Trilobites are a well-known fossil group of extinct marine arthropods, one of the earliest known groups of arthropods. They first appeared in the fossil record in the Early Cambrian Period (526 million years ago), and flourished throughout the lower Paleozoic Era before beginning a drawn-out decline to extinction when, during the Devonian Period, almost all trilobite orders died out before finally disappearing in the mass extinction at the end of the Permian Period, about 250 million years ago. Trilobites were among the most successful of all life forms, roaming the oceans for over 270 million years. Offered here are two complete examples of Novina convexa, measuring 2.25" and 2.5" long. These fossils date to the Ordovician Period 485.4 to 443.4 million years ago. The black exoskeleton shells of the trilobites contrast beautifully w/the 4.25x4.75x1.25" deep plate of stone it was fossilized in. Nice natural showcase from the Hunan Province of China. Exc.