"Mesozoic" (ちゅうせいだい Chūseidai) is an archetype used by Jim Crocodile Cook in the Yu-Gi-Oh! GX anime. Like the "Cenozoic" and "Paleozoic" archetype, the only support is "Time Stream". This archetype is related to the "Fossil", "Cenozoic" and "Paleozoic" archetype.

Mesozoic (meaning "middle life") is an interval of geological time from about 252 to 66 million years ago. It is one of three geologic eras of the Phanerozoic Eon, preceded by the Paleozoic ("ancient life") and succeeded by the Cenozoic ("new life").