Lophotrochozoa was defined in 1995 as the "last common ancestor of the three traditionallophophorate taxa (brachiopods,bryozoans, andphoronid worms), themollusks and theannelids, and all of the descendants of that common ancestor".[5] It is acladistic definition (a node-based name), so the affiliation to Lophotrochozoa of spiralian groups not mentioned directly in the definition depends on the topology of thespiralian tree of life, and in some phylogenetic hypotheses, Lophotrochozoa may even be synonymous to Spiralia.Nemertea andOrthonectida (if not directly considered as part ofAnnelida) are probably lophotrochozoan phyla;Dicyemida,Gastrotricha, andPlatyhelminthes may be lophotrochozoans or placed in theRouphozoa clade outside Lophotrochozoa;Chaetognatha,Gnathostomulida,Micrognathozoa, andSyndermata are probablygnathiferans and so placed as a basal spiralian clade outside Lophotrochozoa;Cycliophora could be a gnathiferan or a lophotrochozoan phylum. One of the candidate hypotheses is presented below.
In the most recent research, the three phyla Cycliophora, Entoprocta and Bryozoa makes up a single clade and are the first to branch off from the other lophotrochozoans. The second split is the molluscs, and the third consists of two sister phyla, annelids and nemerteans. Lastly remains the clade that consist of the phoronids and the brachiopods.[16][17]
A number of fossil taxa can be identified as early Lophotrochozoans, even if their precise affinity remains contested. However, relevant Cambrian fossils are debated.
The clade Lophotrochozoa is named after the two distinct characteristics of its members; thelophophore, a feeding structure consisting of a ciliated crown of tentacles surrounding a mouth, and the developmental stage of thetrochophore larva.Lophophorata such asBrachiozoa andBryozoa have lophophores, while members ofTrochozoa such asmolluscs andannelids have trochophore larvae, although some may have none.[19][20]
^Halanych, K. M.; Bacheller, J.; Liva, S.; Aguinaldo, A. A.; Hillis, D. M.; Lake, J. A. (17 March 1995). "18S rDNA evidence that the Lophophorates are Protostome Animals".Science.267 (5204):1641–1643.doi:10.1126/science.7886451.PMID7886451.S2CID12196991.
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Data related toLophotrochozoa at Wikispecies
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