Isotelus is a genus of asaphid

Asaphida

Asaphida is a large, morphologically diverse order of trilobite found in strata dated from the Middle Cambrian to the Silurian. The order contains six superfamilies , but no suborders...

 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 middle and upper Ordovician

Ordovician

The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...

 period, fairly common in the Northeastern United States

Northeastern United States

The Northeastern United States is a region of the United States as defined by the United States Census Bureau.-Composition:The region comprises nine states: the New England states of Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island and Vermont; and the Mid-Atlantic states of New...

, northwest Manitoba

Manitoba

Manitoba is a Canadian prairie province with an area of . The province has over 110,000 lakes and has a largely continental climate because of its flat topography. Agriculture, mostly concentrated in the fertile southern and western parts of the province, is vital to the province's economy; other...

, southwestern Quebec

Quebec

Quebec or is a province in east-central Canada. It is the only Canadian province with a predominantly French-speaking population and the only one whose sole official language is French at the provincial level....

 and southeastern Ontario

Ontario

Ontario is a province of Canada, located in east-central Canada. It is Canada's most populous province and second largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa....

. One species, Isotelus rex, is currently the world's largest complete trilobite.

Isotelus rex

A specimen of Isotelus rex, from Churchill

Churchill, Manitoba

Churchill is a town on the shore of Hudson Bay in Manitoba, Canada. It is most famous for the many polar bears that move toward the shore from inland in the autumn, leading to the nickname "Polar Bear Capital of the World" that has helped its growing tourism industry.-History:A variety of nomadic...

, 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 720 millimetres (28 in) in length, 400 millimetres (16 in) in maximum width (across the cephalon) and 70 millimetres (3 in) in maximum height (at the posterior mid-point of the cephalon).

Large specimens have also been found in Ohio

Ohio

Ohio is a Midwestern state in the United States. The 34th largest state by area in the U.S.,it is the 7th‑most populous with over 11.5 million residents, containing several major American cities and seven metropolitan areas with populations of 500,000 or more.The state's capital is Columbus...

, where Isotelus maximus is the state fossil.

Physical description

• very similar to Homotelus
• “double” posterior
• head and tail shields are semi-circular and very similar in shape (isopygus)
• thorax has 8 segments and slightly raised middle lobe (between the outer pleurae)
• Time range middle and upper Ordovician (500–480 mya)