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 first synapsids appeared over 300 million years ago and rapidly became the most diversified of the amniotes. In the Mesozoic Era, only two branches remained: the dicynodonts and the cynodonts. Mammals emerged from the latter and they are now the last representatives of the synapsids. At the beginning of the Mesozoic era, a group of sauropsids became more important and outgrew the synapsids: these were the archosaurs. They rapidly split into two branches. One gave rise to the crocodile and one to the pterosaurs and all the dinosaurs, including birds.
Camarasaurs first appeared 155 million years ago in North America and disappeared around 144 million years ago. They were part of the group of sauropods, the largest herbivores to have walked the earth. This specimen measures 14 metres in length and 4.5 metres in height at the shoulder.