GEOLOGIC TIMELINE
PALEOZOIC ERA
CAMBRIAN PERIOD (570 million years ago to 505 million years ago)
ORDOVICIAN PERIOD (505 million years ago to 438 million years ago)
438 Taconic Orogeny (first of three mountain building episodes in North America
SILURIAN PERIOD (438 million years ago to 408 million years ago)
~425 First land plants
420 Fish developed teeth and jaws
DEVONIAN PERIOD (408 million years ago to 360 million years ago)
375 First amphibians
360 Acadian Orogeny (second micro-continent impact causes new mountain range)
MISSISSIPPIAN PERIOD (360 million years ago to 320 million years ago)
PENNSYLVANIAN PERIOD (320 million years ago to 280 million years ago)
Extensive "coal swamps"
~310 First reptiles
240 Alleghenian Orogeny (African plate impacts North America, causing Allegheny Mountains)
PERMIAN PERIOD (280 million years ago to 225 million years ago)
MESOZOIC ERA
TRIASSIC PERIOD (225 million years ago to 190 million years ago)
The first turtles, crocodiles, dinosaurs, sea reptiles, flying reptiles, and mammals appear.
~225 First modern bony fish
~210 Pangea breaks up
JURASSIC PERIOD (190 million years ago to 135 million years ago)
The first birds appear. Dinosaurs reach their greatest size. Insects were plentiful. Ammonites flourish in the sea. Mammals begin.
~190 First birds
CRETACEOUS PERIOD (135 million years ago to 65 million years ago)
Horned and armored dinosaurs become common. Flowering plants develop. Mammals expand.
130 Monotremes diverge from mammal lineage
120 Marsupials and Placentals diverge in mammal lineage
CENOZOIC ERA
TERTIARY PERIOD (65 million years ago to 3 million years ago)
65 PALEOCENE EPOCH (Mammals expand rapidly)
60 First rodents and lagomorphs
53 EOCENE EPOCH (First camels, horses, and other mammals appear)
36 OLIGOCENE EPOCH (Grasslands spread, primitive apes appear)
30 MIOCENE EPOCH (Mammals reach their greatest diversity)
8 PLIOCENE EPOCH (Human beings appeared)
QUATERNARY PERIOD (3 million years ago to present)
2 PLEISTOCENE EPOCH (Modern human beings develop. Ice Age begins)