Isotelus is a genus of asaphid trilobites from the middle and upper Ordovician period, fairly common in the Northeastern United States, northwest Manitoba, southwestern Quebec and southeastern Ontario. 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, Manitoba, is the largest complete trilobite ever found. Discovered by Dave Rudkin (Royal Ontario Museum), 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) 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 Ohio, where Isotelus maximus is the state fossil. References 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