A minute freshwater pycnodont fish from the Late Cretaceous on the southern margin of the Junggar Basin: Palaeoecological implications

Vertebrate fossils are abundant in sandy mudstones of the Cretaceous Donggou Formation in the Sikeshu area, southern margin of the Junggar Basin, Xinjiang. Here, a few pycnodont remains from the Sikeshu area are described. Isolated elements are identified as a fragment of vomer and a fragment of prearticular referred to Xinjiangodus gyrodoides. These specimens are very small, corresponding to small pycnodont individuals. The larger specimens found in the Late Cretaceous in the United Kingdom, Spain, Morocco, and the United States were mostly from marine sediments, whereas the small specimens described here lived in continental paleoenvironments. The fossils are buried in situ, and their preservation methods involve carbonaceous pressing film and carbonate mineralization, of which carbonate mineralization is the main method. This research result fills the gap in Cretaceous Stenodon data in the Junggar Basin and provides important fossil data for the study of Cretaceous Stenodon in the Junggar Basin and even in Central Asia. This study provides a new perspective for understanding the paleoecology of inland lakes in western China at the end of the Cretaceous.