Lunataspis

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Lunataspis
Temporal range: 455–445 Ma Latest Sandbian to Earliest Hirnantian
Reconstruction of Lunataspis aurora (bottom left) and Lunataspis borealis (top right)
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Chelicerata
Order: Xiphosura
Genus: †Lunataspis
Rudkin, Young & Nowlan, 2008
Type species
†Lunataspis aurora
Rudkin, Young & Nowlan, 2008
Species
  • †L. aurora
    Rudkin, Young & Nowlan, 2008
  • †L. borealis
    Lamsdell et. al., 2022
  • †L. gundersoni
    Lamsdell et. al., 2025

Lunataspis is the oldest known xiphosuran, with three known species all dating from the late Ordovician (latest Sandbian for L. borealis, Katian for L. gundersoni, earliest Hirnantian for L. aurora).

Discovery and species

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Holotype of Lunataspis aurora
Holotype of Lunataspis borealis

The type species, L. aurora, was described from remains found in the Konservat-Lagerstätten deposits of the Stony Mountain Formation, central Manitoba by David Rudkin, Graham Young and Godfrey Nolan, from fossils found in northern Manitoba, Canada in 2005. [1][2] The specific name aurora is Latin for 'dawn' and is also eponymous with the mythological Roman goddess.[1] The deposit dates from the Late Ordovician, earliest Hirnantian c. 445 million years ago.

Size comparison of the three Lunataspis species: L.borealis on the left, L. aurora in the middle, and L. gundersoni on the right.

A second species, L. borealis, was described in 2022 based on three specimens, including an adult (ROM IP 64616) and two juveniles or subadults (ROM IP 64617 and ROM IP 64618). All specimens were found in the upper member of the Gull River Formation in Kingston, Ontario, dating from the latest Sandbian, late Ordovician, c. 454 million years ago.[3] This site was a warm-water platform shelf at the time near the paleo-equator.

A third species, L. gundersoni was described from two specimens found in the Big Hill Formation, which was likely a shallow lagoonal site connected to the ocean. Uniquely, this species has an elongated shovel-like prosoma with recurved posterior spines, as opposed to the more conventional form of the others. Alongside this, the holotype specimen also preserves a U-shaped structure interpreted as the ovaries, with pale spheres preserved within interpreted as eggs. This further suggests that this L. gundersoni specimen was an adult.[4]

See also

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References

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  1. ^ a b David M. Rudkin, Graham A. Young & Godfrey S. Nowlan (2008). "The oldest horseshoe crab: a new xiphosurid from Late Ordovician Konservat-Lagerstätten deposits, Manitoba, Canada". Palaeontology. 51 (1): 1–9. doi:10.1111/j.1475-4983.2007.00746.x.
  2. ^ Dunlop, J.A.; Penney, D.; Jekel, D. (2015). "A summary list of fossil spiders and their relatives" (PDF). World Spider Catalog. Bern, CH. Natural History Museum Bern. Archived (PDF) from the original on 2023-12-16.
  3. ^ Lamsdell, James C.; Isotalo, Phillip A.; Rudkin, David M.; Martin, Markus J. (October 2022). "A new species of the Ordovician horseshoe crab Lunataspis". Geological Magazine: 1–5. doi:10.1017/S0016756822000875. ISSN 0016-7568.
  4. ^ Lamsdell, James C.; Falk, Amanda R.; Hegna, Thomas A.; Meyer, Ronald C. (29 May 2025). "Exceptionally preserved ovaries in an ancient horseshoe crab". Geology. doi:10.1130/G53317.1.


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