Middle-Late Ordovician chitinozoans from Songliang of Qiaojia, western South China, and their biostratigraphic implications

Ordovician chitinozoans are as yet inadequately documented from the western Yangtze Platform, South China. Here we present a systematic study on chitinozoans from a Middle-Upper Ordovician succession at Songliang of Qiaojia, northestern Yunnan, southwest-ern China. Altogether 34 species of 12 genera are identified from the upper Hungshihyen and the Huadan formations. The top of the Hungshihyen Formation yields typical Early and Middle Ordovician forms, for instance, Lagenochitina obeligis and Belonechitina chen-jiawuensis, with the latter only known from the lower Darriwilian in South China, thus suggesting an early Darriwilian age for this inter-val. The chitinozoans recovered from the Huadan Formation include Lagenochitina prussica and Spinachitina fossensis, both are mainly confined in Katian and sometimes ranging into younger strata. This indicates an age younger than the middle to late Darriwilian pre-viously determined for the Huadan Formation. However, conflicts exist in age assignment of the Huadan Formation based on chitino-zoan and other evidence, and further work is required.(c) 2021 Elsevier B.V. and Nanjing Institute of Geology and Palaeontology, CAS. All rights reserved.