In the timeframe of 10,000 BC, a tribe of hunter-gatherers called the Yagahl live in a remote mountain range in the Urals and survive by killing woolly mammoths, which they call "mannaks". The camp is led by a hunter who has proven his bravery by killing a Mammoth, and taking the White Spear. The people also strongly venerate an elderly woman, called Old Mother. Because of her different appearance to other humans in the village, it is assumed she is a Neanderthal, the "last of her kind", living with the Homo sapiens of the camp.
Des scientifiques parviennent à recréer des dinosaures et des ptérosaures. Mais lorsqu'ils présentent leurs résultats au public lors d'une conférence, les animaux s'échappent et sèment la panique dans les rues de Los Angeles, poursuivant particulièrement un pompier (Treat Williams) et sa fille (Jillian Rose Reed). Après avoir mangé beaucoup de monde, ils sont finalement tous tués.
Pendant trois cent mille ans, les Néandertaliens ont occupé l'Europe, mais leur espèce tend à disparaître : elle ne compte qu’un seul représentant, Ao. Son clan ayant été anéanti par des Homo sapiens, Ao commence à errer, sans cesse poursuivi par la vision de son frère Oa et décidé à revenir dans son vieux clan paternel. Il est capturé par une tribu d’Homo sapiens hostiles et fait la connaissance d’Aki, une femme Homo sapiens prisonnière. Tous les deux réussissent à s'échapper et avec le temps, après la méfiance et la suspicion que la femme avait initialement éprouvé envers cet homme différent, Ao et Aki commencent à se connaître et à se comprendre. À la fin Ao découvre qu'il est le dernier des Néandertaliens, mais il lui reste sa compagne, Aki, et les fruits de leur amour : sa petite fille et un nouvel enfant qui s’annonce.
George Loomis (William Katt) and and his wife Dr. Susan Matthews-Loomis (Sean Young) find a family of Mokele-mbembe (referred to as Brontosaurs) in Central Africa and they struggle to protect them from a greedy scientist named Dr. Eric Kiviat (Patrick McGoohan) and the military.
American scientist Steve Karnes (Gene Evans) delivers a speech to a British scientific society, headed by Professor James Bickford (André Morell), about the dangers to marine life posed by nuclear testing. Before Karnes can return to the U.S., a real-life example of his concern materializes when Tom Trevethan (Henri Vidon), an old fisherman, receives a lethal doze of radiation; his dying word is "behemoth". Later thousands of dead fish are washed ashore.
Set in the American Southwest, Doc (Raphael Sbarge) is an alcoholic security watchman protecting digging equipment from environmental activists, though he befriends one of them named Thrush (Jennifer Runyon). Meanwhile, Dr. Jane Tiptree (Diane Ladd) of the Eunice Corporation is breeding a strain of extra large and fertile chickens by splicing their DNA with that of crocodiles, iguanas, albatrosses, vultures, pelicans, turkeys and ostriches. Unknown to the Corporation's sponsors however, Tiptree is impregnating several of the chickens with dinosaur DNA. One of her resulting creatures, a Deinonychus, escapes and kills the activists, as well as other civilians. Doc investigates and discovers that Tiptree is also creating a virus which causes women to fatally conceive baby dinosaurs, in order to wipe out humanity and thus allow Carnosaurs and Raptors to reclaim the Earth as their own. Tiptree dies giving birth to a baby raptor. After narrowly escaping a Tyrannosaurus and the lab, Doc takes Thrush to a house to recover and injects a serum to cure her. Doc battles the Tyrannosaurus with a skidsteer (an action that was repeated in the fourth sequel) before impaling it. The government infiltrates the community in order to "sterilize" the situation by shooting all the civilians, infected or not. Thrush dies from the virus, meaning that the serum did not work. Doc is shot and killed by government soldiers, who then burn his and Thrush's bodies.
At the Yucca Mountain nuclear waste repository, repair crews are puzzled to find power cables ripped out from the ceiling. Meanwhile, a young hacker boy named Jesse is caught trying to steal dynamite. His uncle bails him out, and a workman teaches him how to operate a forklift, which contains a remote control to open the door to a deep elevator shaft. That night, an animal appears at the repository's mess hall and kills everyone but Jesse.
