ERA	PERIOD	MILLION YEARS AGO	EVENTS
C E N O Z O I C	holocene pleistocene pliocene miocene oligocene eocene paleocene	.01 1.8 24 65	evolution of men ice age; phosphate forms lots of mammals on earth
M E S O Z O I C	cretaceous jurassic triassic	141 195 230	last dinosaurs; first flowers and primates lots of dinosaurs; first birds First dinosours and mammals
P A L E O Z O I C	permian pennsylvanian mississipian devonian silurian ordovician cambrian	280 320 345 395 435 500 570	many ocean animals were extinct first reptiles trees and ferns appeared fishes with jaws and amphibians land plants appear lots of soft bodied animals first fish and chordate animals
P R E C A M B R I A N	precambrian	4,500	first animals with skeletons such as clams and trilobites first soft body animals like jellyfish or sponge one-celled organisms