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Early Devonian pterygotid eurypterids from Yunnan Province, China

Published online by Cambridge University Press:  24 September 2025

Maxwell Wang Open the ORCID record for Maxwell Wang [Opens in a new window] ,
Simon Braddy ,
Victoria Tang Open the ORCID record for Victoria Tang [Opens in a new window]  and
Zhiheng Ma Open the ORCID record for Zhiheng Ma [Opens in a new window]
Maxwell Wang
Affiliation:
Kunming General Survey of Natural Resources Center, https://ror.org/04wtq2305China Geological Survey, Kunming, Yunnan, China https://ror.org/02jx3x895Universiy College London, Gower Street, London WC1E 6BT, UK
Simon Braddy
Affiliation:
Manorbier, Pembrokeshire, UK
Victoria Tang
Affiliation:
Pudong New District, Shanghai, China
Zhiheng Ma*
Affiliation:
Kunming General Survey of Natural Resources Center, https://ror.org/04wtq2305China Geological Survey, Kunming, Yunnan, China School of Geoscience and Technology, Southwest Petroleum University, Chengdu, Sichuan, China
*
Corresponding author: Zhiheng Ma; Email: 1625194814@qq.com
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Abstract

Pterygotids were Paleozoic marine and marginal marine large apex predatory arthropods. However, their evolution remains poorly understood due to the scarcity of their fossils and the delicate nature of their exoskeletons. The well-studied Devonian Xiaxishancun Formation in Qujing City, Yunnan, China contains various Agnatha and three eurypterid species. Our study focuses on the eurypterid material assigned to Erettopterus qujingensis Ma et al., 2022 and Pterygotus wanggaii Ma et al., 2023. The two species were discovered from the same locality, both with individuals of different developmental stages (juveniles more common), suggesting that this area could represent a breeding site, in agreement with mass molt behavior and the occurrence of other pterygotids in shallow waters. Moreover, the coexistence of heavily armed Agnatha with Pterygotus wanggaii in the Xiaxishancun Formation, alongside their robust chelicerae, supports the hypothesis that some pterygotids were piscivorous. In addition, due to ambiguity of pterygotid cheliceral dentition nomenclature, we introduce a new framework to define the cheliceral denticle types of pterygotids based on their relative positions: TD, terminal denticle; MD, median denticle (including: MMD, modified MD, and OMD, ordinary MD); BD, basal denticle. A key diagnostic feature in the cheliceral denticles of E. qujingensis is established: movable finger ends in a curved TD, 3 MMD’s present, 9 OMDs between MMD1 and MMD2 (OMD4 and OMD8 slightly enlarged); fixed finger ends in an acute TD’, 3 MMD’s present (MMD’2 being the largest), 8 OMD’s between MMD’1 and MMD’2 (OMD’5 slightly enlarged), 15 OMD’s between MMD’2 and MMD’3 (OMD’1 and OMD’10-12 slightly enlarged). This cheliceral diagnosis distinguishes E. qujingensis from Pterygotus wanggaii by its distinct number of MMDs.

Keywords

EurypteridaPterygotidaePterygotusErettopteruscheliceraeYunnan

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Journal of Paleontology , First View , pp. 1 - 19
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© The Author(s), 2025. Published by Cambridge University Press on behalf of Paleontological Society

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Footnotes

Handling Editor: James Lamsdell

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