Chitinozoans from the Tremadocian graptolite shales of the Jiangnan Slope in South China

In the Nanba section of the Yiyang area in the Hunan Province (South China terrane), chitinozoans were recovered from three Tremadocian graptolite biozones (the Adelograptus tenellus, Aorograptus victoriae and Araneograptus murrayi biozones). Three genera and 12 species are identified from 16 different stratigraphical levels. Three chitinozoan biozones are distinguished, based on the Early Ordovician index species Lagenochitina destombesi Elaouad-Debbaj, 1988, Lagenochitina esthonica Eisenack, 1955 and Euconochitina symmetrica (Taugourdeau and de Jekhowsky, 1960). Together with coexisting graptolites, these chitinozoans are used for precise correlation at both regional and global scales. The fossiliferous strata of the Yiyang area allow us to calibrate the earliest chitinozoan biozones versus the reference graptolite biozones. The presence of the earliest specimen of L. destombesi in the lowest sample is doubtful, but an unidentified specimen of ?Conochitina, is found at the same level, and this taxon could potentially represent the oldest chitinozoans, if it can be proven to appear below L. destombesi.

► Three chitinozoan biozones are distinguished from the graptolite shales. ► Detailed calibrations between the chitinozoan and graptolite biozones are suggested. ► Precise regional and global correlations are possible based on chitinozoans. ► Specimens of ?Conochitina might, tentatively, represent the earliest chitinozoans.