The oldest described eurypterid: a giant Middle Ordovician (Darriwilian) megalograptid from the Winneshiek Lagerstätte of Iowa

BMC Evolutionary Biology
James C LamsdellRobert M McKay

Abstract

Eurypterids are a diverse group of chelicerates known from ~250 species with a sparse Ordovician record currently comprising 11 species; the oldest fully documented example is from the Sandbian of Avalonia. The Middle Ordovician (Darriwilian) fauna of the Winneshiek Lagerstätte includes a new eurypterid species represented by more than 150 specimens, including some juveniles, preserved as carbonaceous cuticular remains. This taxon represents the oldest described eurypterid, extending the documented range of the group back some 9 million years. The new eurypterid species is described as Pentecopterus decorahensis gen. et sp. nov.. Phylogenetic analysis places Pentecopterus at the base of the Megalograptidae, united with the two genera previously assigned to this family by the shared possession of two or more pairs of spines per podomere on prosomal appendage IV, a reduction of all spines except the pair on the penultimate podomere of appendage V, and an ornamentation of guttalate scales, including angular scales along the posterior margin of the dorsal tergites and in longitudinal rows along the tergites. The morphology of Pentecopterus reveals that the Megalograptidae are representatives of the derived carcinosomatoid clade and...Continue Reading

References

Jul 28, 1999·Chemistry & Biology·S J StachelD L Van Vranken
Aug 24, 2012·Development Genes and Evolution·Carolin HaugJoachim T Haug
Jul 26, 2013·Proceedings of the National Academy of Sciences of the United States of America·Martin HughesMatthew Albion Wills
Jul 31, 2013·Die Naturwissenschaften·James C LamsdellPaul A Selden

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Citations

Jun 1, 2016·Arthropod Structure & Development·Jason A Dunlop, James C Lamsdell
Aug 4, 2020·Royal Society Open Science·Stephen PatesLucy A Muir

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