THE FIRST POST-CAMBRIAN MARRELLOMORPH ARTHROPOD FROM NORTH AMERICA

A rare Silurian marrellomorph arthropod is recognized from the Waukesha Biota of Wisconsin, based on approximately ten specimens. Specimens exhibit a range of completeness, some including the cephalic and trunk regions, and others including only the cephalic region. Appendages are rare; however, one specimen includes a preserved cross-section of a pair of cephalic appendages with prominent gnathobases. Partial ?second antennae are present on at least two specimens. Ventrally and dorsally preserved specimens exist, including dorsal details of the cephalic shield, and a preserved hypostome on at least one specimen. Some detail of the anterolateral, mediolateral, and posterolateral cephalic shield spines is present on most specimens. The cephalic shield spines are conspicuously plumose, suggesting a close affinity to Furca spp., particularly cf. Furca spp. from the Fezouata Biota of Morocco. Preliminary phylogenetic analyses support this hypothesis. Recognition of a Silurian marrellomorph is highly significant in that only one other Silurian marrellomorph species, Xylokorys chledophilia, has been documented. Additionally, none of the rare post-Cambrian marrellomorphs has been documented from North America, but are known from Ordovician–Devonian Konservat-Lagerstätten of Europe and North Africa.