Here the temporal fossa is bridged over by the junction of the post-frontal and squamosal processes (pf., sq.).
In many owls the right and left ears are asymmetrical, and this asymmetry affects the whole of the temporal region, all the bones which surround the outer and middle ear, notably the squamosal and the quadrate, so that the skull becomes lopsided, one ear being turned obliquely down, the other upwards.
The quadrate is indirectly articulated with the skull, first by the horizontal, movable squamosal, secondly by the columella auris.
G, prefrontal; M, maxilla; J, poison-fang; Tr, transpalatine; Pt, pterygoid; p, palatine; Q, quadrate; Sq, squamosal; Pm, premaxilla; T.a, articular; Pe and Di, muscles.
Cope (Proc. Ac. Philad., 1864, p. 230) resorted to the modifications of the squamosal, ectoand endopterygoid bones, the condition of the vestigial limbs, and the teeth:- Scolecophidia (Typhlopidae), Catodonta (Glauconiidae), Tortricina (Ilysiidae and' Uropeltidae), Asinea, Proteroglypha and Solenoglypha.
No ectopterygoid pterygoid not extending to quadrate; no supratemporal or squamosal; prefrontal forming a suture with nasal; coronoid present; vestiges of pelvis present.
Squamosal large, suspending the quadrate: Boidae.
Squamosal small, intercalated in the cranial wall: Ilysiidae.
Squamosal absent: Uropeltidae.
Coronoid absent; squamosal present.
The quadrate is carried by the horizontally-elongated squamosal, which rests loosely upon the skull.
The quadrate is short and thick, and is carried by the broad and short squamosal, which lies flat against the skull, reminding in this respect of Ilysia.
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.
The under jaws are hinged on to the quadrate bones, which extend obliquely backwards, and are immovably wedged in between the squamosal and the lateral occipital wings.