The ammonoid Gonioclymenia fauna from the Upper Devonian (upper Famennian) of western Junggar, northwestern China

摘要

The Upper Devonian of western Junggar, Xinjiang, northwestern China bears abundant marine fossils and has attracted much attention with respect to palaeontological and stratigraphical studies. However, the records of ammonoids are sparse and the previously established assemblages need to be supplemented or emended through further collections. Here, we describe the Gonioclymenia fauna from the Wulan Member of the Hongguleleng Formation based on thorough and systematic sampling, including Gonioclymenia junggarensis n. sp., a member of the Gonioclymenia subcarinata Group, an evolute clymeniid, Cymaclymenia sp., and an indeterminate species of the Sporadoceratidae or Prionoceratidae. The strata bearing the Gonioclymenia fauna in western Junggar can be correlated with the upper Famennian UD V‐A2 to V‐C of the Clymenia Ammonoid ‘Stufe’, approximately corresponding to the Bispathodus aculeatus aculeatus Conodont Zone (former Middle expansa Zone). The Gonioclymenia species from western Junggar indicate close relationships with Europe and North Africa, while the latter two regions show a higher abundance and species diversity within the genus. New specimens described here enrich the composition of the Gonioclymenia fauna of western Junggar, and shed lights on the stratigraphic correlation and subdivision of the Upper Devonian in this region at a fine resolution.