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A non-marine horseshoe crab from the Middle Triassic (Anisian)

The ~35 mm long, ~245 million-year-old horseshoe crab from this study. Source: Klompmaker et al. (2023).
The ~35 mm long, ~245 million-year-old horseshoe crab from this study. Source: Klompmaker et al. (2023).

Horseshoe crabs (Xiphosura) have a long evolutionary history starting in the Ordovician, but the number of species is relatively low. None of them have been reported from Alabama and many other places on Earth. We report on the first Triassic horseshoe crab from the Netherlands identifiable to the species level, a specimen of the limulid Limulitella bronnii. We provide the first diagnosis for this species and refigure the holotype. The new specimen was found in the Middle Triassic (Anisian) Muschelkalk sediments of the Vossenveld Formation, in the Illyrian part of the stratigraphic profile of the Winterswijk quarry complex. The Winterswijk specimen represents the youngest occurrence of L. bronnii. The inferred non-marine habitat of this horseshoe crab species elsewhere in conjunction with occurrences of plant and insect remains within the same layer at Winterswijk suggest the specimen herein most probably did not live in marine conditions either. This species has previously been found in non-marine sediments in France and Germany, expanding its geographic range northward. Several faunal elements from Winterswijk including L. bronnii show resemblance to the roughly co-eval non-marine components of the Anisian Grès à Voltzia Formation in NE France, suggesting a paleobiogeographic connection between these regions in Western Europe.

Klompmaker, A.A., Van Eldijk, T.J., Winkelhorst, H., and Reumer, J.W.F., 2023. A non-marine horseshoe crab from the Middle Triassic (Anisian) of the Netherlands. Netherlands Journal of Geosciences, 102, e1.