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 early animals, roaming the oceans for over 270 million years. Offered here is a 6.25x7x.75" thick plate containing the fossilized remains of three complete trilobites as well partial fossils for three other specimens. The two larger specimens (Coronocephalus rex) have been fossilized one on top of the other, as if mating. Top trilobite measures 2-7/8" long while both together measure 5" long. The smaller specimen (Yuepingia niobiformis) measures 1.5" long. This grouping dates to the Silurian Period (443.4 to 419.2 million years ago). The black exoskeleton shells of the trilobites contrast nicely w/the grey stone it was fossilized in. Nice natural showcase from the Hunan Province of China.