Ogygopsis is a genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of trilobite

Trilobite

Trilobites are a well-known fossil group of extinct marine arthropods that form the class Trilobita. The first appearance of trilobites in the fossil record defines the base of the Atdabanian stage of the Early Cambrian period , and they flourished throughout the lower Paleozoic era before...

 from the Cambrian

Cambrian

The Cambrian is the first geological period of the Paleozoic Era, lasting from Mya ; it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's...

 of Antarctica and North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

, specifically the Burgess Shale

Burgess Shale

The Burgess Shale Formation, located in the Canadian Rockies of British Columbia, is one of the world's most celebrated fossil fields, and the best of its kind. It is famous for the exceptional preservation of the soft parts of its fossils...

. It is the most common fossil

Fossil

Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

 in the Mt. Stephen fossil beds there, but rare in other Cambrian faunas. Its major characteristics are a prominent glabella

Glabella

The glabella, in humans, is the space between the eyebrows and above the nose. It is slightly elevated, and joins the two superciliary ridges.-Etymology:The term is derived from the Latin glabellus, meaning smooth, as this area is usually hairless....

 with eye ridges, lack of pleural spines, a large spineless pygidium

Pygidium

The pygidium is the posterior body part or shield of crustaceans and some other arthropods, such as insects and the extinct trilobites. It contains the anus and, in females, the ovipositor...

 about as long as the thorax

Thorax

The thorax is a division of an animal's body that lies between the head and the abdomen.-In tetrapods:...

 or cephalon

Cephalon

Cephalon, Inc. is a U.S. biopharmaceutical company co-founded in 1987 by Dr. Frank Baldino, Jr., a pharmacologist and former scientist with the DuPont Company, who served as the company's chairman and chief executive officer until his death in December 2010...

, and its length: up to 12 cm.

Sources

• Fossils (Smithsonian Handbooks) by David Ward (Page 64)
• Ogygopsis in the Paleobiology Database
  Paleobiology Database
  ' is an online resource for information on the distribution and classification of fossil animals, plants, and microorganisms.-History:The Paleobiology Database was founded in 2000. It has been funded by the National Science Foundation and the Australian Research Council...