The genus Amaltheus, one of the representative late Pliensbachian ammonoids, has biostratigraphic and paleobiogeographic significance in Japan. Four species, Amaltheus stokesi (Sowerby, 1818), A. margaritatus de Montfort, 1808, A. repressus Dagis, 1976, and A. orientalis new species, have been found in the Kuruma Group in central Japan; A. stokesi and A. margaritatus are also from the Toyora Group in southwest Japan. On the basis of taxonomic analysis of the genus Amaltheus, we distinguish two successive ammonoid biozones in the lower part of the Teradani Formation of the Kuruma Group: the Amaltheus stokesi–Amaltheus repressus and the Amaltheus margaritatus assemblage zones, in stratigraphic ascending order. This study also establishes the presence of the Amaltheus stokesi Assemblage Zone in the Higashinagano Formation of the Toyora Group. The stokesi–repressus and the stokesi assemblage zones correspond biostratigraphically to the Amaltheus stokesi Standard Subzone of the margaritatus Zone. The margaritatus Assemblage Zone is correlated with the Amaltheus subnodosus and Amaltheus gibbosus standard subzones. The Japanese early–middle late Pliensbachian ammonoid faunas are composed almost entirely of pan-Boreal and Arctic species of the genus Amaltheus. This faunal composition has an affinity with that of the Northeast Russian region, and thus suggests a strong paleobiogeographic relationship between East Asian and Northeast Russian faunas throughout this time interval.UUID: http://zoobank.org/5F08121F-1DAF-4B24-BCBE-B08F7101CF29

中文翻译：

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日本晚普林斯巴赫纪（早侏罗世）菊石Amaltheus：系统学、生物地层学和古生物地理学意义

属阿马尔修斯是具有代表性的晚普林斯巴赫纪菊石之一，在日本具有生物地层学和古生物地理学意义。四种，阿马尔修斯斯托克西（索尔比，1818 年），A.玛格丽塔德蒙福特，1808 年，A. 压制达吉斯，1976 年和A. orientalis在日本中部的久留马群发现了新种；A.斯托克西和A.玛格丽塔也来自日本西南部的Toyora集团。基于属的分类学分析阿马尔修斯，我们在 Kuruma 群 Teradani 组的下部区分了两个连续的菊石生物带：阿马尔修斯斯托克西–阿马尔修斯镇压和玛格丽塔阿玛尔修斯组合带，按地层升序排列。本研究还确定了存在阿马尔修斯斯托克西丰良集团东长野组集合带。这斯托克西–压抑和斯托克西组合带在生物地层上对应于阿马尔修斯斯托克西标准分区玛格丽塔图斯区。这玛格丽塔图斯组装区与结节下的阿马修斯和长臂猿标准分区。日本早中晚期普林斯巴赫阶菊石动物群几乎全部由该属的泛北方和北极物种组成阿马尔修斯. 这种动物群组成与俄罗斯东北部地区的动物群组成有密切关系，因此表明在这段时间间隔内东亚和俄罗斯东北部动物群之间存在很强的古生物地理关系。UUID：http://zoobank.org/5F08121F-1DAF-4B24-BCBE-B08F7101CF29