Based on skull morphology, amniotes can be divided:
1. Anapsids-It is a group of organisms with skulls that lack openings called temporal fenestrae.Turtles are an example of Anapsids.
2. Diapsids-It is a group of organisms with skulls that have two temporal fenestrae behind the orbit, one superior and one inferior. Examples are crocodilians, birds, tuataras, lizards and snakes.
3. Synapsids-It is a group of organisms that have one temporal fenestra behind the eye. The example is mammals.
