Skull window
The skull windows are larger recesses in the bony skull of vertebrates, through which the masticatory muscles could be shifted from the inside to the outside of the skull in the course of evolution . As a result, stronger muscle strands and thus stronger teeth could develop due to the larger attachment surface for the muscles . Furthermore, the space gained inside the skull increased the brain volume .
In the Synapsida (which includes mammals as well as some extinct taxa ) there is a skull window behind the eye socket in the temple area (synapsid skull). A secondary closure of the temples then resulted in a new brain skull in the mammals; the original temple window is formed as a zygomatic arch in them .
The Diapsida (includes all birds and reptiles except for the turtles) formed two skull windows behind the eye sockets (diapsid skull). This basic shape of the skull has been partially dissolved and has developed into a skull that is only very clasp-like in birds and snakes, for example.
The skull of the turtle is called anapsid skull . Normally this has no windowing. However, “cranial windows” can also arise here, for example due to the formation of the salt glands in sea turtles (interorbital foramen between the eyes).
Generalized anapsid skull
Generalized synapsid skull
Generalized diapsid skull
