page_title: Skull
section_title: Fenestrae
hierarchical_section_title: Skull / Structure / Other vertebrates / Fenestrae
caption_attribution_description: A skull diagram of the prosauropod dinosaur Massospondylus; showing the various holes in the skull (fenestra). • Based on [1] and images in 'The Dinosauria Second Edition' 2004. NOTE: I often update my images. If you want to have any of my images on a website, please (if possible) don’t host/save it to the website server. I’d prefer it if the image's Wikimedia URL is used. This means that if I update an image, it will be updated on the site as well. Thanks.
context_page_description: The skull is a bony structure that forms the head in vertebrates. It supports the structures of the face and provides a protective cavity for the brain. The skull is composed of two parts: the cranium and the mandible. In humans, these two parts are the neurocranium and the viscerocranium that includes the mandible as its largest bone. The skull forms the anterior-most portion of the skeleton and is a product of cephalisation—housing the brain, and several sensory structures such as the eyes, ears, nose, and mouth. In humans these sensory structures are part of the facial skeleton.
  Functions of the skull include protection of the brain, fixing the distance between the eyes to allow stereoscopic vision, and fixing the position of the ears to enable sound localisation of the direction and distance of sounds. In some animals, such as horned ungulates, the skull also has a defensive function by providing the mount for the horns.
  The English word "skull" is probably derived from Old Norse "skulle", while the Latin word cranium comes from the Greek root κρανίον.
context_section_description: The fenestrae (from Latin, meaning windows) are openings in the skull.
  Antorbital fenestra
  Mandibular fenestra
  Quadratojugal fenestra
  Subsquamosal fenestra, an opening between two parts of the squamosal bone in some rodents
  Temporal fenestra
  The temporal fenestrae are anatomical features of the skulls of several types of amniotes, characterised by bilaterally symmetrical holes (fenestrae) in the temporal bone. Depending on the lineage of a given animal, two, one, or no pairs of temporal fenestrae may be present, above or below the postorbital and squamosal bones. The upper temporal fenestrae are also known as the supratemporal fenestrae, and the lower temporal fenestrae are also known as the infratemporal fenestrae. The presence and morphology of the temporal fenestra are critical for taxonomic classification of the synapsids, of which mammals are part.
  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 two more advanced lines did: the synapsids (mammal-like reptiles) and the diapsids (most reptiles and later birds). As time progressed, diapsids' and synapsids' temporal fenestrae became more modified and larger to make stronger bites and more jaw muscles. Dinosaurs, which are diapsids, have large advanced openings, and their descendants, the birds, have temporal fenestrae which have been modified. Mammals, which are synapsids, possess one fenestral opening in the skull, situated to the rear of the orbit.
caption: The fenestrae in the skull of the dinosaur Massospondylus
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