Practice question

Priapulida constitute small marine unsegmented ecdysozoan phylum of benthic carnivorous worms characterized by stout cylindrical body with retractable anterior introvert covered with scalid spines and eversible pharynx with teeth, plus posterior trunk annulated. Historically termed penis worms because trunk plus introvert resembles mammalian penis in shape, ranging 3-15 cm though microscopic larvae exist. Cuticle chitinous moulted as ecdysozoans. Scavengers and predators in cold waters, burrow in mud, belonging to Scalidophora alongside Kinorhyncha and Loricifera, retaining some deuterostome-like embryonic traits despite molting growth pattern typical of ecdysozoans and cephalic proboscis.