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

Coprolites (fossilized faeces) are important paleobiological sources for inferring diet, behavior and physi-ology of animals that produced them and predator-prey interactions among animals. Therefore, coprolites are pivotal in reconstructing the trophic structure of a 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 an optical microscope and a scanning electron microscope. The inclusions mainly consist of bone fragments of Keichousaurus hui and fish scales. Fragments of invertebrates are rare. The size of the coprolites and the absence of spiral-shaped structure, together with relatively small fragments of the inclusions in the coprolites, suggest that the producers are carnivorous marine reptiles. Taking the information of 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. This result provides important information for the reconstruction of the marine ecosystem in the Ladinian. In addition, the presence of bacteria and the anaerobic environment with high content of mud may have enhanced the preservation of coprolites.

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