An experimental satellite-based weapon that fires miniature black holes, called the Dimension Tide, opens a wormhole through which a giant prehistoric dragonfly enters the present and deposits a single egg before exiting through the wormhole. A boy finds the egg and takes it with him when he moves to Tokyo. The egg starts oozing a strange liquid, so the boy throws the egg in the sewer. The egg, actually a mass of hundreds of eggs, splits up and starts growing when exposed to water, hatching into giant dragonfly larva called Meganulon that come out of the sewer to feed. They flood a portion of the city and moult on the sides of buildings, becoming adult Meganula.
When an ancient statue is moved for display in World Fair Expo 1970, a giant, vaguely Triceratops-like monster is released. The giant creature attacks and it’s up to Gamera to stop it.
The film concerns Starman’s efforts to save the Earth from the followers of Balazar, an evil genius from the planet Zemar whose brain has been preserved after his own assassination
Atomic Rulers of the World (or just Atomic Rulers) is a 1964 film edited together for American television from films #1 and #2 of the Japanese short film series Super Giant.