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ZoomDinosaurs.com
Dinosaur and Paleontology Dictionary
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

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GEOLOGIC EONS, ERAS and PERIODS

The period is the basic unit of geological time in which a single type of rock system is formed. Two or more periods comprise a geological Era. Two or more Eras form an Eon, the largest division of geologic time. Some periods are divided into epochs.

The major periods in the geologic history of the Earth are (mya=million years ago):

EON ERA PERIOD
P
H
A
N
E
R
O
Z
O
I
C


540 mya through today
CENOZOIC Quarternary 1.8 mya-today
First humans, mammoths, mastodons, saber-toothed cats.
Neogene 24-1.8 mya
Australopithecus appears. First sheep, cattle, modern whales, bears, mice, rats, apes, monkeys, dogs, modern birds appear.
Paleogene 65-24 mya
First deer, cats, pigs, tapirs, and rhinos, elephants, horses, owls, shrews, hedgehogs, and rabbits evolve.
MESOZOIC Cretaceous 146 to 65 mya
First flowering plants, snakes, crocodilians. K-T mass extinction at end kills dinosaurs, and others
Jurassic 208 to 146 mya
Abundant dinosaurs, first birds.
Triassic 245 to 208 mya
First mammals, dinosaurs, frogs, turtles, crocodyloformes.
PALEOZOIC Permian 280 to 245 mya
Sail-back reptiles. Amphibians abundant. Pangaea forms. Ends with mass extinction.
Carboniferous 360 to 280 mya
Widespread coal swamps. First reptiles, winged insects.
Devonian 408 to 360 mya
First amphibians, sharks, bony fish, ammonoids, and spiders. Many fish.
Silurian 438 to 408 mya
First insects, vascular plants on land.
Ordovician 505 to 438 mya
First land plants, corals, Nautiloids. Ends in mass extinction.
Cambrian 540 to 500 mya
Explosion of life forms. First shellfish, primitive fish, trilobites, corals, mollusks.
PROTERO-
ZOIC

2.5 billion years ago to 540 mya
- Vendian 600 to 540 mya
Sponges, multi-celled animals appear. Supercontinent Rodinia.
- Early Proterozoic 2.5 billion years to 600 mya
Oxygen build-up on Earth. First multi-cellular life.
ARCHEO-
ZOIC

3.9 to 2.5 billion years ago
- -
HADEAN
4.6 to 3.9 billion years ago
- -



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