Fine Utah Ordovician Graptolite Pair

Description: This is a fine pair of graptolites known as Phyllograptus archaios. Graptolites are colonial animals belonging to the hemichordates. The term originates from the patronymic genus Graptolithus. The graptolites have a cosmopolitan distribution, and so serve as index fossils in many locations. The Graptoloidea were pelagic, drifting with the currents, and were the most important members of the plankton before dying out in the early Devonian. This genus draws its name from its leaf-like shape. Coming from the Fillmore Formation in Utah, the animal was part of the great radiation of the lower Ordovician, sometimes called the Ordovician Explosion.