The Llandovery (Silurian) conodont species diversity on the Upper Yangtze Platform, South China

Conodonts are one of the stratigraphically most important fossil groups in the Silurian Period. We examine the regional diversity dynamics of the Llandovery condonts on the Upper Yangtze Platform. The data set of 41 species from seven sections is compiled from the Geobiodiversity Database. Four measures of taxonomic richness based on zonal counting are used to demonstrate the conodont diversity change. The CONOP (Constrained optimization) program is used to build up a more precise composite sequence, which provides the data for comparative analysis of diversity change. Conodont richness keeps growing from the Ozarkodina aff. hassi Zone through the Ozarkodina obesa Zone to the Ozarkodina guizhouensis Zone and reaches a peak at the fourth zone, the Pterospathodus eopennatus Zone. This significant growth was followed by a rapid decrease, which probably represents an extinction in the mid-Telychian. This extinction event can also be observed in other fossil groups such as graptolites and chitinozoans based on recent studies.