N. Robin,corresponding author1 P. Gueriau,2 J. Luque,3 D. Jarvis,1 A. C. Daley,2 and R. Vonk4,5


1School of Biological, Earth and Environmental Sciences, University College Cork, Distillery Fields, North Mall, Cork T23N73K, Ireland
2Institute of Earth Sciences, University of Lausanne, Géopolis, 1015 Lausanne, Switzerland
3Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA
4Department of Taxonomy and Systematics, Naturalis Biodiversity Center, 9517, 2300 RA Leiden, The Netherlands
5Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, 94240, 1090 GE Amsterdam, The Netherlands


Cell Biology


Peracarida (e.g. woodlice and side-swimmers) are, together with their sister-group Eucarida (e.g. krill and decapods), the most speciose group of modern crustaceans, suggested to have appeared as early as the Ordovician. While eucarids' incursion onto land consists of mainly freshwater and littoral grounds, some peracarids have evolved fully terrestrial ground-crawling ecologies, inhabiting even our gardens in temperate regions (e.g. pillbugs and sowbugs). Their fossil record extends back to the Carboniferous and consists mainly of marine occurrences. Here, we provide a complete re-analysis of a fossil arthropod—Oxyuropoda—reported in 1908 from the Late Devonian floodplains of Ireland, and left with unresolved systematic affinities despite a century of attempts at identification. Known from a single specimen preserved in two dimensions, we analysed its anatomy using digital microscopy and multispectral macroimaging to enhance the contrast of morphological structures. The new anatomical characters and completeness of Oxyuropoda, together with a phylogenetic analysis with representatives of all major Eumalacostraca groups, indicate that Oxyuropoda is a crown peracarid, part of a clade including amphipods and isopods. As such, Oxyuropoda is the oldest known species Peracarida, and provides evidence that derived peracarids had an incursion into freshwater and terrestrial environments as early as the Famennian, more than 360 Ma.



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Biol Lett.

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Ireland, Switzerland, USA