Priapulida is a term used to describe a phylum of marine worms with a unique morphology. These creatures are commonly referred to as penis worms due to their phallic appearance and long, tubular bodies. However, there are several other synonyms that can also be used to describe these peculiar creatures, including marine arrow worms, spiny-headed worms, and echiuran worms. Despite their unusual appearance, priapulids play an important role in marine ecosystems and are often used as indicators of environmental health. With their distinctive features and fascinating biology, priapulids are a fascinating subject for researchers and marine enthusiasts alike.