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A total of more than 40 tridactyl and didactyl tracks were preserved as natural casts on four fallen blocks of sandstone representing the Lower Cretaceous Jiaguan Formation of Gulin County in southeastern Sichuan Province, China. While several trackways can be distinctly followed, others are isolated imprints only. All have been flattened by overburden pressures. Tridactyl tracks are present with three size-classes being <10 cm, 10–20 cm and >20 cm in length. Morphologically they are similar to the ichnogenus Eubrontes, considering the relatively weak mesaxony. Eight of the tracks on one of the blocks are clearly didactyl and are here interpreted as representing large and medium sized dromaeosaurids. The largest track is about ∼30 cm long and comparable in size to the type of Dromaeopodus (∼28 cm), from the Lower Cretaceous of Shandong Province, which was the largest dromaeosaurid track previously reported. This report adds new data to the growing number of dromaeosaurid tracksites reports from China, and from the Jiaguan Formation, suggesting that this theropod group had a preference for fluvial paleoenvironments. 相似文献
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四川华蓥山浅层杂卤石钾矿地质特征及其成因意义 总被引：2，自引：0，他引：2
四川浅层杂卤石钾矿分布于华蓥山背斜北倾没端下中三叠统之硬石膏岩层中。杂卤石钾矿体呈透镜体状分布,伴有多钙钾石膏和硫锶钾石,为富钾溶液交代作用形成。浅层杂卤石钾矿具有资源及固态可溶性钾盐找矿的指示意义。 相似文献
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The study of the external and internal shell characters of Pironaea milovanovici Kühn, as well as of their ontogenetic and intra-specific variability, observed on abundant, well preserved, and matrix-free specimens from Tavernes de la Valldigna, Valencia province, Spain, revealed that other Pironaea species (e.g. P. bacevicensis Milovanović, P. petkovici Milovanović, Sladić-Trifunović, and Grubić, P. postdalmatinica Pamouktchiev, P. signumpraeverta Pamouktchiev, and Pironaea sp. ex gr. polystyla in Lupu), based on one or a very small number of specimens, are junior synonyms of P. milovanovici Kühn. The pore and canal system of the left valve is described in detail, based on differently weathered valves and differently oriented sections; it is constrained by the presence of secondary pillars in both valves. Being the pore and canal system and its relation with the secondary pillars relatively simple and well understood in P. milovanovici, by comparison, an interpretation of these structures in more complex multiple-fold Hippuritidae such as those of the Americas is hypothesized. 相似文献