REVISED CLARKINA TAXONOMY BASED ON CONODONT SAMPLE-POPULATION APPROACH

A high-resolution Lopingian conodont biostratigraphic framework is necessary to resolve event correlation leading to the end-Permian mass extinction. This has been established in South China using a sample-population approach. Two different approaches, form species and sample-population species, have been used to identify species. The first method has been used from the beginning of conodont research; it identifies species based on one or two characters in a single or a few specimens. This method was popular for a long time because conodont animals were unknown and only a few specimens were obtained from rock samples. Abundant conodont specimens are now often recovered from a rock sample. Abundant specimens in a sample show morphologic gradations that lead us to conclude some form species are better referred to a single species. Many form species are often recognized in single samples making it difficult to stably identify species and a disadvantage to meeting requirements for high-resolution conodont biostratigraphy. The second approach was first mentioned in 1979 to identify ‘neogondolellids’ because the taxa show considerable morphologic variability. “Sample-populations” were formally adopted in 2004 for Clarkina to define the base Changhsingian, resulting in the stable definition, recognition and correlation of C. wangi. Four key points should be emphasized: 1) the method recognizes the entire sample population, including representatives of ontogenetic stages from juvenile to gerontic; 2) intraspecific variations in the shape of the segminiplanate element within a sample population are expected; 3) variation in platform shape of the same growth stage, and variations throughout ontogeny are important in a sample; 4) more than one population may be present in a sample. Yuan et al. (2014, 2017) used this approach to revise the Lopingian Clarkina taxonomy and succession of South China.

Yuan, D.X., Shen, S.Z., Henderson, C.M., Chen, J., Zhang, H., Feng, H.Z., 2014. Revised conodont-based integrated high-resolution timescale for the Changhsingian Stage and end-Permian extinction interval at the Meishan sections, South China. Lithos, 204: 220-245.

Yuan, D.X., Shen, S.Z., Henderson, C.M., 2017. Revised Wuchiapingian conodont taxonomy and succession of South China. Journal of Paleontology, 91: in press.