In the opening sequence, an army convoy is attacked by terrorists who soon discover they have stolen a truck of living frozen biological material instead of uranium. Once at a dockside warehouse, two frozen Velociraptors and a huge T-Rex escape and kill many of the terrorists before the police arrive, who expect to find drug smugglers. After finding the sole survivor, the police are killed inside the warehouse by the Velociraptors. An anti-terrorist special force led by Colonel Rance Higgins is called in by General Mercer where they find pieces of bodies and a refrigeration truck rather than uranium. They maneuver through warehouse boxes until two get slashed to death. The survivors learn from Dr. Hodges that these are the last three "carnosaurs" in existence: two male Velociraptors and one female T-Rex (the same dinosaurs in the convoy) left from the genetic reconstructions of the previous Carnosaur installments. It is made clear that the dinosaurs need to be caught alive, relating to the potential for curing major diseases. A massive meat shipment resides at the dock, so the three soldiers hunt in that area, meeting up with a unit of Marines who have come as backup. Soldier Polchek is given drugs to shoot into the carnosaurs as the group set up a lure and net trap with meat. One of the Velociraptors attacks and almost succeeds in dragging off Polchek, but is shot down. They soon take the raptor back to the base for further examination.
Dr. Abner Perry, a British Victorian period scientist (Cushing), and his US financier David Innes (McClure) make a test run of their Iron Mole drilling machine in a Welsh mountain, but end up in a strange underground labyrinth ruled by a species of giant telepathic flying reptiles, the Mahars, and full of prehistoric monsters and cavemen. They are captured by the Mahars, who keep primitive humans as their slaves through mind control. David falls for the beautiful slave girl Princess Dia (Munro) but when she is chosen as a sacrificial victim in the Mahar city, David and Perry must rally the surviving human slaves to rebel and not only save her but also win their freedom.
A North African dinosaur, related to the crocodile, is found which could grow up to fifty feet long. Dr. Campbell (Bruce Weitz) uses its DNA to create two hybrids of it with a modern-day crocodile at Paula Kennedy's Genetic Research Co. (Gereco) lab. One creature kills Dr. Campbell's assistant and the other creature before escaping. This information is kept from Sheriff Harper (Napier) by Kennedy, stating the dead creature killed Campbell's assistant. His daughter, county dog catcher Diane Harper, helps her ex welding artist, Tom Banning, and his 12-year-old brother Michael (Jake Thomas) find their three legged dog, Lucky, who was lost a few days earlier.
In 2004, not knowing how to run an abominable criminal recidivist while the death penalty has been abolished, FBI experts and lawyers condemned the imagine embarking on a journey through time To a time when the sentence still applied. For financial reasons, this expedition is coupled with a scientific mission on the planet Terra and charge of tracing the first dinosaurs. They do exist, and while the crew was launched in pursuit of the prisoner at large.
An army captain is flying three misfit deserters home for a court martial when the plane has engine trouble and they crash-land in the ocean near an uncharted island. There they find a primitive society of cave women who routinely sacrifice virgins to appease The Great One, the top dog dinosaur on the island. Mistaken for gods as part of a prophecy, the men must destroy The Great One or face death, but meanwhile they fall in love despite the advice of their Queen, who tries to disway them from being corrupted by the outsiders ways.
During the end of the Cretaceous era, an Iguanodon mother is forced to abandon her nest during a Carnotaurus attack. The one surviving egg journeys through several predicaments, before ending up on lemur island, where Plio names the hatched baby Aladar and raises him. Years later, Aladar and the lemurs take part in a mating season, where Zini goes without a mate. After the season ends, a meteor strikes and destroys the island, leaving Aladar, Plio, Yar, Zini and Suri, as the only survivors when they swim to the mainland. The family mourns for the loss of all lemurs before moving on.
After Yata (Toru Ibuki) is lost at sea, his brother Ryota (Toru Watanabe) steals a yacht with his two friends and a bank robber, the crew runs afoul of the giant lobster Ebirah, and washes up on the shore of an island, where a terrorist organization manufactures heavy water for their purposes, as well as a chemical that keeps Ebirah at bay. The organization, known as the Red Bamboo, has enslaved natives from Infant Island to help them, but the natives hope to awaken Mothra (now a full-grown moth metamorphosed from the larva that appeared in Ghidorah, the Three-Headed Monster) to rescue them.