A research team comprising the Kunming Comprehensive Natural Resources Investigation Center of the China Geological Survey, the School of Resources and Environmental Engineering at Guizhou University of Science and Technology, and the Guizhou Geological Museum recently discovered a new genus and species of ammonite—a species named Guanling Guanling Ammonite—in the Xiaoa’ou Formation of the Carnian Stage of the Upper Triassic in Guanling County, Guizhou Province. This discovery not only enriches our understanding of ammonite biodiversity in southern China during the Late Triassic but also provides crucial evidence for the chronological classification of the Xiaoa’ou Formation.

Guanling Guanling ammonite is a medium-sized ammonite characterized by a semi-internal coiled shell. Its ventral transverse ribs are broad and forked, with approximately 10 small tubercles visible on each rib. Along the ventral margin, the tubercles alternate between small tubercles and prominent, raised tubercles near the chamber, while closer to the aperture, they arrange themselves into two distinct rows of small tubercles. Given that several features of this ammonite show high homology with certain ammonites from the Julian 2 substage of the Upper Triassic Carnian stage in Siberia and Western Europe, the research team concludes that the stratigraphic horizon yielding the Guanling Guanling ammonite should be assigned to the late Triassic Carnian Julian 2 substage.