Crustaceans of the oceans

These go back to the Cambrian five hundred million years ago. The oceans in which they arose would appear like alien worlds teeming with oddities. Time to try a million variations, many varieties of trilobite, many varieties of shrimp, many varieties of crab, many kinds of eyes, arms, legs, mouths, feelers, bristles, many shapes and sizes, herbivores, detritivores, carnivores, insectivores, omnivores.