Bryozoa ("Moss animals") are tiny creatures with a ring of tentacles surrounding the mouth. The phylum Bryozoa has been divided into several phyla that are quite likely unrelated: the
Ectoprocta, the
Entoprocta, and the
Cycliophora. Almost always the first of the three is meant.
Bryozoa is one of the few classical phyla from which no members have been found in the Cambrian. They seem to have evolved in the Ordovician.