Crustaceans include turtles, crocodiles, armadillos and pangolins. All kinds of crustaceans of beetles (COLEOPTERA insects) have a chitin shell outside their bodies, which is called crustaceans. Crustaceans are a class of arthropods. Arthropods are the largest class in the animal kingdom, ranking first in both species and individuals. There are at least 65,438+000 species of arthropods in the world.