21150 - Great Soft Bodied 2 Xiphosurids (Horseshoe Crab Ancestor) Lower Ordovician Phacodus It was initially assigned to

It was initially assigned to the family Trematochampsidae

without restorations

Ginglymostoma globidens

Sepkoski 2002 and Whittington 1956

Anetoceras multicostatum

21150 - Great Soft Bodied 2 Xiphosurids (Horseshoe Crab Ancestor) Lower Ordovician Phacodus It was initially assigned toXiphosurans 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