Example is acorn worm. Individuals have jointed feet . Only extinct group of arthropods. Examples are ticks and mites. Individuals of this class have one pair of appendages per segments, heterotrophic, and poisonous.
Individuals are unsegmented coelomates.
Third largest phylum of animals. Example is a nudibranch. Living and ancient representatives called sea lilies. Most intelligent, and largest invertebrates. Examples are Trichinella and Ascaris .