Abstract
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.
Highlights
The Llandovery conodont-bearing strata are widely distributed on the Upper Yangtze Platform, South China
The conodont fauna and the biozonation of the rocks were first studied by Zhou et al (1981) based on the material from the Leijiatun section in the Guizhou Province
Chen et al (2000) reported the occurrence of only one conodont species, Amorphognathus ordovicicus from the Normalograptus extraordinarius Zone at the Wangjiawan North section. This is the only record of the conodont fauna during the mass extinction in South China
Summary
The Llandovery conodont-bearing strata are widely distributed on the Upper Yangtze Platform, South China. We used the CONOP.net version 1.0 to create the best-fit composite standard sequence which provides the highest possible stratigraphic resolution and is used to generate the ‘unbinned’ richness curve. This new version was programmed in the C# language by Junxuan Fan, Xudong Hou and Peter M. Chen et al (2000) reported the occurrence of only one conodont species, Amorphognathus ordovicicus from the Normalograptus extraordinarius Zone at the Wangjiawan North section This is the only record of the conodont fauna during the mass extinction in South China. It probably represents a new mass extinction of the conodont fauna in the middle Telychian
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