Observations on Ctenurella (Ptyctodontida) and the classification of placoderm fishes |
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Authors: | PETER L FOREY BRIAN G GARDINER |
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Institution: | Department of Palaeontology, British Museum (Natural History), London SW7 5BD;Sir John Atkins Laboratories, Biology Department, King's College, Campden Hill Road, London W8 7AH |
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Abstract: | The structure of the hyoid arch of the ptyctodont Ctenurella is described and discussed with reference to theories of jaw suspension in placoderm fishes. It is concluded that primitive placoderms had a modified hyoid arch but that the hyomandibular took no direct role in supporting the jaws. The relationships of ptyctodonts are discussed and it is concluded that they are placoderm fishes. Several different classifications of placoderm fishes are evaluated and are shown to be weakly based, chiefly because of lack of precise knowledge of character distribution. An attempt is made to produce a classification by using a simple cladistic computer analysis. The result highlights homoplasy in character distribution amongst traditionally recognized placoderm groups. |
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Keywords: | Ptyctodontida jaw suspension ptyctodont relationships placoderm classification cladistics Devonian |
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