The Permian Period, at the end of the
Paleozoic era, marked a great changes in the Earth's climate and appearance.
Trilobites and other marine groups became extinct, and a group of small reptiles (diapsids) abound. These were the ancestors to most modern reptiles and the ruling dinosaurs as well as pterosaurs and crocodiles. Thriving also, were the early ancestors to mammals (synapdia), which included some large reptiles such as
dimetrodon. Reptiles grew to dominance among
vertebrates, because their special adaptations
enabled them to flourish in the drier climate. The warm zone
spread in the northern hemisphere, where extensive dry desert
appeared. The rock formed at that time were stained red by
iron oxides, the result of intense heating by the sun of a surface
devoid of vegetation cover. the old types of plants and
animals died out.