ISLAND INSTITUTE • January 13, 2021
Horseshoe crabs are among the most ancient of still-living beings. The earliest horseshoe crab fossil is from about 445 million years ago, which means they scuttled across the floors of Earth’s silent seas roughly 345 million years before any flower blossomed. They are the closest living relatives of the trilobites, who flourished during the first evolutionary explosion of multi-celled animals about 530 million years ago. And still living today as Limulus polyphemus, the Atlantic horseshoe crab, from Maine down the East Coast and the Gulf of Mexico to the Yucatan Peninsula, and as three other species in the Asian Pacific.