藏东昌都地区首次发现中侏罗世兽脚类恐龙行迹

藏东昌都地区阿涅塘化石点中侏罗世达布卡组滨湖相紫红色中-细砂岩中，发现以凸形迹完好地保存的4层恐龙足迹，包括Grallator类、大型兽脚类、小型兽脚类和小型蜥脚类等足迹类型，并构成两列完美的行迹. 组成行迹T1的4个Grallator类足迹被命名为Grallator anietangensis isp. nov.，对其进行了详细的形态学分析，并讨论了造迹恐龙的大小和运动状态，这是Grallator类足迹在西藏地区的首次发现. 组成行迹T2的9个大型兽脚类足迹被归为Theropoda igen. et isp. indet.，对该类足迹进行了形态描述和功能分析；这类足迹在中国是首次记录，其连续且清晰的尾迹表明造迹者并非处于正常运动状态，而是应对某种特殊境况的特别行为方式，即其正以昂起的前躯一边观察，一边以极低的速度前进，因前躯昂起，尾部相应下垂，从而留下尾迹. 两列行迹均显示出造迹者正沿古昌都湖岸前进. 中国迄今所发现的恐龙骨骼和Grallator类足迹化石主要表现为以西南地区为中心，再向四周不断发散的扩散模式，但Grallator类足迹化石综合提供的信息显示恐龙动物的扩散速度比骨骼化石反映的速度更快. 

First Discovery of Middle Jurassic Theropod Trackways in Changdu Region,Eastern Tibet of China

A new dinosaur track site, Anietang site, was discovered in Changdu region of eastern Tibet. The lithostratigraphy of this track site is mainly lakeside purplish red medium-fine sandstone of the Middle Jurassic Dabuka Formation. Four exquisitely convex track layers (footprint types including Grallator, large theropods, small theropods and small sauropods) and two perfect track-ways were found. Four sequential Grallator footprints that make up the T1 trackway are named Grallator anietangensis isp nov., and a detailed morphological analysis was performed on it. It is doubtless that the Grallator was found in Tibet for the first time, and the size and gait of track-maker are discussed. Nine large theropod footprints that make up T2 trackway are classified as Theropoda igen et isp. indet.. The current study has described the morphology of Theropoda igen et isp. indet., and it is determined that this kind of footprint is found for the first time in China. The consecutive and clear trail tracks of T2 indicate that the trackmaker was not in a normal gait, but a special behavior to deal with a particular situation. It is speculated that the trackmaker was detecting situation with its raised body while walking at a very low speed. The forequarters were raised, resulted in the tail to sag correspondingly, and left trail tracks. Both trackways show that the trackmakers were walking along the bank of ancient Changdu Lake. At present, the dinosaur skeletons and the Grallator footprints found in China all show a migration pattern with the Southwest China as the center and then spreading around. But the speed of dinosaur migration reflected by the Grallator footprints is faster than that of skeletons.