A Carnotaurus ambushes an infant Parasaurolophus triggering a stampede, which forces an Iguanodon mother to abandon her nest. The one surviving egg journeys through several predicaments via the flight of a pterosaur, before ending up on a far away island populated by lemurs. Plio names the hatched baby Aladar and raises him. Years later, Aladar and the lemurs take part in the mating ritual, where Zini goes without a mate. Moments after the ritual ends, a giant meteor strikes and destroy the island, spreading numerous exploding fireballs. Aladar, Plio, Zini, Yar and Suri flee and jump across the sea to the mainland. They mourn for their losses before moving on.
While crossing the deserted wastelands, they are ambushed by a pack of Velociraptors. After escaping, the family comes across a remaining multi-species herd of dinosaurs led by Kron and Bruton, who are on a journey to reach the "Nesting Grounds", a valley said to be untouched by the meteor. As Aladar and the lemurs befriend a trio of elderly dinosaurs (Brachiosaurus Baylene, Styracosaurus Eema and doglike Euoplocephalus Url), Kron permits them to follow the herd. Together, they migrate across the desert to a lake they have relied on for past trips. Though it has seemingly dried up by the meteor, Aladar and Baylene discover the buried water under the dried surface, saving the herd from dehydration. Impressed by Aladar's compassionate ways, Kron's younger sister Neera begins to fall in love with him.
Meanwhile, two Carnotaurus pick up the herd's trail and begin stalking them for food. Bruton and an Iguanodon Scout search for water, but are attacked by the Carnotaurs. Bruton escapes badly wounded, while the Scout is eaten by one of the Carnotaurs. Bruton returns to the herd and warns Kron that they are being followed, putting the entire herd in grave danger. Kron picks up the pace and quickly evacuates the herd, leaving Aladar, the lemurs, the older dinosaurs and Bruton behind, while the Carnotaurus are in pursuit some distance away. During a rainstorm, the stragglers spend the night in the cave, where Plio heals Bruton, and the Carnotaurs find and attack them. Bruton saves the others and sacrifices himself, causing a cave in to kill the female Carnotaurus in the process. As the rest of the group venture deeper through the cave, the male Carnotaurus having survived, resumes searching for the herd.
Aladar loses hope when they reach a dead end, but the others convince him to keep going, relating how he inspired them to do the same. After they knock down the dead end together and successfully find the Nesting Grounds on the other side. Eema sees a large wall of rocks blocking the original entryway to the valley. Knowing that the herd will die attempting to climb over it, Aladar rushes off alone to find them, and he gets pursued by the surviving Carnotaurus. As Aladar arrives to catch up with the herd and suggests the safer way to the valley, Kron furiously attacks him and they engage in battle until Neera stops them. The herd decides to abandon Kron and takes Aladar as their new leader. As they prepare to leave, the Carnotaurus confronts them. Aladar rallies the herd to stand together, and they bellow their way past the predator. The Carnotaurus pursues and injures Kron on the ledge of rocks. Aladar and Neera fight against the Carnotaurus until he falls off the cliff to his death. Kron dies from his injuries, with Aladar and Neera mourning for him.
The herd are led back to the Nesting Grounds as their new home. A new generation of dinosaurs hatches sometime later, along with Aladar and Neera's children. The lemurs find more of their kind, and soon they begin embarking on a new life together.
Directed by Ralph Zondag, Eric Leighton
Screenplay by John Harrison, Robert Nelson Jacobs
Story by John Harrison, Robert Nelson Jacobs, Thom Enriquez, Ralph Zondag
Starring D. B. Sweeney, Alfre Woodard, Ossie Davis, Max Casella, Hayden Panettiere, Samuel E. Wright, Julianna Margulies, Peter Siragusa, Joan Plowright, Della Reese,
Music by James Newton Howard
Cinematography David Hardberger, S. Douglas Smith
Edited by H. Lee Peterson
Release date May 19, 2000 (United States), October 13, 2000 (United Kingdom)
Running time 82 minutes
Country United States
Language English
Budget $127.5 million
Box office $349.8 million
