Antorbital fenestra

Opening in the skull in front of the eye sockets, largely associated with archosauriforms

An antorbital fenestra is an opening in the skull that is in front of the eye sockets. This skull character is largely associated with archosauriforms, first appearing during the Triassic Period. Among extant archosaurs, birds still possess antorbital fenestrae, whereas crocodylians have lost them. The loss in crocodylians is believed to be related to the structural needs of their skulls for the bite force and feeding behaviours that they employ. In some archosaur species, the opening has closed but its location is still marked by a depression, or fossa, on the surface of the skull called the antorbital fossa.

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