Shrimp is the only crustacean (Arthropod subphylum Crustacea) in this group, while coral, sea anemones, and jellyfish are all cnidarians (phylum Cnidaria). The distinction is fundamental - shrimp have segmented bodies, jointed appendages, and a chitinous exoskeleton, unlike the other three which are soft-bodied radial organisms. This makes shrimp the clear odd one out.