The phanerozoic eon is made up of all of the following except the era.

The Phanerozoic eons is made up of the following except the Permezoic Era. Eons are the largest interval units into which Geologic time is divided and represented. Phanerozoic is among the four geologic Eons; other three are; the Hadean, Archean, and Proterozoic Eons. The Phanerozoic Eon began 540 Million years ago and continues into the Present. It consists of three eras namely; Paleozoic era, Mesozoic era and Cenozoic era.