In this section I have tried to outline the more important elements used in establishing a system of effective classification and at the same time to enlighten the layman to the “little things” that are a very important part of making a lizard a lizard. Although this chapter is brief, it is as complete as space allows and as accurate as possible.
Skull
In general discussions about the head of an animal, the upper portion is referred to as the cranium, while the lower part consists of the mandible. In lizards the foremost bone of the mandible is the dentary; it is at the foremost point of the dentary bone that the two halves of the mandibles are firmly united (the symphysis). The mandible articulates with the cranium at the quadrate bone, located near the rear of the cranium. The coronoid bone juts up behind the dentary bone and fits into a socket formed by the pterygoid bones of the cranium. The distance from the tip of the snout to the coronoid intersection determines the gape of the lizard.
In the mandible, teeth are found on the dentary bone; in the cranium they may be on the maxillary, premaxillary, palatine, or pterygoid bones. The teethe themselves may be pleurodont (along the side of the bone) or acrodont (along the crest of the bone). On some lizards thecodont teeth (fitting into sockets) are found, but along with one of the other types. The teeth may be pyramidal, conidal, flat, bicuspid, or tricuspid. They can be quickly and frequently replaced.
Between the maxillary, premaxillary, and septomaxillary, bones is a large gap in the cranium. This is in effect the internal nasal arch through which the nostrils draw air through the skull into the mouth. Another gap exists a little behind this.
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