Palζos:		Lophotrochozoa
METAZOA		Lophotrochozoa

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Lophotrochozoa

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Protostomia |--Ecdysozoa `--Lophotrochozoa |--Bryozoa `--"Procoelomates" |--MOLLUSCA `--+--Annelida `--+--Scalidophora `--BRACHIOPODA

Introduction Phylogeny Links

Introduction

The ancestral Lophotrochozoan?

The Lophotrochozoa are a diverse group that were only recently discovered through molecular phylogeny (if indeed they are not an artifact of the analysis). The name combines the two clades, the Lophorata (which feed via a fringe of hollow tentacles, a lophophore) and the Trochozoa (which have a unique larval stage). Giribet & Ribera use Spiralia and those protostome phyla with spiralian embryo development (Platyhelminthes, Nemertini, Annelida, Sipuncula, Pogonophora [including Vestimentifera], Echiura, Entoprocta, and probably Bryozoa, Rotifera and Acanthocephala).  Aguinaldo et al. (1997) use the term Lophotrochozoa instead of Spiralia to refer to annelids, molluscs, lophophorates and a few other phyla. These Spiralia could perhaps be considered a partial subset of the Lophotrochozoa, although both terms refer to the non-moulting protostome clade.

Phylogeny

The following are cladograms by Peterson & Eernisse (2001), showing the relationships between the Lophotrochozoan groups:

Parsimony analysis of 18s rDNA

Combined parsimony analysis of morphology and 18s rDNA

According to Conway Morris (1993), three of the most important Lophotrochozoan phyla - the molluscs, annelids, and brachiopods (see cladogram above) can be traced back to Cambrian "coat of mail" animals like the Halkeriids; these organisms I have referred to as "Procoelomates".

Note that Conway Morris's findings (palaeontology) are at variance with those of Peterson and Eernisee (molecular biology). According to Conway Morris, annelids and brachiopods are more closely related to each than either is to molluscs (both descending from a common ancestor rather like Halkeria). According to Peterson and Eernisee, molluscs and annelids (Trochozoa - "tro" in the diagram) and are more closely related to each than either is to brachiopods (lophophorates - "lop" in the diagram here)

Tentative Lophotrochozoan phylogeny combining Conway Morris (1993) with Peterson &Eernisse (2001)

<==o LOPHOTROCHOZOA
   `--+--Rhabditophora (Platyhelminthes - flatworms in part)
      `--+-- Entoprocta 
         |-- Bryozoa [Ectoprocta]
         |--+-- †Chancelloriida
         |  `-- †Sachitida
         `--+-- †Siphogonuchitida
            `--+--o "MOLLUSCOMORPHA"
               |  `--+?- †Tullimonsterida
               |     `--+-- Mollusca  (chitons, snails, bivalves, cephalopods, etc.)
               |        `--+-- †Hyolitha
               |           `-- Sipuncula [Sipunculoidea] 
               |--+--o †Halkieriida
               |  `-- †Halkeria evangelista
               |--o "ANNELIDAMORPHA"
               |  |?- †Wiwaxia corrugata
               |  `--+?- †Canadia spinosa
               |     |--+-- †Amiskwiida
               |     |  `-- Nemertea [Nemertinea] 
               |     `--+-- Lobatocerebrida
               |        `--+--+-- †Banffida
               |           |  `-- Echiura [Echiuroidea] 
               |           `-- Annelida [+ Vestimentifera & Pogonophora sensu Rouse, 2001]  
               `--+--o LOPHOPHORATA
                  |  |-- Phoronida 
                  |  `--+-- †Tommotiida
                  |     `-- Brachiopoda 
                  `--+-- †Palaeoscolecida
                     `--+-- Kinorhyncha 
                        `--+-- Loricifera 
                           `-- Priapulida [Priapuloidea]

Links

Links

Introduction to the Lophotrochozoa

Text by M. Alan Kazlev
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