Labelling the Fenestrae in a Diapsid Skull

Recently, Everything Dinosaur posted up a picture of the skull of a large gharial and discussed the teeth located in distinct sockets, an anatomical trait characteristic of that great group of reptiles the Archosaurs (Archosauria).  Today, we complete this very brief look at the Archosaurs by labelling the fenestrae (holes) in the skull that identify the gharial, all crocodiles and their close relatives, including the dinosaurs, that are classified as diapsid reptiles.

The Skull of the Gharial with the Eye Socket (Orbit) and Fenestrae Labelled

A gharial skull with the fenestrae and eye sockets labelled.

Labelling the skull of a diapsid reptile.

Picture Credit: Everything Dinosaur

The gharial (a long-snouted, crocodilian), skull is from the Grant Museum of Zoology and Comparative Anatomy (London).  In the photograph (above), we have labelled the holes (fenestrae) in the skull, the left lateral side of the skull is seen and the lower (inferior) temporal fenestra has been labelled.  Behind the large orbits (eye sockets), on the top of the skull, the pair of upper (superior) temporal fenestrae have been labelled.  Please note each of the holes (singular) is termed a fenestra, but the plural is fenestrae.

The diapsid reptiles are an extremely diverse group that contains a number of extinct kinds of reptile as well as snakes, lizards, turtles, the last surviving member of the ancient order Ryhnchocephalia – the tuatara, crocodiles, dinosaurs and birds.  The last three listed, crocodiles, dinosaurs and birds are of course Archosaurs, and the Archosauria are characterised by a number of anatomical features including the two pairs of skull fenestrae.

The holes in the skull probably evolved to permit larger muscle attachments for the jaws, giving these animals a stronger bite.  The mouth could also be opened wider, a definite advantage of you are having to bolt down lumps of flesh or to cram into your stomach large amounts of nutritionally poor vegetation.

To read our article about another feature of the Archosauria – tooth sockets: A Feature of the Archosauria (Part 1)

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