Ventral view |
The palatal surface is obscured laterally by the lower jaws, and medially by the trachea. Note, however, how far forward the anterior end of the trachea extends. The snake has the capacity to protrude or retract the opening of the airway. This allows the airway to be positioned well forward in the floor of the mouth (over the tongue) where it is less likely to be obstructed by large prey items. The python palate consists of five roughly parallel lines of bones – one in the midline, and two on each side. The midline series consists of the premaxilla, vomers, parasphenoid and posterior braincase (sphenoid, basioccipital). The sphenoid is narrow and ventrally keeled, retaining small ventrolateral processes that abut the dorsal edge of the pterygoids. These resemble the basipterygoid processes of other squamates, but are thought to be non-homologous (Kluge, 1991). Behind the sphenoid is the basioccipital. It is shorter with a prominent condyle (although few of these features are visible in this view). The lateral series comprises the maxilla and ectopterygoid. Running between lateral and median series on each side is an intermediate series comprising the palatine anteriorly and pterygoid posteriorly. Both bones carry sharp recurved teeth like those on the maxilla, so that Python has four parallel anteroposterior rows in the roof of its mouth. These tooth rows can move independently about the midline creating a ratchet system whereby the teeth of one side engage prey and pull it back into the mouth while the teeth of the opposite side disengage, move forward and lock onto the prey in a more anterior position before retraction begins. Thus prey is drawn systematically into the mouth and it is very difficult to escape. A medial process braces the maxilla against the lateral edge of the palatine, while a medial process from the palatine meets the ventral midline. Posteriorly, the pterygoid curves outwards to a weak, mobile, articulation with the quadrate (just visible flanking the posterior half of the trachea in this view). |