| Priapulidae Temporal range: | |
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| Priapulus caudatus | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Priapulida |
| Class: | Priapulimorpha |
| Order: | Priapulimorphida |
| Family: | Priapulidae Gosse, 1855 |
| Genera | |
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Priapulidae is the canonical family of priapulid worms, comprising Priapulus and Priapulosis as well as the Carboniferous genus Priapulites. [1]
Classification and maximum trunk length: [2] [3] [4]
Priapulida, sometimes referred to as penis worms, is a phylum of unsegmented marine worms. The name of the phylum relates to the Greek god of fertility, because their general shape and their extensible spiny introvert (eversible) proboscis may resemble the shape of a human penis. They live in the mud and in comparatively shallow waters up to 90 metres (300 ft) deep. Some species show a remarkable tolerance for hydrogen sulfide, anoxia and low salinity. Halicryptus spinulosus appears to prefer brackish shallow waters. They can be quite abundant in some areas. In an Alaskan bay as many as 85 adult individuals of Priapulus caudatus per square meter has been recorded, while the density of its larvae can be as high as 58,000 per square meter.
Ottoia is a stem-group archaeopriapulid worm known from Cambrian fossils. Although priapulid-like worms from various Cambrian deposits are often referred to Ottoia on spurious grounds, the only clear Ottoia macrofossils come from the Burgess Shale of British Columbia, which was deposited 508 million years ago. Microfossils extend the record of Ottoia throughout the Western Canada Sedimentary Basin, from the mid- to late- Cambrian. A few fossil finds are also known from China.
Scalidophora is a group of marine pseudocoelomate protostomes that was proposed on morphological grounds to unite three phyla: the Kinorhyncha, the Priapulida and the Loricifera. The three phyla have four characters in common — chitinous cuticle that is moulted, rings of scalids on the introvert, flosculi, and two rings of introvert retracts. However, the monophyly of the Scalidophora was not supported by two molecular studies, where the position of the Loricifera was uncertain or as sister to the Panarthropoda. Both studies supported a reduced Scalidophora comprising the Kinorhyncha and Priapulida as sister phyla. Their closest relatives are the Panarthropoda, Nematoda and Nematomorpha; thus, they are placed in the group Ecdysozoa.
Corophium is a genus of the amphipod family Corophiidae. Formerly a much larger genus, many species have been transferred to segregate genera such as Monocorophium and Crassicorophium.
Fieldia is a genus of worms known from the Cambrian Burgess Shale, and assigned to the priapulids. It was originally interpreted as an arthropod; its trunk bears a dense covering of spines, and its proboscis is small. It fed on sea-floor mud, evidenced by the frequent presence of sediments preserved in its gut.
Ancalagon minor is an extinct priapulid worm known from the Cambrian Burgess Shale.
Archaeopriapulida is a group of priapulid worms known from Cambrian lagerstätte. The group is closely related to, and very similar to, the modern Priapulids. It is unclear whether it is mono- or polyphyletic. Despite a remarkable morphological similarity to their modern cousins, they fall outside of the priapulid crown group, which is not unambiguously represented in the fossil record until the Carboniferous. In addition to well-preserved body fossils, remains of several archaeopriapulid taxa are known to have been preserved primarily as organic microfossils, such as isolated scalids and pharyngeal teeth. They are probably closely related or paraphyletic to the palaeoscolecids; the relationship between these basal worms is somewhat unresolved.
The palaeoscolecids are a group of extinct ecdysozoan worms resembling armoured priapulids. They are known from the Lower Cambrian to the late Silurian; they are mainly found as disarticulated sclerites, but are also preserved in many of the Cambrian lagerstätten. They take their name from the typifying genus Palaeoscolex. Other genera include Cricocosmia from the Lower Cambrian Chengjiang biota. Their taxonomic affinities within Ecdysozoa have been the subject of debate.
Maccabeus is the sole genus of seticoronarian priapulid worms. It dwells inside an agglutinated tube.
Louisella is a genus of worm known from the Middle Cambrian Burgess Shale. It was originally described by Charles Walcott in 1911 as a holothurian echinoderm, and represents a senior synonym of Miskoia, which was originally described as an annelid. 48 specimens of Louisella are known from the Greater Phyllopod bed, where they comprise < 0.1% of the community. It has been stated to have palaeoscolecid-like sclerites, though this is not in fact the case.
The fossil taxon Priapulites is the earliest-known crown-group priapulid, and is closely related to the Priapulidae.
Halicryptus is the sole genus of its class of priapulid worms, and grows to great size. It has an important effect on the structure of soft-sediment communities.
Tubiluchidae is one of the two families of priapulimorphidan priapulid worms.
Alveocystis is a genus in the phylum Apicomplexa. Species in this genus infect worms of the family Priapuloidea and molluscs. This genus has been poorly studied and little is known about it.
The polythyridium is a component of the gut that surrounds the entrance of the intestine in priapulids of genus Tubiluchus. It comprises tuberculate and hairy plates associated with a strong muscle. These plates may help to keep unwanted particles out of the gut.
Archotuba is a genus of elongated conical tubes that were seemingly deposited by colonial organisms. Known from the Chengjiang, its biological affinity is uncertain; it somewhat resembles the tubes of the 'priapulid' Selkirkia, but a cnidarian affinity is also possible. In the absence of soft parts, there really isn't enough data to confirm a biological affiliation.
Baetis bicaudatus is a species of small minnow mayfly in the family Baetidae. It is found in southwestern, northern Canada, the western United States, and Alaska.
Priapulus caudatus known as the cactus worm, is a marine invertebrate belonging to the phylum Priapulida. It is a cylindrical, unsegmented worm which burrows in soft sediment on the seabed. It has a circumpolar distribution.
Acanthopriapulus is a genus of priapulids belonging to the family Priapulidae.
Priapulus is a genus of worms belonging to the family Priapulidae.
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