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The Platyhelminthes and the Acoela (3871 words) |
 | Their sister-group relationship is strongly supported by similarities in their ciliation (nemertodermatids have their cilia interconnected by ciliary rootlets and have shelfed tips), and similarities in body-wall structure (reduction of extracellular matrix), reproductive organs (lack of sperm ducts and lack of female ducts), and the relation of the statocyst to the nervous tissue. |
| Such a claim is actually not new: Haszprunar (1996) also proposed a basal position for the Acoelomorpha on the basis of the lack of paired cerebral ganglia, lack of an orthogonal nervous system, and lack of ultrafiltration nephridia. |
| Separating the Acoelomorpha from the others as a distinct phylum is a reasonable, if still controversial, move, at least serving to focus attention on the Acoelomorpha which, no matter how it is approached, is a phylogenetically important group. |
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