History of Mammals

History of Mammals
(mya = million years ago)
Long Geologic Time Chart
EON ERA PERIOD EPOCH PIVOTAL EVENTS
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“Visible Life”

Organisms with skeletons or hard shells.

540 mya through today.

P
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“Visible Life”

Organisms with skeletons or hard shells.

540 mya through today.

P
h
a
n
e
r
o
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c

E
o
n

“Visible Life”

Organisms with skeletons or hard shells.

540 mya through today.

P
h
a
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r
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c

E
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“Visible Life”

Organisms with skeletons or hard shells.

540 mya through today.

Cenozoic Era
“Age of Mammals”

65 mya through today

Quaternary Period
“The Age of Man”
1.8 mya to today
Holocene
10,000 ya to today
Human civilization
Pleistocene
1.8-.01 mya
The first humans (Homo sapiens) evolve. Mammoths, mastodons, saber-toothed cats, giant ground sloths, etc. A mass extinction of large mammals and birds 20,000 years ago, probably caused by ice ages.
Tertiary Period
65 to 1.8 mya
Neogene
24-1.8 mya
Pliocene
5-1.8 mya
First hominids (australopithecines). Modern forms of whales. Megalodon swam the seas
Miocene
24-5 mya
More mammals, including the horses, dogs and bears. Modern birds. South American monkeys, apes in southern Europe, Ramapithecus.
Paleogene
65-24 mya
Moeritherium
Oligocene
37-24 mya
Starts with a minor extinction (36 mya). Many new mammals (pigs, cats, rhinos, tapirs, Platybelodon appear). Grasses common.
Eocene
58-37 mya
Mammals abound. Rodents appear. Primitive whales appear.
Paleocene
65-58 mya
First large mammals and primitive primates, plesiadapiforms.
Mesozoic Era

“The Age of Reptiles”

245 to 65 mya

Cretaceous Period
146 to 65 mya

Upper
98-65 mya
High tectonic and volcanic activity. Primitive marsupials develop. Continents have a modern-day look. Minor extinction 82 mya. Ended with large extinction (the K-T extinction) of dinosaurs, pterosaurs, ammonites, about 50 percent of marine invertebrate species, etc., probably caused by asteroid impact or volcanism.
Lower
146-98 mya
The heyday of the dinosaurs. The first flowering plants, crocodilians, and feathered dinosaurs appear. Minor extinctions at 144 and 120 mya.
Jurassic Period
208 to 146 mya

Many dinosaurs, including the giant Sauropods. The first birds appear (Archaeopteryx). Many ferns, cycads, gingkos, rushes, conifers, ammonites, and pterosaurs. Minor extinctions at 190 and 160 mya.
Triassic Period
245 to 208 mya

The first mammals, dinosaurs, and crocodyloformes appear. Mollusks are the dominant invertebrate. Many reptiles. Triassic period ends with a minor extinction (35% of all animal families die out).
Paleozoic Era
540 to 245 mya

Paleozoic Era
540 to 245 mya

Permian Period
“The Age of Amphibians”
280 to 245 mya

“The Age of Amphibians” – Amphibians and reptiles dominant. Gymnosperms dominant plant life.The continents merge into a single super-continent, Pangaea. Phtyoplankton and plants oxygenate the Earth’s atmosphere to close to modern levels. The Permian ended with largest mass extinction. Trilobites go extinct, as do 50% of all animal families, 95% of all marine species, and many trees, perhaps caused by glaciation or volcanism.
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