a sheet of peltasperm pteridosperm from the deposits of the kungursky tier of the lower permian of the urals

limestone ancient flora background closeup detail evolution exoskeleton extinct extinction find formation fossil fossilized geologic geological geology macro marine natural paleontology period russia sea specimen white leaf fern stone rarity paleontologist science hobby footprint fingerprint biology mineral old past pecopteris permian petrifaction petrification petrify plant ploetz prehistoric pumosa rock