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Exceptionally preserved Cambrian loriciferans and the early animal invasion of the meiobenthos

Nature Ecology & Evolution volume 1, Article number: 0022 (2017) | Download Citation

Abstract

Microscopic animals that live among and between sediment grains (meiobenthic metazoans) are key constituents of modern aquatic ecosystems, but are effectively absent from the fossil record. We describe an assemblage of microscopic fossil loriciferans (Ecdysozoa, Loricifera) from the late Cambrian Deadwood Formation of western Canada. The fossils share a characteristic head structure and minute adult body size (~300 μm) with modern loriciferans, indicating the early evolution and subsequent conservation of an obligate, permanently meiobenthic lifestyle. The unsuspected fossilization potential of such small animals in marine mudstones offers a new search image for the earliest ecdysozoans and other animals, although the anatomical complexity of loriciferans points to their evolutionary miniaturization from a larger-bodied ancestor. The invasion of animals into ecospace that was previously monopolized by protists will have contributed considerably to the revolutionary geobiological feedbacks of the Proterozoic/Phanerozoic transition.

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Acknowledgements

We thank staff at the Geological Subsurface Laboratory, Regina, Saskatchewan, and M. Vélez, University of Regina, for help with core sampling. We thank geoLOGIC for generous access to subsurface data. This work was supported by Natural Environment Research Council Grant NE/H009914/1.

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Affiliations

  1. Department of Geology, University of Leicester, University Road, Leicester LE1 7RH, UK

    • Thomas H. P. Harvey
  2. Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK

    • Nicholas J. Butterfield

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Contributions

T.H.P.H. and N.J.B. designed and performed the research and wrote the paper.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Thomas H. P. Harvey.

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DOI

https://doi.org/10.1038/s41559-016-0022

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