Arthropod

Summary
Arthropods are creatures which sport hard exoskeletons on the outside, instead of the inside, of their bodies. Arthropods have been around for millions of years, back to the Cambrian period, when most living things were soft-bodied, mindless cells (like jellyfish) floating around in the sea. Anomalocaris was one of the first Arthropods, who quickly evolved into the likes of Brontoscorpio and Pterygotus. The golden age of the arthropods dawned during the Carboniferous, when they evolved to become huge, such as the 4-metre long millipede Arthropleura and the giant dragonfly Meganeura. Athropods still exist today, such as insects and arachnids, but they are small and past their glory days.