Arthropoda (phylum)

The largest phylum in the animal kingdom; includes lobsters, crabs, spiders, insects, centipedes, and millipedes. Diverse in structure, lifestyle, and habitat, about 84 percent of the known species of animals are members of this phylum. Arthropds are characterized by the presence of a skeletal covering composed of chitin, a complex sugar, bound to protein. This nonliving exoskeleton is secreted by the underlying epidermis, similar to the skin of other animals. The body is usually segmented with jointed appendages, from which the name arthropod or "jointed feet" is derived.