Pharyngeal denticles (placoid scales) of sharks, with notes on the dermal skeleton of vertebrates. American Museum novitates ; no. 2415
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Date
1970
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New York, N.Y. : American Museum of Natural History
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Abstract
"Within the buccopharyngeal cavity of many Recent sharks, there occurs a well-developed dermal skeleton, consisting of numerous, independent, non-growing denticles (placoid scales). It is apparent that the extent of this dermal skeleton, from the jaw margin to the pharyngo-esophogeal boundary, is a feature primitive for the Gnathostomata. Secondary reductions in the extent of this dermal skeleton are apparent in some Recent sharks. In others, pharyngeal denticles participate in the formation of specialized structures (pharyngeal pads), apparently analogous to the consolidated pharyngeal tooth plates of teleostomes. These observations lead to the hypothesis that the dermal skeleton of modern elasmobranchs is primitively subdivided, that is, in a primary micromeric condition. The relevance of this hypothesis is discussed in the context of a comparative theory of the dermal skeleton of vertebrates"--P. 24.
Description
26 p. : ill. ; 24 cm.
Includes bibliographical references (p. 24-26).
Includes bibliographical references (p. 24-26).
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