|Eon||Era||Period||Epoch||Start Million years ago|
The other two periods of time that make up the Triassic are usually called the Lower and Middle Triassic.
Many early dinosaur species appeared for the first time during the Upper Triassic, including Plateosaurus, Coelophysis, and Eoraptor. Pterosaurs were common in the air, and Ichthyosaurs dominated the seas.
At the end of the Upper Triassic some catastrophic event or events caused the extinction of many animal species worldwide. Known as the end–Triassic extinction event, it was similar to the more famous event that lead to the extinction of the dinosaurs, except no one knows for sure what caused the event.
- International Chronostratigraphic Chart. 
- Triassic: from Latin meaning "triple" or "group of three"
|Precambrian (4.567 gya – 541 mya)|
|In the left column are Eons, bold are Eras, not bold are Periods. gya = billion years ago, mya = million years ago|
|Hadean (4.567 gya – 4 gya)|
|Archaean (4 gya – 2.5 gya)|
|Proterozoic (4 gya – 2.5 gya)||Palaeoproterozoic (2.5 gya – 1.6 gya)|
|Phanerozoic (541 mya – today)|
|In the left column are Eras, bold are Periods, not bold or italics are Epochs, Italics are stages. kya = thousand years ago, mya = million years ago|
|Palaeozoic (541 mya – 252.17 mya)||Cambrian (541 mya – 485.4 mya)|
|Mesozoic (252.17 mya – 66.0 mya)||Triassic (252.17 mya – 201.3 mya) Lower Triassic (252.17 mya – 247.2 mya) Middle Triassic (247.2 mya – 237 mya) Upper Triassic (237 mya – 201.3 mya)|
|Cainozoic (66.0 mya – today)||Palaeogene (66.0 mya – 23.03 mya) Palaeocene (66.0 mya – 56 mya) Eocene (56 mya - 33.9 mya) Oligocene (33.9 mya – 23.03 mya)|
|Source||International Chronostratigraphic Chart 2013. International Commission on Stratigraphy, retrieved 8 April 2013. Divisions of geologic time – major chronostratigraphic and geochronologic units USGS, retrieved 8 April 2013.|