Cranial anatomy of the Lower Jurassic shark Hybodus reticulatus (Chondrichthyes, Elasmobranchii) : with comments on hybodontid systematics / John G. Maisey. American Museum novitates ; no. 2878
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Date
1987
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New York, N.Y. : American Museum of Natural History
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Abstract
"Hybodus reticulatus Agassiz, from the Lower Jurassic of England, is considered to be the type species of Hybodus. It is founded on skeletal fragments and associated teeth. The cranial anatomy is described from several incomplete specimens, including some of the type material. Two specimens from the Upper Lias of Germany are referred to H. cf reticulatus. Comparisons are made with the Lower Cretaceous Hybodus basanus, whose cranial morphology is more completely known. The neurocranium and jaws are similar in these species, suggesting that many of the anatomical peculiarities noted in the ethmoid and otico-occipital regions of H. basanus characterize a larger group of hybodontid sharks, including the type species of Hybodus. Some differences are noted in the detailed arrangement of the lateral otic process, cephalic spines, and ethmopalatine articulation in H. reticulatus and H. basanus. These differences are considered to be of systematic importance; H. basanus and H. fraasi are placed in a new genus, Egertonodus, on the basis of several differences from H. reticulatus. The genus Hybodus remains an assemblage of nominal species, but increased anatomical data will gradually alleviate this situation. A list of genera retained within the Hybodontidae is given. Hybodontid tooth histology is reviewed, and forms the basis of a phylogenetic hypothesis which is open to falsification by other anatomical data"--P. [1].
Description
39 p. : ill. ; 26 cm.
Includes bibliographical references (p. 36-39).
Includes bibliographical references (p. 36-39).
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