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.
Premolars compressed, pointed; and the molars with quadrate tuberculated crowns.
To the left of the gall bladder is the quadrate lobe, which is in contact with the pylorus of the stomach.
A diagnosis covering all the Ratitae (struthio, rhea, casuarius, dromaeus, apteryx and the allied fossils dinornis and aepyornis) would be as follows - (i) terrestrial birds without keel to the sternum, absolutely flightless; (ii) quadrate bone with a single proximal articulating knob; (iii) coracoid and scapula fused together and forming an open angle; (iv) normally without a pygostyle; (v) with an incisura ischiadica; (vi) rhamphotheca compound; (vii) without apteria or bare spaces in the plumage; (viii) with a complete copulatory organ, moved by skeletal muscles.
In tracing the lobulation of man's liver back to this generalized type, it is evident at once that his quadrate lobe does not correspond to any one generalized lobe, but is merely that part of the right central which lies between the gall bladder and the umbilical fissure.
The maxillaries are connected with the distal anterior corner of the quadrate by the thin, splint-like jugal and quadratojugal.
The last premolar and the molars have quadrate crowns, provided with two strong transverse ridges, or with four obtuse cusps.
Molars with quadrate crowns and a blunt conical cusp at each corner, the last notably smaller than the rest, sometimes rudimentary or absent.
Of scaly reptiles with movable quadrate bones; with a transverse vent, near the posterior lateral corners of which open the eversible, paired copulatory organs.
The quadrate is carried by the horizontally-elongated squamosal, which rests loosely upon the skull.