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The squamosal is a skull bone found in most reptiles, amphibians, and birds. In fishes, it is also called the pterotic bone. [1] In most tetrapods, the squamosal and quadratojugal bones form the cheek series of the skull. [2] The bone forms an ancestral component of the dermal roof and is typically thin compared to other skull bones. [3]
The internal surface of the squamous part is concave and presents in the upper part of the middle line a vertical groove, the sagittal sulcus, the edges of which unite below to form a ridge, the frontal crest; the sulcus lodges the superior sagittal sinus, while its margins and the crest afford attachment to the falx cerebri.
The squamosal suture, or squamous suture, arches backward from the pterion and connects the temporal squama with the lower border of the parietal bone: this suture is continuous behind with the short, nearly horizontal parietomastoid suture, which unites the mastoid process of the temporal with the region of the mastoid angle of the parietal bone.
Turtles have an anapsid skull, but this was likely acquired secondarily from a diapsid ancestor. Synapsida – One low opening (beneath the postorbital and squamosal bones). A monophyletic group including mammals and their ancestors. Euryapsida – One high opening (above the postorbital and
10 – squamosal, 11 – occipital, 12 – mandible. Date: 7 August 2013, 06:44:00: Source: Own work,based on: ... Lateral view of skull of a Dog: Licensing. I, the ...
Diagram showing the skull from above and the left side. The epiossifications on the squamosal bones of Kosmoceratops became progressively larger towards the back of the neck frill. There were five well-developed epiossifications per side on the hind-margin of the frill: three forward-curved epiparietals (ep 1–3) on the parietal bone, one ...
The mammalian jaw joint is composed of different skull bones, including the dentary (the lower jaw bone which carries the teeth) and the squamosal (another small skull bone). In mammals, the quadrate and articular bones have evolved into the incus and malleus bones in the middle ear. [20] [21]
Bony parts include the skull, the axial skeleton (spine and ribs), and the appendicular skeleton (girdles and limbs). [21] Most of these bones are paired , with a mirror-inverted counterpart on the other side of the body, or unpaired , in which case they usually lie at the body midline and are divided by the latter into two symmetrical halves ...