Kaiju (Pacific Rim)

In Pacific Rim series, Kaiju refers to Precursors' series of titanic, drift-controlled monsters from Anteverse.

Triassic Period
First Kaijus were developed by Precursors sometime prior or during Triassic Period, yet at that time Earth's environment was too hostile for either them or Kaijus to enter, resulting them halting their terraforming plan.