Middle Furongian (late Cambrian) polymerid trilobites from the upper part of the Sesong Formation, Taebaeksan Basin, Korea

The upper part of the Sesong Formation of the Taebaek Group, Taebaeksan Basin, Korea, is known to contain the Kaolishania Zone which can be equated to the Kaolishania Zone of North China. Silicified trilobite sclerites were recovered from six horizons of the upper part of the Sesong Formation at the Sagundari section, which include a total of thirteen polymerid species: i.e., Shirakiella elongata Kobayashi, 1935, Shirakiella sp. 1, Taishania? sp. 1, Acanthometopus sp. 1, Pagodia sp. cf. P. spina Qian, 1994, Kaolishania granulosa Kobayashi, 1933, Gumunsoia triangularis gen. et sp. nov., Gumunsoia sp. 1, kaolishaniid genus and species indeterminate 1, Elaphraella? taebaeksanensis Park and Choi, 2012, Elaphraella microforma Lu and Qian, 1983, Elaphraella nodus (Qian, 1994), and Lingyuanaspis sp. The occurrence of Kaolishania suggests that the studied interval may be part of the Kaolishania Zone. However, Kaolishania occurs only from the lowermost horizon, and the full stratigraphic range of Kaolishania is unknown at present. Accordingly, the studied interval is provisionally called the Kaolishania fauna. The uppermost interval of this Kaolishania fauna produces Acanthometopus sp. 1, and thus can be correlated with the Acanthometopus Zone in Northeast China, which is underlain by the Kaolishania Zone.