The four main time scales, starting from the earliest, are:
Precambrian- This era consisted of single-celled organisms and multicellular organisms also began to arise in this time period.
Paleozoic- The early part of this era primarily had fish and the latter part of the era consisted of amphibians and reptiles.
Mesozoic- The mesozoic era had dinosaurs, birds and some flowering plants
Cenozoic- Many dinosaur species had gone extinct and this era contains mammals.
