fragment of the stegocephalian skull in triassic period on white background.

nautiloids fossils rock isolated white background ordovician period group marine cephalopods mollusca originated fusulinid permian magnifying glass extinct foraminiferans single-celled organisms modern amoebas complex shells preserved waagenophyllum coral remains plants animals bodies buried sediments sand mud ancient seas lakes rivers brachiopods leptodus crinoid carboniferous fragment stegocephalian skull triassic background