山东沂沭断裂带早白垩世晚期恐龙足迹特征差异性

Differences in characteristics of dinosaur footprints in the late Early Cretaceous,Yishu Rifting Zone,Shandong Province

近些年来,在山东沂沭断裂带南部地区(莒南、临沭、郯城和东海)的下白垩统上部大盛群中发现了大量的恐龙足迹化石,而这些化石反映的足迹类型、形态大小、足迹踩踏深度等方面都存在有差异性。研究发现,在足迹类型方面,莒南地区以兽脚类和鸟脚类恐龙足迹为主,临沭、郯城和东海地区以蜥脚类恐龙足迹为主。足迹大小方面,莒南地区的兽脚类足迹可划分为类型Ⅰ和类型Ⅱ两种类型,而东海地区的恐龙足迹主要属于类型Ⅱ,但是莒南地区大多数足迹的趾间角要小于东海地区的,这可能是由于兽脚类恐龙属种的不同所造成的;莒南地区鸟脚类足迹绝大多数要小于临沭地区的鸟脚类足迹;郯城地区的蜥脚类足迹较小,而莒南、临沭和东海地区大多数蜥脚类足迹的大小较为相似,个别临沭和莒南地区的蜥脚类恐龙足迹较大。足迹踩踏深度方面,临沭、东海和郯城地区的足迹相比莒南地区的足迹要稍深,这与足迹形成在不同湿度、黏度、颗粒度的沉积物表面上有密切联系。基于上述研究认为,在早白垩世晚期,沂沭断裂带内生活着种类繁盛,数量庞大的恐龙动物群,联系到沂沭断裂带东部诸城地区早白垩世早期地层中也发现有大量的以兽脚类为主的恐龙足迹化石,推断在早白垩世,沂沭断裂带及胶莱盆地当时为一个理想的恐龙生存、繁衍的栖息地。同时,山东早白垩世大量恐龙足迹化石的发现也为整个华北甚至东北亚地区晚中生代恐龙属种的分布、演化以及古地理研究提供了丰富的材料和信息。

In recent years, abundant dinosaur footprint fossils have been discovered in the Lower Cretaceous （Dasheng Group） , the south of Yishu Rifting Zone, Shandong Province. Based on our re search, many different features of these footprints, including footprint types, morphology, depth of foot prints, etc., have been noticed and listed as follows： （1） As for the footprint makers, theropod and or nithopod tracks were dominant in Junan County, while in Linshu, Tancheng and Donghai, the sauropod tracks were primary. （2） As for the footprint size, the theropod footprints from Junan were divided into Type I and Type II , but in Donghai, only the Type II were present. In addition, the digit angle of theropod footprints in Junan is smaller than that in Dongbai, which may be caused by different dinosaur species. The ornithopod footprints from Junan are smaller than those of Dongbai. Moreover, the sauropod footprints are small in Tancheng, but are similar to those of Junan, Linshu and Donghai. （3） Because of the diverse humidity, viscosity and sediment granularity, the depth of footprints from the Donghai, Tancheng and Junan are various. Based on all the abovementioned new discovery of dinosaur footprints in Zhucheng, east of the Yishu Rifting Zone, in early Early Cretaceous, we conclude that a large and pros perous dinosaur fauna lived in Yishu Rifting Zone in the Early Cretaceous. Furthermore, the dinosaur footprints from Shandong Province in the Early Cretaceous were excellent materials for deeply research on distribution and evolution of the dinosaurs and palaeogeography in the Late Mesozoic of the North China and even the Northeast Asia.