The subphylum Crustacea have each of the appendages being biramous, meaning it contains 2 main branches. The crustaceans also have 2 or 3 body regions: cephalothorax and abdomen or head, thorax, and an abdomen. Unlike the subphylum Cheliceriformes, the Crustaceans have a mandible and 2 pairs of antennae.
The Isopods are the most diverse Crustaceans. They are mostly found in terrestrial, freshwater, and saltwater habitat. An example of this class would be the Sowbug.
Examples of this class would be the lobster and the crabs. They are mostly aquatic species.
These class of species are mostly found in marine, freshwater plankton community. AN example of this would be the copepod.