Gut contents in the Triassic ichthyosaur Panjiangsaurus from the Guanling biota in Guizhou

Abstract：Ichthyosaurs were one of highly successful groups adapted to the aquatic environment in the Mesozoic marine reptiles. However, only a few gut contents have been reported so far despite the fact that a number of articulated skeletons are known from this clade. Recently well-preserved ichthyosaur specimens have been found in the Guanling biota in the Lower Member of the Upper Triassic Xiaowa Formation in Guizhou, Southwest China. Among them, one specimen of Panjiangsaurus epicharis (YIGM V30016) with gut content is studied for exploiting the dietary habits of this taxon. The gut content is micrite with organic phosphatic biodetritus. The biodetritus is mainly composed of many small fish bone fragments with small quantity of bivalve shells. No gastroliths were found inside the gut contents. Panjiangsaurus, which had a long body and long tail and lacked blunt teeth, was probably an ambush predator, whereas post-Triassic ichthyosaurs were high-speed pursuit predators. It is indicated that Panjiangsaurus possibly fed on small fishes and bivalves, and that it did not need gastroliths for food trituration.