Article: The respiratory organs of eurypterids

Cuticle fragments from the upper Silurian (Pridoli Series) of south Shropshire, England, are described and interpreted as the respiratory organs of eurypterids. These fragments, combined with whole body evidence, suggest a dual respiratory system: lamellate book-gills, homologous with those of modern xiphosurans and arachnid book lungs, and an additional Kiemenplatten on the true sternite, the roof the branchial chamber. Kiemenplatten is used in preference to gill-tract, because it is a more 'neutral' term, without functional implications. Eurypterids may have been partially terrestrial: the Kiemenplatten is interpreted as an accessory aerial respiratory organ, most closely analogous to the branchial 'lungs' of certain terrestrial crabs. Cuticular projections from the Kiemenplatten are interpreted as having held a layer of water to keep the structure moist during excursions onto land. A new reconstruction of the eurypterid respiratory system is presented.