest thing can make the biggest changes of all.

Incorrectly regarded as goofs: Many scenes contain grass. Grass didn't evolve until the early Cenozoic era, shortly after the dinosaurs died out. However, recent discoveries indicate that grass did, in fact, exist in at least the Cretaceous period. Naturally, according to science at the time of the production, it was still incorrect.