Late Devonian–early Carboniferous ostracods (Crustacea) from South China: taxonomy, diversity and implications

Elvis Guillam,Sylvie Crasquin,Marie-Béatrice Forel,Junjun Song

doi:10.5852/ejt.2022.804.1689

Abstract

The impact of the late Devonian Hangenberg Event on ostracods is quantified for the first time from newly acquired data from the Blue Snake section, Guizhou Province, South China. Ninety–eight species belonging to 31 genera are identified and figured. Four new species are described: Clavofabella? lanshella sp. nov., Sansabella gelaohensis sp. nov., Cytherellina caerulea sp. nov., Sulcella baisuzhena sp. nov. The ostracod associations from the Blue Snake section document a significant drop in specific diversity as well as major changes in taxonomic composition through the Hangenberg Event. We here report the reduction of the proportion of Palaeocopida and the increase in that of Podocopida between the latest Famennian and the Tournaisian. The specific extinction and renewal rates are estimated at 44% and 62%, respectively. The main factor of the post–crisis renewal of ostracod faunas in the Blue Snake section appears to be the progressive diversification of the family Bairdiidae and was probably related to palaeoenvironmental changes. The characteristics of associations point to an increase of the water depth over the studied area, from a near–shore shallow environment during the latest Famennian to a deeper and more open offshore environment during the Tournaisian.

Highlights

The late Devonian witnessed two intense biotic events: the Kellwasser event close to the Frasnian–Famennian boundary (F–FB) and the Hangenberg Event (HE) close to the DevonianCarboniferous boundary (D–CB)
Because the renewal of ostracod faunas in the Blue Snake section was mainly linked to this diversification, we propose that the recovery was depending on the palaeoenvironmental changes
Ninety-eight species belonging to 31 genera have been retrieved from the Blue Snake section spanning the Famennian–Tournaisian transition in Dushan County, Guizhou Province, South China

Summary

Introduction

The late Devonian witnessed two intense biotic events: the Kellwasser event close to the Frasnian–Famennian boundary (F–FB) and the Hangenberg Event (HE) close to the DevonianCarboniferous boundary (D–CB). The Hangenberg Event, sometimes considered as severe as the Kellwasser event, impacted both marine and terrestrial ecosystems It impacted marine ecosystems and caused the disappearance of 85% of ammonoid genera (Becker 1993), about 30% to 50% of benthic neritic ostracod species (Kaiser et al 2016 after data from Casier et al 2004, 2005), about 60% (Holy Cross Mountains, estimated from data from Olempska 1997) to 66% (Thuringia, estimated from data from Blumenstengel 1993) of deeper species and about 50% of pelagic species (Walliser 1996). The specific extinction rate of these deep faunas is lesser in Puech de la Suque (Montagne Noire, France) with a value between 25% and 31.5 % (Casier et al 2001) and in Avesnois (North of France) than in the Holy Cross Mountains and Thuringia (Casier et al 2002) It impacted terrestrial ecosystems such as the Archaeopteris forests (Kaiser et al 2016) and Retispora lepidophyta flora (Streel et al 2000)

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