Isotelus

Isotelus is a genus of asaphid trilobite 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 worlds largest complete trilobite.

Isotelus rex
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 720 mm in length, 400 mm in maximum width (across the cephalon) and 70 mm in maximum height (at the posterior mid-point of the cephalon).

Large specimens have also been found in Ohio, 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)
 * glabella indicated by weakly raised smooth area near rear of head shield
 * thorax has 8 segments and slightly raised middle lobe (between the outer pleuae)
 * Time range upper Ordovician (500–480 mya)