Trochozoa

The Trochozoa are a collection of several phyla of animals, including most notably the mollusks and annelids, as well as the smaller phyla Nemertea and Sipuncula. They are united by the common presence of trochophore larvae, which have two bands of cilia around the middle.

Originally, the arthropods were also considered to belong here as close relatives of the annelids, though no trochophores occur within the group. More recently this has been called into question, and RNA studies remove them to the Ecdysozoa, though they confirm the unity of the remaining Trochozoa. The lophophorates are often considered close relatives of the Trochozoa, and possibly the rotifers and their allies as well.