Dinosaur facies in the Japanese Cretaceous based on molluscan paleontology

1.在日本中部Tetori地区东部发现了早白垩世细长脚趾恐龙足迹。根据生物测定分析，它们是小的、两足的和三足的印记，归属于Toyota amasauripus masuiae ichnogen和ichnosp.nov。在日本恐龙足迹中，33个个体的足迹密度是最高的。这也是日本报道的第一个群居恐龙的轨道证据。甲龙似乎代表了一种相对丰富的小型两足恐龙跑道制造者。由于在轨道承载层中没有发现骨骼，这些脚印增加了我们目前对恐龙动物群的了解。在上侏罗统至下白垩统Tetori群的多个层位中，陆相Mlluscan物种相当丰富。在其南部分布中(日本盖夫县中部的北部)，有一个典型的群体部分，与…有一种指法关系陆相地层和海相地层之间存在更多的离子作用。我分析了该群中间部分的软体动物组合，以了解海洋向非海洋过渡环境中的攻击学和其他特征。在Matsukawa和Ido(1993)定义的5个非海生软体动物组合中，有4个被识别：[1]Ostreidae gen.et sp.indet.-Myene(Mesocorbilla)teoriensis[表型J]组合，[2]Myene(Mesocorbilla)teoriensis[表型J]组合，[3]Sphaerium sp.组合体和[4]Plicatounio(P.)Naktongensis-Trigonioids(WAkinoa)Tetoriens组合。这些组合反映了从浅水到淡水的某些等级的环境，并且组合的物种组成随着盐度的变化而变化(Matsukawa和Ido，1993)。群的中段显示了由闭塞到淡水的环境。非海生软体动物物种在日本的上侏罗统到下白垩统的沉积物中很常见。许多物种在早白垩世时期揭示的生态指数比年代学指数更强。较少

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