Rare Russian Ordovician Trilobite Ptychopyge limbata

Description: A well-inflated example of a scarce Asaphid, this is Ptychopyge limbata. The golden Calcite exoskeleton is complemented by the white limestone matrix, with the trilobite shown in a prone position. This is one of the older members of the ptychopyge genus. Coming from an inland sea during the lower to middle Ordovician, the Russian trilobites from near Saint Petersburg, Russia participated in the Great Ordovician Radiation, which saw marine animal diversity increase three-fold more than the Cambrian Explosion. The Russian asaphid trilobites are a particularly interesting example of descent with modification.