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1 September 2010 The First Diplobelid Coleoid from the Late Cretaceous (Turonian) of Hokkaido (Japan)
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Abstract

Outcrops of the Turonian Saku Formation in the Obira region of Hokkaido (northern Japan) have yielded two breviconic phragmocones that represent a previously unknown species of Conoteuthis, a comparatively well known genus of diplobelid coleoids. The selected holotype of Conoteuthis hayakawai sp. nov. preserves a spherical protoconch that deviates slightly from the longitudinal axis of the phragmocone and is the first record of a protoconch in Conoteuthis. Conoteuthis hayakawai sp. nov. differs only slightly from the type species Conoteuthis dupiniana from the Hauterivian-Aptian of Europe and Conoteuthis azizi Fuchs et al. from the Cenomanian of southeastern India through its weakly developed dorsal saddles. Conoteuthis hayakawai sp. nov. is the youngest report as well as the first record of the Diplobelida from the Paleopacific. This new find considerably extends the stratigraphical and geographical occurrence of the Diplobelida. Phylogenetically, the genus Conoteuthis is considered to be an isolated group within the Diplobelida. With respect to the controversial origin of the Sepiida and Spirulida, morphological comparisons have shown that the genus Conoteuthis cannot be a potential stem-group of the Sepiida and/or Spirulida.

© by the Palaeontological Society of Japan
Dirk Fuchs and Shuji Niko "The First Diplobelid Coleoid from the Late Cretaceous (Turonian) of Hokkaido (Japan)," Paleontological Research 14(3), 169-178, (1 September 2010). https://doi.org/10.2517/1342-8144-14.3.169
Received: 14 December 2009; Accepted: 1 February 2010; Published: 1 September 2010
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