Step 3: Compare the traits of Arthropoda with the other phyla listed: Cnidaria, Annelida, and Mollusca. Cnidaria includes animals like jellyfish and corals, which lack segmentation, jointed appendages, and an exoskeleton. Annelida includes segmented worms, but they do not have jointed appendages or a chitinous exoskeleton. Mollusca includes animals like snails and clams, which have a shell but lack jointed appendages and segmentation.