|541.0 ± 1.0 – 0 Ma|
|Regional usage||Global (ICS)|
|Time scale(s) used||ICS Time Scale|
|First proposed by||George Halcott Chadwick, 1930|
|Time span formality||Formal|
|Lower boundary definition||Appearance of the Ichnofossil Treptichnus pedum|
|Lower boundary GSSP||Fortune Head section, Newfoundland, Canada|
|Upper boundary definition||N/A|
|Upper boundary GSSP||N/A|
The Phanerozoic Eon is the current geologic eon in the geologic time scale, and the one during which abundant animal and plant life has existed. It covers 541 million years to the present, and it began with the Cambrian Period when animals first developed hard shells preserved in the fossil record. The time before the Phanerozoic, called the Precambrian, is now divided into the Hadean, Archaean and Proterozoic eons.
The time span of the Phanerozoic starts with the sudden appearance of fossilized evidence of a number of animal phyla; the evolution of those phyla into diverse forms; the emergence and development of complex plants; the evolution of fish; the emergence of insects and tetrapods; and the development of modern fauna. Plant life on land appeared in the early Phanerozoic eon. During this time span, tectonic forces which move the continents had collected them into a single landmass known as Pangaea (the most recent supercontinent), which then separated into the current continental landmasses.