Isotelus

The largest known Isotelus specimen, dubbed Isotelus rex, was discovered in Manitoba, Canada, near the shores of Hudson Bay. Measuring over 28 inches (72 centimeters) in length, it ranks among the largest trilobites ever found. It lived during the Late Ordovician period, roughly 445 million years ago.

Isotelus is the official state fossil of Ohio, a designation made in 1985. Fossils of this giant trilobite are commonly found in the Ordovician-aged rocks and limestone deposits of the state. A particularly famous, nearly complete specimen was unearthed in Dayton, Ohio, in 1919.

While Isotelus rex reached massive sizes, an average Isotelus specimen was typically between 8 and 12 inches long. They possessed a smooth, oval-shaped exoskeleton, large compound eyes, and a distinctive trilobed body. Unlike many of their spiny relatives, they had a relatively smooth, sleek appearance.

Yes, paleontologists believe Isotelus was a benthic creature, meaning it crawled along the ocean floor. Its anatomy, including its strong legs and flat body shape, was well-suited for hunting small invertebrates in the mud. It thrived in the warm, shallow seas that covered much of North America during the Ordovician period.