300 - 240
240 - 180
180 - 120
120 - 60
60 - 0
300M
300 - 0
60M
2nd Galactic year
1st Galactic year of 250 million years 250 to present (not that present is the new year)
Phanerozoic Era 543 - Present
 
Tertiary 65 - 2.7
 
Paleozoic Era (Ancient Life)
Mesozoic Era (Middle Life) 248 - 65
Cenozoic Era 65 - Present
Carb
Permian Period
Triassic
Jurassic
Cretaceous Period 144 - 65
Pal
 

- 300 From amphibians came the first reptiles. Hylonomus is the earliest known reptile. It was 20 cm long (including the tail) and looked similar to modern lizards, had small sharp teeth and probably ate millipedes and early insects. It is a precursor of later amniotes and mammal-like reptiles.
- Evolution of the amniotic egg gives rise to the Amniota, reptiles who can reproduce on land and lay eggs on dry land. They did not need to return to water for reproduction. This adaptation gave them the capability to colonize the uplands for the first time.
Reptiles have advanced nervous system, compared to amphibians. They have twelve pairs of cranial nerves.

- 290 - 248 Permian Period
- 250 massive volcanic eruptions and devastating global warming. Only one in 10 species survived this cataclysmic end-Permian event.

- 248 - 206 Triassic Period
- 248 - 65 Mesozoic Era (Middle Life)
- 206 - 144 Jurassic Period
- 144 - 65 Cretaceous Period
- 65 - Present Cenozoic Era
- 65 - 55 Paleocene Epoch
- 65 - 2.7 Tertiary
- 2.7 - Present Quaternery