Skulls of Falconiformes Ventral aspect of the skull

• Fig. 1. Skull of Catharistes urubu, showing the type of desmognathism peculiar to the Cathartae wherein the palate is bridged by the union of the horizontal plate of the nasal septum with a pair of septo-maxillary spurs. Note also the presence of basipterygoid processes.
• Fig. 2. Skull of Elanus caeruleus. The palate is schizognathous. Herein the maxillo-palatines have increased in size, whilst the septo-maxillary spurs have completely disappeared. The nasal septum is more complete than in Catharistes and may be seen lying in the middle line of the anterior palatal vacuity. Above the inflated region of the maxillo-palatines it sends downwards a feeble pair of spurs which nearly touch the maxillo-palatines. The basipterygoid processes are represented only by a pair of minute prickles.
• Fig. 3. Skull of Falco minor. The palate is completely desmognathous. Note the peculiar form of the vomer, and its relation to the maxillo-palatines. The antrum of the maxillo-palatines is reduced to the merest vestige.
• Fig. 4. Skull of Circaetus gallicus. The palate is schizognathous, and an exaggeration of that seen in Elanus. Fusion of the approximated maxillo-palatines and a downgrowth of and addition to the substance of the nasal septum would give the palate of Falco. Note the palatal aperture of the antrum.
• Fig. 5. Skull of Pseudogyps bengalensis. The palate is indirectly desmognathous. The palate is bridged by the fusion of the greatly swollen nasal septum with the widely separated maxillo-palatines.
• Fig. 6. Skull of Gypaetus barbatus. The palate is indirectly desmognathous, and of the same type as in Gyps, but from its less specialized condition shows how the palate of Gyps has been derived. The vomer is present, the maxillo-palatines are of great length and widely separated, whilst the nasal septum can be traced throughout its entire length.
• Fig. 7. Skull of Serpentarius serpentarius. The palate is schizognathous, since the maxillo-palatines, though closely approximated, do not fuse. Fusion would produce the completely desmognathous type of Falco. The antrum of the maxillo-palatiues is of great size, and the maxillo-palatine processes are large.

A.p.v. = anterior palatal vacuity.
bp.p. = basipteiygoid process.
mx.p. = maxillo-palatine process.
n.s. = nasal septum.
p.a. = palatine.
p.a.a. = palatal aperture of antrum.
pt. = pterygoid.
s. = spur of nasal septum.