Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2020 Jan 16;10(1):14.
doi: 10.1038/s41598-019-56010-z.

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

Andrew J Wendruff  1 , Loren E Babcock  2 , Christian S Wirkner  3 , Joanne Kluessendorf  4 , Donald G Mikulic  4
Affiliations

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

Andrew J Wendruff et al. Sci Rep. .

Erratum in

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.

PubMed Disclaimer

Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
Parioscorpio venator gen. et sp. nov., Brandon Bridge Formation (Silurian), Wisconsin, USA. (a) Holotype, UWGM 2162, photographed under low-angle lighting and revealing internal anatomy; (b) interpretive drawing of holotype; (c) Paratype, UWGM 2163, photographed under low-angle lighting; (d) interpretive drawing of paratype. Abbreviations: cx, coxa; fe, femur; fr, free finger; fx, fixed finger; gt, gut; le, lateral eye; me, median eyes; mt, metasomal segment; pa, patella; pc, pericardium; pfm, pedipalp femur; pm, pedipalp manus; pm.c, pedipalp manus carina; ppt, pedipalp patella; pr, pedipalp ramus; ps, pulmo-pericardial sinus; ptr, pedipalp trochanter; pv, poison vesicle; st, sternum; stn, sternite; tr, trochanter; wl, walking leg. Scale bar equals 5 mm.
Figure 2
Figure 2
Medial structures associated with the pulmonary-cardiovascular system in Silurian (a) and Holocene (b,c) scorpions. (a) Parioscorpio venator gen. et sp. nov., holotype, detail of medial region showing pulmo-cardiovascular structures; (b) SEM of Centruroides exilicauda, corrosion cast of pericardium and associated pulmo-pericardial sinuses; (c) Hadogenes troglodytes, male, dorsal surface, showing medial structures externally reflecting the position of the internal pericardium (compare with B). Abbreviations: bl, book lungs; pc, pericardium; ps, pulmo-pericardial sinus. Scale bars equal 1 mm for (a,b); scale bar equals 1 cm for (c).
Figure 3
Figure 3
Reconstruction of Parioscorpio venator gen. et sp. nov. Structures outlined in grey are inferred based on Proscorpius osborni. Structures highlighted with grey infilling are the preserved elements of the pulmonary-cardiovascular system.
Figure 4
Figure 4
Hypothesis of relationship based on character transformation (number of sternites) among some of the more completely known Paleozoic scorpions, with geologic time scale at left. One important trend in the evolution of early scorpions is a reduction in the number of sternites. P. venator shows the most primitive condition known, seven sternites. There was progressive reduction to six and eventually five sternites.
See this image and copyright information in PMC

References

    1. Dunlop, J. A., Scholtz, G. & Selden, P. A. Water-to-land transitions in Arthropod Biology and Evolution. (eds. Minelli, A., Boxshall, G. & Fusco, G. 417–439 (Springer, 2013).
    1. Dunlop JA, Webster M. Fossil evidence, terrestrialization and arachnid phylogeny. J. Arachn. 1999;27:86–93.
    1. Selden, P. A. & Dunlop, J. A. Fossil taxa and relationships of chelicerates in Arthropod Fossils and Phylogeny. (ed, Edgecombe, G. D.) 303–332 (Columbia University Press, 1998).
    1. Anderson LI, Clarkson ENK, Steward SE, Mitchell D. An upper Llandovery Konservat-Lagerstätte in a depositional context: the Pentland Hills Eurypterid Bed, Midlothian. Scot. J. Geol. 2007;43:41–50. doi: 10.1144/sjg43010041. - DOI
    1. Jeram AJ. Phylogeny, classification and evolution of Silurian and Devonian scorpions. Proc. 17th Eur. Colloq. Arachn. Edinb. 1998;1997:17–31.

Publication types