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Unlike other amniotes, synapsids have a single temporal fenestra, an opening low in the skull roof behind each eye socket, leaving a bony arch beneath each; this accounts for the name "synapsid". [7] The distinctive temporal fenestra developed about 318 million years ago during the Late Carboniferous period, [ 1 ] when synapsids and sauropsids ...
From top to bottom (A) a skull of an Anapsid, (B) a Synapsid (stem-mammal) skull, and (C) a Diapsid skull. [a] Temporal fenestrae are openings in the temporal region of the skull of some amniotes, behind the orbit (eye socket). These openings have historically been used to track the evolution and affinities of reptiles.
The modern view of synapsid relationships was proposed by paleontologist Robert R. Reisz in 1986, whose study included features mostly found in the skull rather than in the postcranial skeleton. [69] Dimetrodon is still considered a sphenacodont under this phylogeny , but varanodontids are now considered more basal synapsids, falling outside ...
The original synapsid skull structure has one hole behind each eye, in a fairly low position on the skull (lower right in this image). Synapsid skulls are identified by the distinctive pattern of the holes behind each eye, which served the following purposes: made the skull lighter without sacrificing strength. saved energy by using less bone.
Eothyris is a genus of extinct synapsid in the family Eothyrididae from the early Permian.It was a carnivorous insectivorous animal, closely related to Oedaleops.Only the skull of Eothyris, first described in 1937, is known.
The dicynodont skull is highly specialised, light but strong, with the synapsid temporal openings at the rear of the skull greatly enlarged to accommodate larger jaw muscles. The front of the skull and the lower jaw are generally narrow and, in all but a number of primitive forms, toothless.
These lists of synapsids collectively include every genus that has ever been included in the clade Synapsida- the mammals and their evolutionary precursors. The lists includes accepted genera along with those now considered invalid, doubtful (nomina dubia), not formally published (nomina nuda), junior synonyms of more established names, as well as genera that are no longer considered synapsids.
It has the longest skull of any early synapsid, reaching up to 50 centimetres (20 in) in one specimen. [3] The jaws are lined with many small teeth. It was larger than most other tetrapods (four-limbed vertebrates) of its time, ranging from 1.6 to 3 metres (5.2 to 9.8 ft) in length and 26 to 230 kilograms (57 to 507 lb) in weight.