The tympanic process of the alisphenoid bone of the skull is short, not covering the cavity of the tympanum, nor reaching the paroccipital process.
One of these, the processus orbitatis posterior, often combines with an outgrowth of the alisphenoid, and may be, e.g.
Dorsolaterally the basisphenoid is joined by the alisphenoid, which forms most of the posterior wall of the orbit.
An alisphenoid canal.
The post-glenoid, post-tympanic and paroccipital processes of the skull are large, and there is an alisphenoid canal.
No alisphenoid canal.
X P11,1x, premaxilla; Mx, maxilla; Ma, malar; Fr, frontal; L, lachrymal; Pa, parietal; Na, nasal; Sq, squamosal; Ty, tympanic; ExO, exoccipital; AS, alisphenoid; OS, orbito-sphenoid; Per, mastoid bulla.
An alisphenoid canal may be present on the palatal aspect of the skull; but there is always a transverse canal.
In the skull the infra-orbital foramen is narrow, and postorbital processes and an alisphenoid canal are absent.
The incisive foramina are large and usually confluent; the bony palate is very narrow from before backwards; there is no alisphenoid canal; the fibula is welded to the tibia, and articulates with the calcaneum; and the testes are permanently external.
The pterygoids are delicate slender slips of bone attached to the hinder border of the palatines, and supported externally by, and generally welded with, the rough pterygoid plates of the alisphenoid, with no pterygoid fossa between.
There is a distinct alisphenoid canal for the passage of the internal maxillary artery.
The base of the cranium is long and narrow; the alisphenoid is very obliquely perforated by the foramen rotundum, but the foramen ovale is confluent with the large foramen lacerum medium behind.