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| Abstract |
One of us (T. M., 1970) once described two ammonites belonging to Hourcquia and Pseudobarroisiceras under different families and their exact geological ages were uncertain. In this paper two new speci...es of these genera are described on the material from the Upper Turonian of the Haboro area, northwestern Hokkaido. Also the age of the previously described specimen of P. nagaoi is revised to the Upper Turonian on the basis of a revised biostratigraphy of the Turonian and Coniacian of the Ikushumbets area, central Hokkaido. The described new species have several diagnostic features which show an intimate relationship between the two genera and also some affinity with Mesiaporites and Neoptychites. To sum up, we concluded to group at least the three genera Hourcquia, Mesiaposites and Pseudobarroisiceras into the subfamily Hourcquiinae of the Vascoceratidae. They lived in the Turonian, but whether Hourcquia and Pseudobarroisiceras persisted to the Coniacian or not should be worked out in the future．show more
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25_02_p229