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The Phylogenetic Position of Entoprocta, Ectoprocta, Phoronida, and Brachiopoda1
1 Zoological Museum (University of Copenhagen), Universitetsparken 15, DK-2100-Copenhagen, Denmark
Ectoprocts, phoronids and brachiopods are often dealt with under the heading Tentaculata or Lophophorata, sometimes with entoprocts discussed in the same chapter, for example in Ruppert and Barnes (1994). The Lophophorata is purported to be held together by the presence of a "lophophore," a mesosomal tentacle crown with an upstream-collecting ciliary band. However, the mesosomal tentacle crown of pterobranchs has upstream-collecting ciliary bands with monociliate cells, similar to those of phoronids and brachiopods, although its ontogeny is not well documented. On the contrary, the ectoproct tentacle crown carries a ciliary sieving system with multiciliate cells and the body does not show archimery, neither during ontogeny nor during budding, so the tentacles cannot be characterized as mesosomal. The entoprocts have tentacles without coelomic canals and with a downstream-collecting ciliary system like that of trochophore larvae and adult rotifers and serpulid and sabellid annelids. Planktotrophic phoronid and brachiopod larvae develop tentacles at an early stage, but their ciliary system resembles those of echinoderm and enteropneust larvae. Ectoproct larvae are generally non-feeding, but the planktotrophic cyphonautes larvae of certain gymnolaemates have a ciliary band resembling that of the adult tentacles. The entoprocts have typical trochophore larvae and many feed with downstream-collecting ciliary bands. Phoronids and brachiopods are thus morphologically on the deuterostome line, probably as the sister group of the "Neorenalia" or Deuterostomia sensu stricto. The entoprocts are clearly spiralians, although their more precise position has not been determined. The position of the ectoprocts is uncertain, but nothing in their morphology indicates deuterostome affinities. "Lophophorata" is thus a polyphyletic assemblage and the word should disappear from the zoological vocabulary, just as "Vermes" disappeared many years ago.
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