Earl Sinclair must choose his role in life: That of domesticated dinosaur or wilderness dinosaur. After 24 years with the Wesayso Development Corporation, Earl asks for a raise -- and instead is terminated by his angry boss, B.P. Richfield. Highly distressed, Earl returns home to discover that his wife, Fran, has laid an egg.

When Fran feels like a dowdy, neglected housewife after hatching her third child, husband Earl realizes -- to his horror -- that he's going to have to relearn the mating dance to woo Fran back to feeling attractive and wanted again.

When dinosaurs turn 72 years old, they're thrown over the cliff into the tar pit so they won't be a burden to their families. Earl's mother-in-law, Ethyl, is quickly approaching her 72nd birthday, and Earl can hardly wait. But when son Robbie suggests that Grandma Ethyl move in with them instead, Earl may become the first dinosaur to give up his den in the name of family unity.

When a gigantic dinosaur, nine times Earl's size, falls for Fran at the grocery store, he decides he wants her -- and everything else Earl loves -- for his own. Earl has to decide whether to summon up his courage and fight for his family or follow the dinosaur's code of the wilderness and run like crazy.

Earl's son, Robbie, rebels against the dinosaur tradition of howling as the rite-of-passage to adulthood, but gets caught in the middle when his act of rebellion sets best friends Earl and Roy at each other's throats.

The Sinclairs are concerned when Baby grows a golden horn on his head, but their concern turns to astonishment when the Council of Elders announces that Baby's horn makes him the long-awaited king of the dinosaurs!