Abstract
THE questions of the classification of the fishes and of the interrelationships of the different groups are occupying the attention of different zoologists. In such a study, which involves fossil forms, a consideration of the bones of the skull and their homologies must play an important part. The dermal bones among other skeletal structures, are often quite well preserved and so have received much attention. On the other hand, the neurocrania, being partly obscured by the dermal bones and only capable of study in particularly well-preserved specimens, are nothing like so well known although quite important. Hence the interest of a study of the neurocrania of some Jurassic Holostei recently made by Dr. Dorothy H. Rayner (Phil. Trans. Boy. Soc., B, 601 ; 1948). A special technique involving the grinding of the specimen and the taking of a series of transfers 0·1 mm. apart was elaborated from a previous method suggested by E. C. Case in 1937. An appendix describes the technique fairly fully, and it will probably be of use in other lines of work involving the sectioning and reconstruction of fossil material. In spite of considerable variation in the neurocranial ossifications, which differ among. closely related forms and apparently in tha same species with difference of age, there is, save in the supraoccipital and postotic regions, sufficient similarity to allow of broad homologies being drawn. This and other evidence adduced suggests that the Jurassic Holostei may be regarded as a natural group. Two particular points may be noted. There is sufficient similarity between the neurocrania of the Jurassic Lepidotus and the living Lepidosteus to suggest relationship between them, and in Caturus and Dapedius there is a lateral cranial canal without external opening to which, at present, no function can be assigned.
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Jurassic Holostei. Nature 163, 92 (1949). https://doi.org/10.1038/163092b0
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DOI: https://doi.org/10.1038/163092b0