898. ON HAUERICERAS DE GROSSOUVRE, 1894, A CRETACEOUS AMMONITE GENUS

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  • 898. 白亜紀アンモナイト属 Hauericeras について
  • 白亜紀アンモナイト属Hauericerasについて〔英文〕
  • ハクアキ アンモナイトゾク Hauericeras ニ ツイテ エイブン

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Abstract

Hauericeras de Grossouvre, 1894 is a well known ammonite genus which occurs widely in the Upper Cretaceous of various regions. There are, however, three unsettled problems which are studied in this paper with the results as follows : I. The type species, Ammonites pseudogardeni Schluter, 1872 is redefined with designation of GBI. 48 (whose suture figured in the original paper) as its lectotype. This conforms with the concept of the same species by Muller and Wollemann (1906). H. nodutum (Schluter, 1889) and H. buszii Wegner, 1905 fall in synonyms of H. pseudogardeni in the revised sense. II. The sexual dimorphism exists evidently in the well studied species of Hauericeras. This is demonstrated by excellent specimens of H. angustum Yabe from Japan acquired by S. T. and Y. K. and also some more material. In H. angustum macroconchs are twice (or more) as large as microconchs in diameter. The apertural margin is distinctly sigmoidal in both conchs and lappeted in microconchs. H. gardeni (Baily) is likewise dimorphic. Many of the described specimens of H. pseudogardeni are macroconchs which may attain to 420 mm in diameter, whereas H. mengedensis (Schluter) is probably a microconch of the same species. III. The phylogenetic origin of Hauericeras is probably in a subgroup of Puzosia which has compressed nearly flat-sided whorls and weak or short ribs. The projected short ribs remain on the ventral part of H. antiquum Collignon, a Coniacian species, whereas an incipient keel occurs in a Turonian species of Puzosia. The two subgenera H. (Hauericeras) and H. (Gardeniceras) can be distinguished by the maintennance or disappearance of the ventral or ventrolateral riblets or nodes. They probably reflect the evolutionary stages. The proposal to combine the Hauericeratinae with Puzosiinae into the family Puzosiidae is approved.

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