437 million years ago, the Midwestern suburb now known as Waukesha County, Wisconsin, was a tropical coastline. It was teeming with trilobites, early scorpions, and other prehistoric creatures.

It was the Silurian period, an era that may have been the birthplace of the first known leech, which was much more of a lethal hunter than the parasitic bloodsucker it is known to be today.

Discovered in the limestone near Waukesha, a creature named Macromyzon siluricus, which means “large sucker from the Silurian,” was a cowbell-shaped sea creature with a segmented body.

It had a big ol’ suction cup on the portion of the body we would scientifically refer to as “the butt,” a feature still found on modern leeches. However, unlike modern vampiric leeches, Macromyzon lived in saltwater and ate larg

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