Nautiloidea is the oldest subclass of cephalopods. They originated in the Paleozoic era in the Cambrian period. The earliest Nautiloid fossils (which come from China) demonstrate that they were a very diverse subclass of animals. Many of these early species died out, but one family Ellesmeroceratidae made past this initial hurdle and into the subsequent Ordovician period. All the other cephalopods from this period onward are descendants of the Ellemeroceratidaes.
rhamphotheca: End-Permian extinction happened in 60,000 years—much faster than earlier estimates, MIT study says The largest mass extinction in the history of animal life occurred some 252 million years ago, wiping out more than 96 percent of marine species and 70 percent of life on land—including the largest insects known to have inhabited the Earth.
A unique rock formation in the Atlas Mountains of Morroco contains thousands of specimens of perfectly preserved trilobites. After the rocks are collected highly skilled artisans use dental drills to cut away the matrix leaving these astonishing fossils.