Emsian (Lower Devonian) conodonts from the Daliantang Formation at Daliantang, southeastern Yunnan, China

The lower/upper Emsian boundary witnessed prominent diversification of biostratigraphically important genera Polygnathus Hinde, Caudicriodus Bultynck, and Latericriodus Mu spacing diaeresis ller. In contrast, conodonts previously reported around this boundary from the South China Block were characterized by relatively low species or subspecies diversity, and only a few widely distributed and extensively studied zone-defining taxa were recorded. In this paper, conodonts from the Daliantang Formation at the Daliantang section (Guangnan, southeastern Yunnan), one of the representative sections of the transitional facies between the benthic Xiangzhou facies and the pelagic Nandan facies, are investigated. The conodont fauna shows a remarkably high species or subspecies diversity, with fourteen taxa that are assignable to the notoperbonus Zone and inversus Zone. Five polygnathid species are described: P. gronbergi Klapper and Jonson, P. inversus Klapper and Jonson, Polygnathus sp. B, P. luciae Marti acute accent nez-Pe acute accent rez and Valenzuela-Ri acute accent os, and P. mashkovae Bardashev. The latter two are reported for the first time from the South China Block. Additionally, three icriodontid taxa are also described, of which L. guangnanensis n. sp. is characterized by distinctly chevron-shaped transverse rows in the anterior part and a well-developed process branching off to the outer side. The new conodont record increases our understanding of the diversification and faunal composition around the lower/upper Emsian boundary in the South China Block. It contributes to the regional and inter-regional biostratigraphical correlation between shallower- and deeper-water facies and also furnishes important South China material for future discussion and deliberation on the position of the lower/upper Emsian boundary. (c) 2020 Elsevier B.V. and Nanjing Institute of Geology and Palaeontology, CAS. All rights reserved.

Automated summary

The study found a high diversity of conodonts around the lower/upper Emsian boundary in the South China Block, including newly discovered species and taxa recorded for the first time in the region. This new discovery contributes to a better understanding of the faunal composition and regional biostratigraphical correlation during this period in the South China Block.