"Lost World: Wisconsin's Prehistoric Extinct Animals Revealed"

A recent study suggests that volcanic eruptions may have already threatened the existence of dinosaurs before the asteroid collision that killed them off. In Wisconsin, during the Cambrian period, giant jellyfish up to three feet wide roamed the waters. The state was also home to ancient coral reefs, trilobites, and a tentacled relative of octopi called the giant nautilus. The Conodont Panderodus, a fish with fangs, lived in Waukesha County during the Silurian era. Mammoths and mastodons, ancient relatives of elephants, roamed Wisconsin during the Ice Age and may have interacted with humans.