ISSN:0368-2935    

DOI:10.1111/j.1096-3642.1923.tb00044.x

出版商:Blackwell Publishing Ltd    

年代:1923

数据来源: WILEY

摘要:

SUMMARYThis paper includes the first complete accounts of the circumorbital region and opercular apparatus ofDipterus valenciennesi, and of the lower jaw ofD. platyeephalus.It gives very nearly complete descriptions of the skull, lower jaw, and clavicular apparatus ofSagerwdusandCtenoduswhich much extend our knowledge of these fish. In it the structures of the anterior end of the rare fishUronemusandConchopomaare described and figured for the first time.Dipterusis shown to be directly comparable with Osteolepids in the structure of the opercular apparatus and the lower jaw, in addition to the many previously known resemblances. It is thereby shown that, as its early date would indicate, it is the most primitive known Dipnoan.CtenodusandSayenodusprove to be closely allied, and a detailed comparison shows so great a similarity between the latter fish andCeratodusas to leave no doubt that it is essentially ancestral to it.UronemusandConchopomaresemble one another only in the reduction in them of the tooth‐plates to isolated denticles. In the structure of the palate and of the roof of the head they differ so much that they must represent widely‐separated stocks.In the main, the trends of Dipnoan development suggested by Watson and Day are confirmed. It is, however, pointed out that the structure of the neural cranium of the Osteolepids, as described by Bryant inEusthenopteron, is such that the Dipnoi cannot be direct descendants of that group, but that with it and the Amphibia they arose together from common ancestors at a time before the Middle Devon

ISSN:0368-2935    

DOI:10.1111/j.1096-3642.1923.tb00045.x

出版商:Blackwell Publishing Ltd    

年代:1923

数据来源: WILEY