👉 'Amphicarpaea' is a term used in the field of natural history to refer to an ancient family of crustacean insects that were known from the late Eocene period (25.6–51 million years ago) and are now extinct. They were characterized by their long, curved shells, which resembled those of modern sea urchins. These crustaceans possessed a pair of legs on each segment, and were typically found in shallow waters or brackish habitats.