''Isotelus'' is a genus of asaphid

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 ...

s from the middle and upper

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period, fairly common in the

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, northwest

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, southwestern

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and southeastern

Ontario Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central Ca ...

. One species, ''Isotelus rex,'' is currently the world's largest trilobite ever found as a complete fossil, and was probably exceeded in size only by '' Hungioides bohemicus,'' in which the specimens probably exceeding ''Isotelus rex'' in size are only known from partial remains.

Discovery and naming

A specimen of ''Isotelus rex'', from

Churchill Sir Winston Leonard Spencer Churchill (30 November 187424 January 1965) was a British statesman, soldier, and writer who served as Prime Minister of the United Kingdom twice, from 1940 to 1945 during the Second World War, and again from 1 ...

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, is the largest complete trilobite ever found. Discovered by Dave Rudkin (

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), Robert Elias (University of Manitoba), Graham Young (Manitoba Museum) and Edward Dobrzanske (Manitoba Museum) in 1999, it measures in length, in maximum width (across the

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 ...

) and in maximum height (at the posterior midpoint of the cephalon). A number of species have been described: *''I. aktchokensis'' Weber, 1948 *''I. bradleyi'' Amati, 2014 *''I. copenhagenensis'' Ross, Jr. & Shaw 1972 *''I. frognoensis'' Owen, 1981 *''I. gigas'' Dekay, 1824 *''I. harrisi'' Raymond, 1905 (synonym ''I. platymarginatus'' Raymond, 1910) *''I. iowensis'' Owen, 1852 *''I. kimmswickensis'' Bradley, 1930 *''I. maximus'' Locke, 1838 *''I. megistos'' Locke, 1842 *''I. parvirugosus'' Chatterton & Ludvigsen, 1976 *''I. skapaneidos'' Amati, 2014 *''I. susae'' Whitfield, 1882 *''I. violaensis'' Amati, 2014 *''I. walcotti'' Walcott, 1918 (synonym ''I. planus'' De Mott, 1963) Many specimens have also been found in

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, where ''Isotelus maximus'' is the

state fossil Most American states have made a state fossil designation, in many cases during the 1980s. It is common to designate one species in which fossilization has occurred, rather than a single specimen, or a category of fossils not limited to a single ...

References

{{Taxonbar, from=Q44087 Asaphida genera Bromide Formation Extinct animals of North America Ordovician trilobites Paleozoic life of Manitoba Paleozoic life of Nunavut Paleozoic life of Ontario Verulam Formation Paleozoic life of Quebec Paleozoic life of the Northwest Territories Symbols of Ohio