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Temporal fenestrae in relation to the other skull openings in the dinosaur Massospondylus, a type of diapsid. The supratemporal fenestra, also called the upper temporal fenestra, is positioned above the other fenestra and is exposed primarily in dorsal (top) view. In some reptiles, particularly dinosaurs, the parts of the skull roof lying ...
A euryapsid skull. Euryapsida is a polyphyletic (unnatural, as the various members are not closely related) group of sauropsids that are distinguished by a single temporal fenestra, an opening behind the orbit, under which the post-orbital and squamosal bones articulate.
An anapsid is an amniote whose skull lacks one or more skull openings (fenestra, or fossae) near the temples. [1] Traditionally, the Anapsida are considered the most primitive subclass of amniotes, the ancestral stock from which Synapsida and Diapsida evolved, making anapsids paraphyletic. It is, however, doubtful that all anapsids lack ...
The name Diapsida means "two arches", and diapsids are traditionally classified based on their two ancestral skull openings (temporal fenestrae) posteriorly above and below the eye. This arrangement allows for the attachment of larger, stronger jaw muscles , and enables the jaw to open more widely.
This schematic shows the skull viewed from the left side. The middle opening is the orbit of the eye; the opening to the right of it is the temporal fenestra. Synapsids evolved a temporal fenestra behind each eye orbit on the lateral surface of the skull. It may have provided new attachment sites for jaw muscles. A similar development took ...
The squamosal and the jugal bone, by touching each other, excluded the quadratojugal from the edge of the lateral temporal fenestra, i.e. the opening at the rear of the skull side. [49] The frill of Achelousaurus had two conspicuous large spikes that were directed backwards and curved to the sides away from each other. During the 1990s, it was ...
However, because more primitive rhynchocephalians have an open lower temporal fenestra with an incomplete temporal bar, this is thought to be derived characteristic of the tuatara and other members of the clade Sphenodontinae, rather than a primitive trait retained from early diapsids. The complete bar is thought to stabilise the skull during ...
The upper edge of the temporal fenestra is formed by the parietal bone, which differs in structure between Rautiania species. In R. alexandri, the parietal possesses a row of thin, blocky structures which conjoin at their base. R. minichi, on the other hand, has a row of large, widely spaced spines on its parietal.