Known as Age of the Reptiles.
this might help out
Toward the beginning of the Mesozoic Era there was a depleted ecosystem world-wide. Many of the old life forms had just gone extinct in the Permian Extinction, the world's largest mass extinction. This depleted state was followed by an explosion of new life forms, which included the dinosaurs and mammals, and later in the Mesozoic, the birds and flowering plants.
