内蒙古鄂尔多斯早白垩世甲龙类胃石与鳞片印痕化石的发现

Discovery of the Early Cretaceous Ankylosaur Gastroliths and Scale Impressions from the Ordos Basin, Inner Mongolia, China

摘要: 内蒙古鄂尔多斯盆地北部早白垩世志丹群陆相沉积中产有丰富的脊椎动物化石，其中包含兽脚类、剑龙类和鹦鹉嘴龙类等恐龙类群。1件不完整的甲龙类化石最近发现于杭锦旗老龙豁子罗汉洞组中，该化石保存有一团胃石以及局部鳞片印痕。至少22枚坚硬且磨圆度较好的砾石保存在联合荐椎和左肠骨前方，砾石长径为20 mm至35 mm，显示该甲龙类大体呈原位保存的胃石的存在。在颈椎附近露出有面积约为40 cm2的鳞片印痕，单个鳞片基本上呈四边形、相互不接触不叠覆，面积多在6 mm2与12 mm2之间。该标本不仅代表了鄂尔多斯盆地早白垩世甲龙类化石的首次发现，也是我国第1例保存有胃石与鳞片印痕的甲龙类化石，在研究甲龙类的生态习性方面等具有较为重要的科学价值。

Abstract: The Early Cretaceous terrestrial Zhidan Group of the Ordos Basin, Inner Mongolia produced ab-undant fossil vertebrates including several dinosaur groups such as theropods, stegosaurs and psittacosaurids. Recently, an incomplete ankylosaur skeleton has been found from the Luohandong Formation at Laolonghuozi site, Hangjin Qi. Fortunately, a cluster of gastroliths and some area of scale impressions are clearly preserved. At least 22 pebbles are presented at the position just ahead of synsacrum. They are hard and rounded, with each pebble roughly 20 millimeters to 35 millimeters in long axis. These pebbles should be interpreted as gastroliths (stomach stones). More than 40 square centimeters of scale impressions are exposed near the cervical vertebrae. Each scale is generally trapezoid in outline, with the area varying from 6 square millimeters to 12 square millimeters. These scales are small and separate, compared with the relatively large and various shaped osteoderms in ankylosaurs. This specimen represents not only the first finding of ankylosaur dinosaurs among the Early Cretaceous vertebrate fauna in Ordos Basin, but also the first example of the ankylosaur gastroliths and scale impressions in China.