四川西昌盆地白垩纪恐龙足迹群的新发现

    New discovery of Cretaceous dinosaur track fauna in Xichang basin, Sichuan Province

    • 摘要: 四川西昌盆地白垩系小坝组尚未发现骨骼化石记录,其白垩系恐龙动物群的信息全赖于足迹化石。2017年,在喜德县洛甘发现小坝组迄今最大型的恐龙足迹群。该足迹点保存了大量的兽脚类足迹。足迹保存条件较差,但具备了基本的形态学特征。总体来看,兽脚类足迹具有尺寸较小(8~13cm),中等中趾前凹(0.5~0.6)和第Ⅱ趾和第Ⅳ趾间较宽趾间角(70°~100°)的特征;少量足迹保存了跖骨垫。初步分析认为,洛甘兽脚类足迹与四川盆地夹关组的兽脚类足迹EubrontesGrallator形态类型相似,为两地在白垩纪中期具有类似的恐龙动物群的观点提供了新的证据。该发现对于西昌盆地的古气候、古地理和地层对比都具有重要的意义,足迹详细分类还有待进一步研究。

       

      Abstract: The dinosaur fossils haven't been recorded in Cretaceous Xiaoba Formation in Xichang basin, Sichuan Province. Hence, the dinosaur footprints provide crucial information for improving the understanding of the Cretaceous dinosaur assemblages. In April 2007, the authors discovered a new dinosaur footprint assemblage in Xiaoba Formation at Luogan Township, Xide County. The Luogan tracksite is poorly preserved, but it contains abundant theropod tracks with basic morphological features. In general, the small the-ropod tracks (8~13cm) are characterized by moderate mesaxony (0.5~0.6) and wide divarication angles between digits Ⅱ and Ⅳ (70°~100°), few of which developed metatarsal pads. The authors tentatively hold that the Luogan theropod assemblages are probably similar to Eubrontes and Grallator of Jiaguan Formation in Sichuan basin, which provides new evidence that these two areas had similar dinosaur faunae in Middle Cretaceous. This discovery is of great significance for paleoclimate, paleogeography and stratigraphic contrast in Xichang basin. Detailed classification of footprints needs further study.

       

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