A phylum, first described in 1983 by R. M. Kristensen (1948– ), of animals only 0.25 mm long that live in marine gravel. The body bears a cuticle of four plates (one dorsal, one ventral, two lateral) and has recurved spines on the anterior end. The anus is terminal. Sexes are separate; larvae resemble small adults. The phylum appears to be related to the Priapulida (priapus worms) and Kinorhyncha.
Subjects: Ecology and Conservation — Zoology and Animal Sciences.