At left is Pterygotus, an ancient five-foot-long eurypterid predator that hunted trilobites and fish, one of the largest arthropods that ever lived. Fossilized specimens were found in exposed bedrock in a ditch alongside Beverly Drive in Fairmount Hills, probably during the laying out of the streets for the subdivision in the 1930s. (Similar fossils were found further west around Mansfield Drive.) Below is a size comparison of Pterygotus — also known as the sea scorpion — with humans and other prehistoric arthropods.
[Source: Journal of Paleontology Vol. 35, Society of Economic Paleontologists and Mineralogists, 1961, p.64.]