First amniotes
c. 320 million years ago · Event
Small lizard-like animals in the Carboniferous forests evolve an egg with a shell and its own private pond inside — and vertebrates are finally free of the water. Almost immediately the amniote family splits in two: the sauropsid line, leading to reptiles, dinosaurs and birds, and the synapsid line, leading through Dimetrodon and the therapsids to mammals. Every entry after this one sits on one side or the other of that fork.
On these timelines: Master, The Age of Dinosaurs
Around 320000000 BCE
- Permian Period (299000000 BCE)
- Dimetrodon (295000000 BCE)
- Carboniferous coal forests (310000000 BCE)