Scalidophora
Proposed taxonomic clade
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Scalidophora is a group of marine pseudocoelomate ecdysozoans that was proposed on morphological grounds to unite three phyla: the Kinorhyncha, the Priapulida and the Loricifera.[8][9] 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.[10] The introvert and abdomen are separated by a distinct neck region in all groups, but in adult macroscopic priapulids it becomes rudimentary in Priapulus and is completely absent in Halicryptus.[11] However, the monophyly of the Scalidophora was not supported by two molecular studies, where the position of the Loricifera was uncertain[8] or as sister to the Panarthropoda.[9] Both studies supported a reduced Scalidophora comprising the Kinorhyncha and Priapulida as sister phyla. Their closest relatives are the Panarthropoda, Nematoda and Nematomorpha.
| Scalidophora | |||
|---|---|---|---|
| |||
| Ottoia prolifica from the Walcott Quarry of the Burgess Shale (Middle Cambrian) near Field, British Columbia, Canada. | |||
Scientific classification  | |||
| Kingdom: | Animalia | ||
| Subkingdom: | Eumetazoa | ||
| Clade: | ParaHoxozoa | ||
| Clade: | Bilateria | ||
| Clade: | Nephrozoa | ||
| Clade: | Protostomia | ||
| Superphylum: | Ecdysozoa | ||
| Clade: | Scalidophora Lemburg, 1995 | ||
| Phyla | |||
| |||
| Synonyms | |||
|
Cephalorhyncha, Priapozoa | |||
The genus Markuelia, known from fossilized embryos from the middle Cambrian, is thought to be a stem scalidophoran.
The group has also been considered a single group, Cephalorhyncha,[12] with three classes.
The group is named after the spines (scalids) covering the introvert (head that can be retracted into the trunk).[13]
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