21153 - Premium Grade Soft Bodied Xiphosurid (Horseshoe Crab Ancestor) Lower Ordovician Rare Furca shares the head shield

Furca shares the head shield morphology of marrellids

palaeobiogeographic distribution and phylogenetic position

Sepkoski 2002 and Thurmond 1969

falcoid ribs that spring in pairs from umbilical tubercles

21153 - Premium Grade Soft Bodied Xiphosurid (Horseshoe Crab Ancestor) Lower Ordovician Rare Furca shares the head shieldXiphosurans are an order of arthropods related to arachnids, or, according to one recent study, actually arachnids. They are sometimes called horseshoe crabs (a name applied more specifically to the only extant family, Limulidae). They first appeared in the Tremadocian (Lower Ordovician) from Fezouata Fm in South Morocco. Currently, there are only four living species. They are members of the order Xiphosura, which contains two suborders, Xiphosurida