| Abstract |
I describe in this paper two uncommon keeled ammonites, from the Upper Cretaceous of Hokkaido and South Saghalien, which have been unsettled in their systematic position. One is Pseusdobarroisiceras n...agaoi SHIMIZU, which is closely allied to a weakly ornate variety of Barroisiceras onilahyense but has an entire keel. It is assigned to the Barroisiceratinae, since it did not further give rise to other smoothly keeled ammonites to be grouped with it and since there are certain barroisiceratine ammonites which tend to show smoothing of the serrate keel in more or less late growth-stages. The similarity of Pseudobarroisiceras to Pseudoschloenbachia is superficial, because the latter is best ascribed to the Muniericeratidae, together with Taxasia, Lehmaniceras, etc. The other is a new species of Hourcquia, which is allied to but less typical than H. mirabilis COLLIGNON. It looks as if it were another smoothly keeled barroisiceratine ammonite related to Subbarroisiceras mahafalense BASSE. It is also superficially similar to Diaziceras tissotiaeforme SPATH, which, however, is a member of the Lenticeratinae.show more
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20_02_p305