A Silurian ancestral scorpion with fossilised internal anatomy illustrating a pathway to arachnid terrestrialisation

An Author Correction to this article was published on 18 November 2020

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Abstract

Scorpions are among the first animals to have become fully terrestrialised. Their early fossil record is limited, and fundamental questions, including how and when they adapted to life on land, have been difficult to answer. Here we describe a new exceptionally preserved fossil scorpion from the Waukesha Biota (early Silurian, ca. 437.5–436.5 Ma) of Wisconsin, USA. This is the earliest scorpion yet reported, and it shows a combination of primitive marine chelicerate and derived arachnid characteristics. Elements of the circulatory, respiratory, and digestive systems are preserved, and they are essentially indistinguishable from those of present-day scorpions but share similarities with marine relatives. At this early point in arachnid evolution, physiological changes concomitant with the marine-to-terrestrial transition must have occurred but, remarkably, structural change in the circulatory or respiratory systems appear negligible. Whereas there is no unambiguous evidence that this early scorpion was terrestrial, this evidence suggests that ancestral scorpions were likely capable of forays onto land, a behavior similar to that of extant horseshoe crabs.

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  • 18 November 2020

    An amendment to this paper has been published and can be accessed via a link at the top of the paper.

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Acknowledgements

We thank C. Eaton for loan of specimens from the University of Wisconsin-Madison Geology Museum. S. Kiff provided the specimen of Hadogenes. Specimens were collected under National Science Foundation grant (DEB 92-01048) to D. G. Mikulic and J. Kluessendorf. The manuscript benefited from the reviews of two anonymous reviewers.

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Specimens were collected as part of a project directed by D.G.M. and J.K.A.J.W., L.E.B., D.G.M. and J.K. developed the project. A.J.W. and L.E.B. analysed specimens. A.J.W. photographed the fossil specimens and the Hadogenes troglodytes specimen. C.W. created and imaged the corrosion cast of Centruroides exilicauda. A.J.W. created the explanatory drawings and reconstruction. All authors reviewed and edited the final manuscript.

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Correspondence to Andrew J. Wendruff.

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Wendruff, A.J., Babcock, L.E., Wirkner, C.S. et al. A Silurian ancestral scorpion with fossilised internal anatomy illustrating a pathway to arachnid terrestrialisation. Sci Rep 10, 14 (2020). https://doi.org/10.1038/s41598-019-56010-z

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