Antorbital fenestra

The Antorbitalfenster (English antorbital fenestra ) is a cranial window in terrestrial vertebrates from the group Archosauria. It is located on the side of the skull between the eye socket (orbit ) and the nasal opening (external naris ). It is found in modern birds, is in today's crocodiles but closed. The Antorbitalfenster located within a cranial fossa ( fossa ), the Antorbitalen fossa. It houses the antorbitalen sinuses. The name Antorbitalfenster consists of the words anterior - together and orbit ( " Orbital " ) and points to the location of the window in front of the eye sockets (from Latin ante "before" ).

Long regarded as the Antorbitalfenster common derived character ( synapomorphy ) of the Archosauria, was therefore used for the delineation of this group. Today, the Antorbitalfenster is considered a synapomorphy somewhat broader group of Archosauriformes. The Antorbitalfenster has in the evolution of Archosauria at least 10 times independently closed - so when different groups of crocodile relatives ( Crocodylomorpha ), with most groups of birds Beck dinosaur ( Ornithischia ) as well as in some birds, such as some owls.

In lizards Beck dinosaurs ( Saurischia ) this skull window is often very large and sometimes larger than the eye socket. In advanced theropods ( carnivorous dinosaurs ) are often found additional, smaller cranial window, which lie immediately before the Antorbitalfenster within the Antorbitalen fossa - the Maxillarfenster and the Promaxillarfenster.