Dinosaur egg clutch

Amniotes appeared more than 310 million years ago and layed their eggs out of the water. Their skin was covered with scales, hair, or feathers so protecting them from dehydration. Once out of their aquatic setting, they subsequently colonised dry land. The continents were rapidly populated by amniotes. Even though the earliest of them may seem very different to us from those of today, all the current large groups of amniotes existed, including those to which we belong: the synapsids.

The enormous evolutionary success of the amniotes is largely due to the amniotic egg: it meant they no longer had to lay their eggs in water.