贵州兴义中三叠世拉丁期兴义动物群粪化石*

粪化石是重要的遗迹化石, 其内含物信息可为讨论生物行为、生理、相互关系、古环境等提供重要证据, 进而对恢复和重建地质历史时期的生态系统等有重要意义。本文首次报道了贵州省兴义市泥麦古剖面中三叠世拉丁期兴义动物群化石层第35自然层的7种不同形态的粪化石。通过观察粪化石的内含物情况, 发现其主要由贵州龙骨骼和鱼鳞组成，极少含有无脊椎动物碎片, 表明粪化石来源于非壳食性的肉食性动物。依据粪化石的尺寸、缺少螺旋结构及相对较小的内含物碎片等信息, 排除动物源是无脊椎动物、大型肉食性鱼类及大型鱼龙类的可能。结合兴义动物群下部化石组合海生爬行类实体化石的信息, 进一步推断所研究粪化石的动物源应为非鱼龙的海生爬行动物，很可能是幻龙类、鸥龙类或海龙类。本文报道的7种形态的粪化石显示该下部化石层中的海生爬行动物之间至少存在1级营养等级的差异, 这为恢复和重建中三叠世拉丁期海洋生态系统提供了重要依据。另外微生物的参与及泥质含量较高的厌氧环境使得该层的粪化石保存完好。

Coprolites from the Ladinian (Middle Triassic) Xingyi Fauna, Xingyi, Guizhou Province

Coprolites (fossilized faeces) are important paleobiological source for inferring diet, behavior and physiology of the source animals and predator-prey interactions among animals, and thus pivotal in reconstructing the trophic structure of paleoecosystem. Abundantly and exceptionally preserved coprolites are documented from the 35th layer of the Ladinian (Middle Triassic) Xingyi Fauna in the Nimaigu section, Xingyi, Guizhou Province and are categorized into seven morphotypes for the first time. Information about the inclusions was obtained by optical microscope and scanning electron microscope. The inclusions mainly consist of bone fragments of Keichousaurus hui and fish scales. Fragments of invertebrates are rare. The size of coprolites and the absence of spiral-shaped structure, together with relative small fragments included in coprolites, suggest that the producers are carnivorous marine reptiles. Taking information about the lower marine reptile assemblage of Xingyi Fauna into account, the producers might include Nothosaurus, Lariosaurus or Thalattosauria. The seven morphotypes of coprolites indicate the existence of at least one trophic level discrepancy among marine reptiles, which provides important information for the reconstruction of marine ecosystem in the Ladinian. In addition, the presence of Gram-negative bacteria and the anaerobic environment with high content of mud enhance the preservation of coprolites.