#priapulida

(Sources - 1, 2, 3, 4)

Priapulida is a phylum of unsegmented marine worms commonly known as “Penis Worms,” due to their general shape and retractable proboscis.

Like kinorhynchs (which seem to be their closest relatives) they live in the mud of shallow waters worldwide. Larger species tend to live in colder seas while smaller species live in warmer waters. They range from 0.2–0.3 cm to 39 cm (15.35 in) long. Their body is divided into a main trunk/abdomen and a swollen proboscis region, called the presoma, ornamented with ridges. The presoma, with the mouth at the tip, can be retracted into the trunk and is used in locomotion as well as in feeding. Members of the family Chaetostephanidae secrete a gelatinous tube, open in both ends, which they live in. Most families are carnivores that feed on slow moving invertebrates such as annelids, but some feed on detritus while others are filter-feeders. They have separate sexes, and usually breed by releasing sperm and eggs into the water, though at least one species is known for internal fertilization.

Priapulid-like fossils are known from the Middle Cambrian, with modern groups appearing in the Carboniferous. They were likely major predators of the Cambrian seas. The mouth of priapulids seems to be an original trait inherited from the last common ancestor of both priapulids and arthropods, though arthropods no longer possess it.

Propaganda under the cut

Kinorhyncha. This phylum is made up of tiny benthic organisms, known as mud dragons

Priapulida. This phylum is made up of unsegmented marine worms known as penis worms.

Priapulida: Penis Worms. So named due to their proboscis, which can be inverted outside of their bodies for feeding. These hardy shallow-burrowing species can be found in intertidal mud flats all over the globe. Its branching "caudal appendage" on its tail end may serve as an anchor, or it may help the worm breathe in low-oxygen waters. While most are detritivores and filter feeders, some have developed adaptations to become predators.

#360 Wynaut

#202 Wobbuffet Wobbuffet: The penis worm. look it up. Actually, don’t. Instead, look up  Priapulida