Question

What are the three eras within the Phanerozoic eon?

Answer 1

The three eras within the Phanerozoic eon are

• the Paleozoic era (541 million to 252 million years ago)
• the Mesozoic era (252 million to 66 million years ago)
• the Cenozoic era (66 million years ago to the present)

Explanation:

The Phanerozoic eon is the eon of abundant complex life.
It is the eon we are living in.

`color(white)(.................)` ———————————

`"Before the Phanerozoic Eon"`

During the long long time before our eon, there was little or no life.
That span of time is called the Precambrian. The Precambrian makes up almost 90% of the earth's history `-` everything between the formation of the earth 4.6 billion years ago up to 600 million years ago.

The Precambrian eons before the proliferation of complex life (our Phanerozoic eon) are:

• the Hadean Eon
• the Archean eon
• the Proterozoic Eon
  https://www.livescience.com/43354-precambrian-time.html

`color(white)(.................)` ———————————

`"The Phanoerozoic Eon"`

At long last, complex life sprang into being, with the
`color(white)(.................)`Cambrian Explosion.

http://www.bbc.co.uk/nature/history_of_the_earth/Cambrian

The Cambrian Explosion is the beginning of the Phanerozoic eon, divided into three eras.

• The Paleozoic Era
  ▸ The Paleozoic Era is the oldest of the three Eras and dates from 540 Million to 248 Million Years Ago.
  ▸ During the Paleozoic Era, multicelled living things acquired hard body parts, bones, vertebral columns, mandibles, and teeth.
  ▸ Common in the Paleozoic Era were trilobites, crinoids, brachiopods, fish, insects, amphibians, and early reptiles.

• The Mesozoic Era
  ▸ The Mesozoic Era extended from 248 Million to 65 Million Years Ago.
  ▸ The Mesozoic Era was important for the fossil remains of the dinosaurs and other reptiles that lived.
  ▸ However, the Mesozoic Era landscape was also occupied by insects, early mammals, plants such as conifers and ferns, fish, and finally flowering plants and early birds.

• The Cenozoic Era
  ▸ The Cenozoic Era began 65 Million Years Ago with the extinction of the dinosaurs and continues into the Present.
  ▸ The extinction of the dinosaurs at the end of the Mesozoic Era opened up vast new habitats and environments for early mammals and birds to adapt to and occupy.
  http://imnh.isu.edu/exhibits/online/geo_time/geo_time_eras.htm

Here's a geological time scale of the three eras of the Phanerozoic

https://andyckh.deviantart.com/art/Geological-Timeline-Chart-283922560