''Ceraurus'' is a genus of cheirurid trilobite of the middle and, much more rarely, the upper

Ordovician The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era, and the second of twelve periods of the Phanerozoic Eon (geology), Eon. The Ordovician spans 41.6 million years f ...

. They are commonly found in strata of the lower

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region. These trilobites have eleven thoracic segments, a very small

pygidium The pygidium (: 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 compos ...

and long genal and pygidial spines. ''Ceraurus'' is quite common in the Ordovician of upstate

New York New York most commonly refers to: * New York (state), a state in the northeastern United States * New York City, the most populous city in the United States, located in the state of New York New York may also refer to: Places United Kingdom * ...

, south-central and south-eastern

Ontario Ontario is the southernmost Provinces and territories of Canada, province of Canada. Located in Central Canada, Ontario is the Population of Canada by province and territory, country's most populous province. As of the 2021 Canadian census, it ...

, and the

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in Quebec, as well as in the

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. It and similar genera range in size from less than quarter an inch to well over five inches. Similar genera of trilobites occur in the Ordovician outcrops of the

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, near St. Petersburg, Russia. The taxonomy of the genus is problematic, as the many variations of eye placement, decoration patterns of pustules, and spine length call the genus' defining characteristics into question. ''Ceraurus'' may, in fact, be at least four genera: ''Ceraurus''

sensu stricto ''Sensu'' is a Latin word meaning "in the sense of". It is used in a number of fields including biology, geology, linguistics, semiotics, and law. Commonly it refers to how strictly or loosely an expression is used in describing any particular c ...

, and the genera, ''Gabriceraurus'', ''Bufoceraurus'' and ''Leviceraurus''.

References

* Ludvigsen, Rolf, Fossils of Ontario: Part I: The Trilobites. Toronto:

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, 198

Cheiruridae Phacopida genera Extinct animals of North America Ordovician trilobites of North America Middle Ordovician first appearances Late Ordovician extinctions Bromide Formation Paleozoic life of Ontario Verulam Formation Paleozoic life of British Columbia Paleozoic life of the Northwest Territories Paleozoic life of Nunavut Paleozoic life of Quebec {{phacopida-stub