21151 - Premium Grade Soft Bodied Xiphosurid (Horseshoe Crab Ancestor) Lower Ordovician Palaeonotopterus The texture is porphyritic

The texture is porphyritic

mean value δ18O=3

Calymenidae

Phalangocephalus

Barbosa et al

21151 - Premium Grade Soft Bodied Xiphosurid (Horseshoe Crab Ancestor) Lower Ordovician Palaeonotopterus The texture is porphyriticXiphosurans 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