Lophotrochozoa

Lophotrochozoa (, "crest/wheel animals") is a clade of protostome animals within the Spiralia. The taxon was established as a monophyletic group based on molecular evidence. The clade includes animals like annelids, molluscs, bryozoans, and brachiopods.

The Mesozoa are minuscule, worm-like parasites of marine invertebrates. Generally, these tiny, elusive creatures consist of a somatoderm (outer layer) of ciliated cells surrounding one or more reproductive cells.

right|thumb|The anatomy of a trochophore A - episphere B - hyposphere 1 - ganglion|ganglia 2 - apical tuft 3 - prototroch 4 - metatroch 5 - nephridium 6 - anus 7 - protonephridia 8 - gastrointestinal tract 9 - buccal opening 10 - [[blastocoele]]

The Trochozoa are a proposed Lophotrochozoa clade that is a sister clade of Bryozoa and Platyzoa. The clade would include animals in five phyla: the Nemertea, the Annelida, the Mollusca, and the two Brachiozoan phyla, Brachiopoda and Phoronida. Both annelids and molluscs have been suggested as the sister group of Brachiozoa. It has also been proposed that nemerteans are actually a clade of annelids.

Namacalathus is a problematic metazoan fossil occurring in the latest Ediacaran. The first, and only described species, N. hermanastes, was first described in 2000 from the Nama Group of central and southern Namibia.

Odontogriphus (from , 'tooth' and , 'riddle') is a genus of soft-bodied animals known from middle Cambrian Lagerstätte. Reaching as much as in length, Odontogriphus is a flat, oval bilaterian which apparently had a single muscular foot and a "shell" on its back that was moderately rigid but of a material unsuited to fossilization.

Parenchymia is a proposed clade encompassing Nemertea and Platyhelminthes. The clade was suggested in a 2019 study showing the clade as a sister to Annelida, with both groups together being sister to Lophophorata. The synapomorphies include similar organization of ciliary bands in the larva of both groups, as well as a lack of chitin, and is named for the abundant parenchyma found between the body wall and internal organs of both. A similar taxon, with Mollusca being likewise linked together with Symbion and Entoprocta, has been proposed in a clade called Tetraneuralia.

Tetraneuralia is a proposed clade of spiralian bilaterians uniting the phyla Mollusca and Entoprocta. belonging to Lophotrochozoa that groups mollusks, entoprocts and the extinct family Cupithecidae. The clade is supported by several morphological similarities between the two and has turned out to be important for evolution of mollusks.