Scalidophora
The group is named after the spines, scalids, covering the introvert, the head that can be retracted into the trunk.
Zoology
Scalidophora are marine pseudocoelomate protostomes. They have chitinous cuticle that is moulted, rings of scalids on the introvert, flosculi, and two rings of introvert retracts.
Taxonomy
The monophyly of the Scalidophora is not supported by molecular studies. The position of the Loricifera was uncertain, or as sister to the Panarthropoda. 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. The group has also been considered a single group, Cephalorhyncha, with three classes.
Subclasses
Kinorhyncha
Priapulida
Loricifera