21165 - Premium Grade Soft Bodied Xiphosurid (Horseshoe Crab Ancestor) Lower Ordovician KemKem_Sawfish Journal of Vertebrate Paleontology 30(5):1632-1636

Journal of Vertebrate Paleontology 30(5):1632-1636

Bell and Polcyn 2005

10-25 μm faceted prisms

Inside we can see fossilized and polished Orthoceras

Pyroxene crystals show complex zoning patterns

21165 - Premium Grade Soft Bodied Xiphosurid (Horseshoe Crab Ancestor) Lower Ordovician KemKem_Sawfish Journal of Vertebrate Paleontology 30(5):1632-1636Xiphosurans 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