An infratemporal fenestra, also called the lateral temporal fenestra is an opening in the skull behind the orbit

Orbit (anatomy)

In anatomy, the orbit is the cavity or socket of the skull in which the eye and its appendages are situated. "Orbit" can refer to the bony socket, or it can also be used to imply the contents...

 in some animals. An opening in front of the eye sockets, conversely, is called an antorbital fenestra

Antorbital fenestra

An antorbital fenestra is an opening in the skull, in front of the eye sockets. This skull formation first appeared in archosaurs during the Triassic Period. Living birds today possess antorbital fenestrae, but the feature has been lost in modern crocodilians...

. Both of these openings reduced the weight of the skull. Infratemporal fenestrae are commonly (although not universally) seen in the fossilized skulls of dinosaur

Dinosaur

Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...

s.