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 complete 2-5/8" long example of Asaphus cornutus. This taxon derives its species name cornutus from the Latin for horned, referring to the eyestalks, which the animal could extend and retract, seen here fully extended. Specimen was found near the Wochow River in the St. Petersburg region of Russia and dates to the Ordovician Period (505 to 438 million years old). Seldom found w/extended eyestalks, this specimen was excavated separate from the eyestalks and later had them reattached as is the norm in paleontology. Makes for a great display.