The Dawangou auxiliary GSSP (Xinjiang autonomous region, China) of the base of the Upper Ordovician Series: putting global chitinozoan biostratigraphy to the test

Abstract. The Dawangou section, an auxiliary Global Stratoype Section and Point (GSSP) for the base of the Upper Ordovician Series, was sampled for chitinozoans. The 32 samples taken from the black shales of the Saergan Formation, spanning the Pterograptus elegans, Didymograptus murchisoni and Nemagraptus gracilis graptolite biozones, yielded 6536 chitinozoan vesicles. In addition to a diverse endemic assemblage, species important for international correlation were recovered, which enables the subdivision of the Saergan Formation into two chitinozoan biozones, one subzone and one provisionally recognized biozone: the Baltoscandian Laufeldochitina striata Biozone and the Laurentian Lagenochitina sp. A (sensu Achab, 1984) (/Belonechitina hirsuta) Biozone, and the Belonechitina tuberculata Subzone are recognized based on the presence of the index species, while the Baltoscandian Laufeldochitina stentor Biozone is provisionally recognized on the presence of Laufeldochitina sp. A aff. striata sensu Grahn et al., 1996 which has a range confined to the latter biozone. One new chitinozoan species is described: Cyathochitina giraffa sp. nov. and two species were assigned to a different genus: Belonechitina tuberculata comb. nov. and Hercochitina seriespinosa comb. nov.