The Ordovician Organisms (South Park)

The Cretaceous Organisms is an upcoming South Park episode which features the mesozoic ancestors of the modern day characters.

Premise
Sixty million years before the events of Cartman Gets an Anal Probe, the single-celled organism/amoeba mesozoic ancestors of Cartman, Stan, Kyle, and Kenny are living beneath the Pacific Ocean during the Cretaceous era. In the beginning of the episode, they hatch from eggs at the very bottom of the Mariana Trench, but as the episode progresses they attempt to make their way to the Great Barrier Reef, but as they begin their odyssey they encounter many marine beings that threaten their lives such as giant squids, angler fishes, pacific viperfishes, giant spider crabs, six-gilled sharks, stingrays, etc. Despite never meeting anyone else but themselves, the four organisms were biologically wired to seek out their friends and family, and they eventually make to the reef and unite with them. In the last five minutes of episode, the four main characters begin to follow a amphibian creature in the ocean, and it had just evolved from a form of fish. The amphibian then made its way to the surface, with the four main characters clutching onto its tail, with all the organisms following their lead. The organisms then evolved into humanoids that strongly resemble their modern descendants, and then crawled onto land with the amphibian leading the way, until it is crushed by a Tyrannosaurus.

Trivia

 * The 2D hand-drawn animated sequences while the characters were underwater utilized in cel animation that was handled overseas in South Korea at Rough Draft Studios.
 * The animation also bears a striking resemblance to the cartoon segment in the opening scene of the "Minions" movie.
 * When the characters emerge out of the sea, they communicate solely with grunts and growls. This is due to humans not developing a language system until about two millions years ago.