See also: human Cranium, Cranium

The cranium is a seuse structure Os of the head characteristic of the Crâniate S (to which the vertebrate ones belong). This cranium protects the central Nervous system which is included there.

The temporal pits are anatomical features of cranium of the amniotes, characterized by bilateral symmetrical cavities in the temporal Os.

Physiological assumptions associate them with an increase in the metabolic levels and an increase in the musculature of the jaw. The first Amniote S of carboniferous did not have temporal pits whereas the Sauropside S and the more advanced Synapside S had some. During geological ages, the temporal pits of the sauropsides and synapsides changed and became broader to allow the establishment of muscles of the thicker jaws allowing more powerful bites. The Dinosaure S, which are sauropsides, have broad openings and their descendants the birds, have temporal pits which changed. The mammals, which are synapsides, do not have any more an opening on the level of cranium, so much the anatomical character was modified. They still however have the temporal Orbite (which resembles an opening) and the muscles temporal. It is about a hole in the head which is located at the back of the ocular orbit behind the eye.

The presence and the morphology of the temporal pits are a critical point for the taxonomic classification of the synapsides, to which the mammals belong.

The Euryapside S (plésiosauriens and of the ichtyosauriens) have only one large opening on the sides of their cranium, just like the synapsides, but the eurapsides are in fact of the Diapside S, from which the higher temporal pit disappeared.

The Anapside S (chéloniens) do not have any.

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