Trilobites of trinucleid, raphiophorid and cyclopygid associations from the Ordovician (Darriwilian – early Katian) of the west Balkhash region and Betpak‐Dala, Central Kazakhstan

Abstract

AbstractMiddle to Late Ordovician (late Darriwilian –early Katian) trilobites from trinucleid, raphiophorid and cyclopygid biofacies are for the first time documented from the West Balkhash and North Betpak‐Dala regions in south‐central Kazakhstan. Twenty taxa are described; six of them, that is, Miaopopsis sokyrensis sp. nov., Pricyclopyge keralensis sp. nov., Kongqiaoheia sarytumensis sp. nov., Shumardia karasaiensis sp. nov., Triarthrus akkermensis sp. nov. and Mynaralaspis perforata gen. et sp. nov. are new to science. Six taxa are reported in open nomenclature and two are not identified on a genus level. A new trinucleid Subfamily Nanshanaspinae is designated. Newly discovered faunas show strong links to contemporaneous faunas of Tarim and, to a lesser degree, to those of South China and the Australian sector of Gondwana. Based on results of cluster analysis (Dice similarity), trilobite associations of raphiophorid biofacies from the Chu‐Ili and Stepnyak terranes form a single first‐order cluster with little similarity to the trilobite associations characteristic of the nielid and illenid–cheirurid biofacies from the Stepnyak and Tarbagatai regions. Also, there is no distinct interaction between the pelagic Degamella–Pricyclopyge association and other trilobite faunas. The geographical distribution of raphiophorid and trinucleid trilobites described in this paper, including species of genera Malongullia?, Miaopopsis, Nanshanaspis and Kongqiaoheia, supports Ordovician palaeogeographical reconstructions showing the Kazakh terranes as part of a huge archipelago situated on both sides of the equator in proximity to the west coast of Gondwana and positioned a considerable distance from the Siberia continent and its associated terranes.