北海道白亜系産ローマニセラスの 1 種

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An ammonite specimen which can be identified with Romaniceras kallesi (ZAZVORKA), known from the Middle Turonian of Europe, was obtained from the Middle Turonian of the Obira area of northwestern Hokkaido. It is described and illustrated in this paper, as it is the first record of R. kallesi from the northwestern Pacific region. The Obira specimen is somewhat larger than the hitherto described specimens from Europe. Some of the umbilical tubercles are nodose and strong on its body-chamber, and the suture is best shown in this specimen. We have noticed that the holotype of Romaniceras pseudodeverianum (JIMBO, 1894) somewhat resembles this specimen and also an example of R. kallesi from Spain described by WIEDMANN (1960). We suggest that the two species are closely allied to each other or that R. kallesi (ZAZVORKA, 1958) could be a synonym of R. pseudodeverianum (JIMBO, 1894). This should be determined through a future study of the variation of this (or these) species.
国立科学博物館の論文