Dinosaur facies in the Japanese Cretaceous based on molluscan paleontology

1.日本中部铁取地区东部发现早白垩世细趾双足恐龙足迹。根据生物统计学分析，它们是小型的、两足的和三趾的足迹，被分配给富山龙属masuiae ichnogen和ichnosp.nov。在日本的恐龙足迹遗址中，富山龙的33个个体的足迹密度最高。这也是日本首次发现群居恐龙的足迹证据。富山龙似乎代表了一种相对丰富的小型两足恐龙足迹制造者。由于没有骨骼已知的轨道轴承床，脚印增加了很多我们的知识，恐龙动物群在这个时候。在上侏罗统-下白垩统Tetori群的许多层位中，都有相当丰富的非海相微流虫种。在其南部分布区（日本岐阜县中部的北方），有具指交关系的岩群的典型剖面， ...更多信息 非海相地层与海相地层之间的电离作用。我分析了组的中部的软体动物组合，以了解海洋到非海洋过渡环境中的埋藏和其他特征。在Matsukawa和Ido（1993）定义的五个非海洋软体动物组合中，有四个被确认：[1] Ostreidae gen.et sp. indet. Myrene（Mesocorbicula）tetoriensis [Phenotype J]组合，[2] Myrene（Mesocorbicula）tetoriensis [Phenotype J]组合，[3] Sphaerium sp.组合和[4] Plicatounio（P.）naktongensis-Trigonioides（WAkinoa）tetoriensis组合。这些组合反映了从回水到淡水的一定等级的环境，组合的物种组成随盐度而变化（Matsukawa和Ido，1993年）。组中部剖面为半淡水-淡水环境。非海洋软体动物物种在日本的上侏罗纪至下白垩纪沉积物中很常见。许多物种在早白垩世时期表现出比年代学指标更强的生态指标。少

1. Early Cretaceous slender-toed bipedal dinosaur tracks are reported from the eastern part of the Tetori area, central Japan. They are small, bipedal and tridactyl impressions assigned to Toyamasauripus masuiae ichnogen, and ichnosp.nov.based on biometric analysis. Thirty-three individuals to Toyamasauripus masuiae show the highest density of footprints of any dinosaur track-sites in Japan. This is also the first trackway evidence of gregarious dinosaurs reported from Japan. Toyamasauripus masuiae appears to represent a small bipedal dinosaur track-maker that was relatively abundant. As no bones are known from the track-bearing beds, the footprints add much to our knowledge of dinosaur faunas at this time.2. Nonmarine mlluscan species are rather abundant in many horizons in the Upper Jurassic to Lower Cretaceous Tetori Group. In its southern distribution (the northern part of the Gife Prefecturecentral Japan), there is the typical section of the Group that have an interfingering relat … More ionship between nonmarine and marine strata. I analyzed molluscan assemblages in the middle part of the group to understand the taphonomic and other features in marine to nonmarine transitional environments. Four assemblages of nonmarine molluscs among that of five defined by Matsukawa and Ido (1993) are recognized : [1] Ostreidae gen.et sp.indet.-Myrene (Mesocorbicula) tetoriensis [Phenotype J] assemblage, [2] Myrene (Mesocorbicula) tetoriensis [Phenotype J] assemblage, [3] Sphaerium sp.assemblage and [4] Plicatounio (P.) naktongensis-Trigonioides (WAkinoa) tetoriensis assemblage. These assemblages reflect certain grades of environments from backish- to fresh-water, and the species composition of an assemblage varies with salinity (Matsukawa and Ido, 1993). The section of the middle part of the group shows from backish- to fresh-water environments.3. Nonmarine molluscan species are common throughout Upper Jurassic to Lower Cretaceous sediments in Japan. Many species reveal ecological indices more strongly than chronological indices during early Cretaceous time. Less