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A Monograph of the Collignoniceratidae from Hokkaido Part Ⅳ : Studies of the Cretaceous Ammonites from Hokkaido and Saghalien-ⅩⅩⅠ

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概要 Part Ⅳ contains the systematic descriptions of the subfamily Texanitinae. The hitherto used framework of classification of the Texanitinae is considerably refined. Special attention has been paid on t...he ontogenetic development of the ornamentation, as well as on other characters. Comparisons of closely allied species are made to know the affinities between various taxa of generic rank. Protexanites is regarded as a fundamental genus of the subfamily and is subdivided into three subgenera, with the introduction of two new ones. Paratexanites, including the two subgenera, Paratexanites and Parabevahites, is probably derived from Protexanites. The ultimate origin of Texanites is in Protexanites. In the course of its ontogenetic development, the Protexanites- and sometimes Paratexanites-like characters are presented in many species. Those with fairly persistent ancestral characters in the inner whorls are grouped into a new subgenus of Texanites. Multiplication of the ventral ornament occurs in various lines of descent. A new genus [Pleurotexanites], Australiella, Menabites including the subgenera Menabites (s.s.) and Bererella, and Delawarella are directly or indirectly connected with Protexanites, Bevahites with Paratexanites (Parabevahites), and Submortoniceras with a certain group of Texanites. The described species from Hokkaido are altogether 20, of which 7 are new as listed in the contents below. They are mostly of Coniacian to Santonian ages. In connexion with the descriptions of the species from Hokkaido, comments are generally given on many previously described texanitine ammonites outside Hokkaido, establishing three new species and one new subspecies.続きを見る
目次 Systematic Descriptions (continued)

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登録日 2015.11.06
更新日 2021.02.18

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