Trilobites are a well-known fossil group of extinct marine arthropods, one of the earliest known groups. They first appeared in the fossil record in the Early Cambrian Period (526 million years ago), flourishing 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 is a lot of four complete fossilized trilobites, including three examples of Metacanthina and one Phacops rana specimen. These fossils date to the Devonian Period (419.2–358.9 million years ago) and were unearthed in Morocco. The Metacanthina measure 2", 2.5" and 2-5/8" long and all are nicely preserved, w/fine details of the eyes visible on both larger specimens and partially visible on one eye of the smaller specimen. The Phacops measures 4" long. The most striking feature of the morphology of Phacops and its relatives is their eyes. These differed from the eyes of most trilobites in having comparatively few lenses spaced between deep sclera. The lenses themselves were very rounded instead of largely flat. The eyes were mounted on turret-like structures which could swivel, providing the animal w/an almost 360 degree field of view. This trilobite's eyes are remarkably well preserved, w/an amazing amount of detail visible. Tiny bumps are also visible on the trilobite's carapace. These trilobites are often found rolled up in a ball-like position, a defensive feature they used to protect themselves from predators, w/its hard exoskeleton on the outside acting like a shield. This specimen is fully stretched out, and wonderfully preserved. Nice grouping of trilobites in wonderful condition. From the Robert M. Overstreet Collection and comes with COA.