Isotelus rex, the biggest trilobite ever found, was discovered in northern Manitoba. It was over 70 cm long and it lived 445 million years ago, when much of North America was covered by shallow seas. The fossil represents a new species of the genus Isotelus, a group characterized by rounded features and a lack of protruding ornamentation. Most of the other Isotelus trilobites are much smaller than Isotelus rex, which is 30 cm longer than the largest trilobites previously discovered. The chart below, created by Sam Gon III, compares Isotelus rex with some of the other large trilobites, and a familiar object for scale reference.
Isotelus rex was one of the biggest arthropods that ever lived, with the same body length as Mike, the largest lobster ever recorded. Most of the other trilobites were between 3 and 10 cm long. Dr Graham Young said: "We have found a very unusual specimen that illustrates some of the diversity and weirdness of ancient life. A trilobite of this size really is an amazing discovery." Below is an artist's interperetation of how Isotelus Rex may have looked when alive.