antorbital

Antorbital is an anatomical term used to describe structures located in front of the orbit (eye socket) or relating to the antorbital region of the skull. The word derives from Latin ante- “before” and orbital.

In the context of archosaurs, the antorbital fenestra is a prominent opening in the skull positioned anterior to the eye. This fenestra is commonly associated with pneumatic (air-filled) spaces and contributes to a lighter skull. The surrounding bones and the extent of the opening vary among species, and in some lineages the fenestra becomes reduced or is partially obscured by bone.

The antorbital region and fenestra are of particular interest in paleontology because they are characteristic features of Archosauria, a group that includes crocodilians, dinosaurs (including birds), and their extinct relatives. The presence, absence, or modification of the antorbital fenestra helps scientists diagnose fossil skulls, infer relationships, and study the evolution of skull pneumatization linked to respiratory systems.

In modern birds, evolutionary changes have altered the original antorbital anatomy seen in many non-avian archosaurs; in some lineages the fenestra is reduced or less conspicuous, while in others it remains more evident in the skull morphology. The term antorbital can also describe other features near the orbit that are situated toward the front of the skull, though its most widely recognized use is in reference to the antorbital fenestra.