Palynological recovery of small carbonaceous fossils (SCFs) indicates that the late Cambrian acritarch Goniomorpha Yin 1986 represents the teeth of a priapulid worm

Abstract

New palynological studies from the Xiaoyangqiao section (Jilin Province, north-east China), which has been selected as an Auxiliary Boundary Stratigraphic Section and Point (ASSP) for the base of the Ordovician, confirms the presence of Goniomorpha Yin 1986 in intervals ranging from the late Cambrian (Furongian) to the Early Ordovician (Tremadocian), and allow us to clarify its morphology and affinities. Despite being compared originally to vesicular microfossils with processes arising from one pole, Goniomorpha lacks an enclosed cavity, so it cannot be classified as an acritarch in the strict sense. Instead, we find that the specimens originally described as Goniomorpha are actually part of a wider spectrum of morphologies that are identifiable as the pharyngeal teeth of priapulid worms. The best-preserved specimens resolve the ‘processes’ as denticles arising from an arch on the margins of a cuticular pad, sometimes with an extending spur and polygonal microstructure. Closely equivalent forms have been reported from Cambrian assemblages of small carbonaceous fossils (SCFs) and in situ on Burgess Shale specimens of the priapulid Ottoia. The findings from the Xiaoyangqiao section extend the taphonomic range of Cambrian-type SCFs into the Ordovician, and provide the first evidence for priapulids from the Ordovician of northern China. More generally, our results demonstrate the reciprocal insights from palynological and SCF-type processing for identifying problematic microfossils.

Keywords:

• acritarchs
• microfossils
• Cambrian–Ordovician boundary
• SCFs
• worms
• China

Acknowledgements

We thank Dr Guanzhou Yan for the identification of conodont fossils and the division of biological zones. We also thank Dr Ben Slater and two anonymous reviewers for their detailed and constructive comments on the manuscript, as well as Jim Riding for editorial assistance.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China (NSFC) (Grant No. 42030510) and the Chinese Academy of Sciences (No. XDB26000000). This work is a contribution to IGCP projects 653 (The Onset of the Great Ordovician Biodiversification Event) and 735 (Rocks and the Rise of Ordovician Life – Rocks n’ ROL).

Notes on contributors

Longlong Shan

LONGLONG SHAN is a doctoral candidate at the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS). He graduated from Henan University in 2016, and received his Master’s degree from NIGPAS in 2019. He is currently at the CNRS, Université Lille, UMR 8198 – Evo-Eco-Paleo, France, for a joint training programme from 2021 to 2022, and mainly works on the stratigraphical, palaeoecological and palaeogeographical significance of late Cambrian to Early Ordovician palynomorphs from North China.

Thomas H.P. Harvey

THOMAS H. P. HARVEY is a lecturer in geoscience at the University of Leicester, UK. His research is focused on the Proterozoic–Phanerozoic transition, including the origins and early evolution of animals and their environments. He is particularly interested in reconstructing animal anatomy, phylogeny and ecology using exceptionally preserved macrofossils and SCFs.

Kui Yan

KUI YAN is an associate researcher at the Nanjing Institute of Geology and Palaeontology, China. He mainly works on the stratigraphical and palaeogeographical significance of the Early Palaeozoic microphytoplankton of China. Specifically, he specialises in the study of interactions between palaeoenvironment and microphytoplankton evolution during the Great Ordovician Radiation.

Jun Li

JUN LI is a research professor at the Nanjing Institute of Geology and Palaeontology, China. He visited the University of Sheffield, UK, during 1985, and the University of Lille 1, France, on numerous occasions between 2000 and 2017. He also visited Central Michigan University, USA, for three months in 2004. His research is focused on Ordovician and Silurian acritarchs.

Yuandong Zhang

YUANDONG ZHANG is a researcher and the Deputy Director of the State Key Laboratory of Palaeobiology and Stratigraphy (Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences), and the Secretary-General of the Palaeontological Society of China. He received his PhD on Ordovician graptolites from the Nanjing Institute of Geology and Palaeontology in 1993, and has been working on Lower Palaeozoic stratigraphy, graptolites and related organisms since the 1990s. Over the past two decades, he led several major research projects, sponsored by the National Natural Science Foundation and the Ministry of Science and Technology of China, and the Chinese Academy of Sciences, on the Ordovician radiations, marine gas shale in South China and the palaeogeographic reconstruction of South China at some specific times within the Palaeozoic. He was among the co-leaders of the IGCP653 project, which was on the ‘Onset of the GOBE’.

Thomas Servais

THOMAS SERVAIS is a Research Director at the French Centre of Scientific Research (CNRS). His research is focused on the biostratigraphy, palaeobiogeography and palaeoecology of Palaeozoic acritarchs. His current research is mostly dedicated to a better understanding of the Ordovician Plankton Revolution. He is currently Chairman of the Ordovician Subcommission of Stratigraphy.