Temporal fenestra
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The temporal fenestra is an amniote feature of the cranium. Physiological speculation associates it with a rise in metabolic rates and an increase in jaw musculature. The earlier amniotes of the Carboniferous did not have temporal fenestrae but the more advanced sauropsids and synapsids did. As time progressed, sauropsids' and synapsids' temporal fenestrae became more modified and larger to make stronger bites and more jaw muscles. Dinosaurs, which are sauropsids, have large advanced openings and their descendants, the birds, have temporal fenestrae which have been modified. Mammals, which are synapsids, possess no fenestral openings in the skull, as the trait has been modified. They do, though, still have the temporal orbit (which resembles an opening) and the temporal muscles. It is a hole in the head and is situated to the rear of the orbit behind the eye.
The presence and morphology of the temporal fenestra is critical for taxonomic classification of the synapsids, of which mammals are part.
Euryapsids have one large opening on the sides of their skulls, just like the synapsids, but eurapsids are actually diapsids, their upper temporal fenestra were lost.
Note:
- Synapsids - one opening
- Diapsids - two openings
- Anapsids - no openings
- Euryapsids - one opening (Eurapsids are part of diapsid group)
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