When a Seven-Foot-Long Arthropod Swam the Seas

In the Ordovician period, some 443–485 million years ago, life was different. Peter Van Roy, co-author of a paper published this week in the journal Nature, describes a fossil found in Morocco dating back to that time—and it’s one of the largest arthropods ever discovered. A filter-feeder related to modern insects and crustaceans, the creature grew to more than six-and-a-half feet long. Aegirocassis benmoulae, as the animal is called, could help researchers better understand the evolution of arthropods’ body structures.