The lower jaw is slender, nearly straight, 2-3 and without a coronoid process or inflected angle.
Supra-angular and coronoid splint-bones serve for the insertion of part of the temporal or masseter muscle.
No ectopterygoid pterygoid not extending to quadrate; no supratemporal or squamosal; prefrontal forming a suture with nasal; coronoid present; vestiges of pelvis present.
Coronoid present, prefrontal in contact with nasal.
Coronoid absent; squamosal present.
The mandible is toothed but has no coronoid bone.
The rest of the snakes are supposed to have started from some primitive, nondegenerate, therefore boa-like group, leading by loss of the vestiges of the hind-limbs and loss of the coronoid bone of the of which, for instance, T.
The prefrontal bones are still in contact with the nasals as in the previous families, but the coronoid bones of the mandibles are absent as in the remaining families, and this loss also occurs in the Boine Charina.
- Maxillaries horizontal and forming the greater portion of the upper jaw, which is toothed like the lower jaw; coronoid of mandible absent.
The lower jaw is characterized by its abruptly narrowed and rounded front part supporting the pair of large in cisors, as well as by the small size of the coronoid process, and the great development of the lower hind, or angular, portion.
And its coronoid process slender.
The spiny mice, Acornys (or Acanthomys), of Western Asia, Cyprus and Africa, take their name from the fur being almost entirely replaced by flattened spines, and are further distinguished by the rudimentary coronoid process of the lower jaw.