Premaxillae of Bats
Identifying Bats
The premaxilla
The premaxilla is a convenient character for classifying bats. It varies among families in the size of its two components, the palatal and nasal branches, and in whether the nasal branches are fused to each other at the midline, or whether they are fused to the adjacent maxillae. Also, in some cases the palatal branches help define a pair of foramina at the anterior end of the palate; these too may be diagnostic.
The difficulty with using the premaxilla, or characteristics of any of the other bones that make up a bat's skull, is that early in development the cranial bones fuse together and obliterate their sutures. Nevertheless, because the premaxilla carries the incisors, and because it is so distinctive in some families, it can usually be recognized and is well worth studying. In the table that follows, examples of the main conformations of the premaxilla are shown. Whenever possible, young bats that still show at least traces of sutures were photographed. In some instances, I have tinted one premaxilla greenish to make it stand out, and in a few photographs I've labelled palatal or nasal branches.
Clicking on any image in the table below will give you an enlargement of the photograph.
(premaxillae well developed, nasal branches mostly free, palatal branches small) |
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(premaxillae well developed, similar to Pteropodidae) |
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(premaxillae lack palatal branches) |
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(premaxillae tiny and threadlike, usually lost in preparation) |
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(premaxillae with only palatal branches) |
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(premaxillae complete, fused to each other and maxillae, palatal branches isolating two palatal foramina) |
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(premaxillae separate, lacking palatal branches) |
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(premaxillae with nasal branches; with or without palatal branches) |
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