Temporal range: Early Cambrian - Recent
|Caribbean Reef Squid or Sepioteuthis sepioidea is a complex lophotrochozoan.|
Halanych et al., 1995
The Lophotrochozoa (//, "crest/wheel animals") are a major grouping of protostome animals. The taxon was discovered based on molecular data. Molecular evidence such as a result of studies of the evolution of small-subunit ribosomal RNA (rRNA) supports the monophyly of the phyla listed in the infobox shown at right.
The word "lophotrochozoan" is sometimes equated with spiralian. When used in a broader sense (sensu lato), it can include rotifers and platyhelminthes. When used sensu stricto, it refers to a subgroup of Spiralia.
The Lophotrochozoa comprise two groups, the trochozoans and the lophophorata. The exact relationships between the different phyla are not entirely certain.
- Trochozoans produce trochophore larvae, which have two bands of cilia around their middle. Previously these were treated together as the Trochozoa, together with the arthropods, which do not produce trochophore larvae but were considered close relatives of the annelids because they are both segmented. However, they show a number of important differences, and the arthropods are now placed separately among the Ecdysozoa. The Trochozoa include the Nemertea, Mollusca, Sipuncula, and Annelida.
- The Lophophorata are united by the presence of a lophophore, a fan of ciliated tentacles surrounding the mouth, and so were treated together as the lophophorates. They are unusual in showing radial cleavage, and some authors considered them deuterostomes. The ‘clade’ Lophotrochozoa was founded on evidence from 18S ribosomal RNA (1), but a later study on LSU and SSU ribosomal genes showed that the Lophophorata is polyphyletic (9). The Lophophorata include the Bryozoa, Entoprocta, Phoronida, and Brachiopoda.
Other phyla are included on the basis of molecular data.
|A phylogenetic tree of the Lophotrochozoa|
- Debate about Cambrian Lophotrochozoans
Additional reference: 9. Passamaneck Y & Halanych KM. 2006. Lophotrochozoan phylogeny assessed with LSU and SSU data: evidence of lophophorate polyphyly. Mol Phylogenet Evol 40:20–28.
- Podsiadlowski R. 2009. Phylogeny and mitochondrial gene order variation in Lophotrochozoa in the light of new mitogenomic data from 10.1186/1471-2164-10-364