The marine conodont fossil species, Hindeodus changxingensis Wang, that has a distinctive morphology, is restricted to a very narrow stratigraphic interval essentially from the Permian-Triassic extinction event through the internationally recognized boundary and into the very earliest Triassic. The species is geographically widespread in the Tethyan Region, from Italy to South China, and serves as a characteristic index fossil to reliably identify this short but critical interval that encompasses the greatest mass extinction of life on earth and the boundary between the Paleozoic and Mesozoic Eras. ?? 2007 Nanjing Institute of Geology and Palaeontology, CAS.