them difficult to classify. [5] Creditpointe Dr. - 9:45am - Protostomia - 590mya   Worms, insects (arthropods), crustaceans, barnacles & octopus (molluscs)   Protostomia  (from  Greek  meaning "mouth first") are a  clade  of  animals . Together with the  deuterostomes  and a few smaller  phyla , they make up the  Bilateria ,