JOINTED legs.An arthropod is an invertebrate animal having an exoskeleton, a SEGMENTED body, and PAIRED jointed appendages.Arthropods form the phylum Euarthropoda, which includes insects, ARACHNIDS, MYRIAPODS, and crustaceans.The term Arthropoda as originally proposed refers to a proposed grouping of Euarthropods and the phylum Onychophora.The important characteristics of Arthropoda include:They possess an exoskeleton.They have jointed appendages.Their body is segmented.They are bilaterally symmetrical.They possess an open circulatory system.