Around 1867, along the shale cliffs on the lakeshore of Sheffield Lake, Jay Terrell found fossils of a “terrible fish” later named in his honor as Dinichthys terrelli. This animal, now known as Dunkleosteus terrelli, was a massive arthrodire, an extinct joint-necked, armor-plated fish, that lived in the Devonian sea, which covered much of eastern North America some 354-364 million years ago. Armed with an incredible set of shearing jaws, Dunkleosteus was clearly the top marine predator in the Devonian Period, the “Age of Fishes.”