''Cnemidopyge'' is a genus of

trilobite Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the At ...

s that lived during the

Ordovician The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start ...

. Like all Raphiophorids it is blind, with a

cephalon Cephalon, Inc. was an American biopharmaceutical company co-founded in 1987 by pharmacologist Frank Baldino, Jr., neuroscientist Michael Lewis, and organic chemist James C. Kauer—all three former scientists with the DuPont Company. Baldino s ...

that is subtriangular to subsemicircular, carrying genal spines and a forward directed rapier-like spine on the central raised area (or

glabella The glabella, in humans, is the area of skin between the eyebrows and above the nose. The term also refers to the underlying bone that is slightly depressed, and joins the two brow ridges. It is a cephalometric landmark that is just superior to ...

), with the front of the glabella inflated and the natural fracture lines (or sutures) of the cephalon coinciding with its margin. It may be easily distinguished from other raphiophorids by the rectangular

thorax The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the cre ...

with 6 segments, where other genera have a different number of segments and segments change in width over the length of the thorax. Uniquely in this genus, the inner pleural region of the frontal segment is enlarged.Whittington, H. B. et al. (1997) Treatise on Invertebrate Paleontology. Part O, Revised, Volume 1 – Trilobita – Introduction, Order Agnostida, Order Redlichiida. Also the axis (or rhachis) and pleural fields of the

pygidium The pygidium (plural pygidia) is the posterior body part or shield of crustaceans and some other arthropods, such as insects and the extinct trilobites. In groups other than insects, it contains the anus and, in females, the ovipositor. It is compo ...

are strongly segmented.

References

Raphiophoridae Asaphida genera Ordovician trilobites of Europe Silurian trilobites Fossils of Great Britain Paleozoic life of the Northwest Territories Paleozoic life of Yukon {{Asaphida-stub