Earth & Life (http://www.geofinds.com), (2006-10-1), 1(1): 1--6.

Wu Ya Sheng^1*

1. Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029 wys@mail.igcas.ac.cn

Abstract  Earlier study on the Permian-Triassic boundary (PTB) sections in Meishan proposed that there were no mass extinction in conodonts across the PTB. Based on after-revision conodonts from the PTB sections in Meishan, Shangsi, and Kashmir, this study shows that there was a mass extinction in conodonts at the end of the Permian (between beds 26 and 27a of Meishan), which is later than the mass extinction of most other invertebrate groups at between beds 24e and 25 of Meishan. There are three evolutionary events in conodonts across the PTB. The first occurred at between beds 26 and 27a of Meishan, where most Clarkina components were replaced by Hindeodus components. The second event occurred at between beds 27b and 27c, where Hindeodus components with big cusp appeared. The third event occurred at between beds 27d and 28, where most Hindeodus components of Bed 27d disappeared.

Keywords: conodont; Permian-Triassic boundary; evolution; mass extinction

1. Introduction

The study of the geological events across the Permian-Triassic boundary (PTB) needs a time reference and conodont zones defined by the evolutionary events of conodonts (Yin et al., 1998, Yin et al., 2001.) are the most widely used relative time reference, except for absolute ages determined by zircon from the ash beds (Bowring et al., 1998., Mundil et al., 2004). The end-Permian mass extinction killed more than 90% of non-reef marine organisms (Erwin et al., 1993), 100% of reef marine organisms (Wu et al., 2002.), 70% of terrestrial vertebrates, and most land plants (Retallack, 1995). This death roll includes nearly all marine organisms but not conodonts. So, studies are need to find was there any mass extinction in conodonts across the PTB.

Jin et al. (2000) deal with the extinction pattern of most invertebrate groups in Meishan sections and found that the mass extinction is a sudden extinction at 251.4 Ma followed by gradual decline of some more taxa in the later 1 Ma. Was the mass extinction of conodonts, if it was present, also a sudden event?

* WU YS: PhD degree from Chinese Academy of Sciences. Associate Professor of Institute of Geology and Geophysics, Chinese Academy of Sciences. Have been doing Researches on Permian reefs, Permian-Triassic boundary since 1988.

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