Gnathostomulida--an enigmatic metazoan phylum from both morphological and molecular perspectives.

@article{Littlewood1998GnathostomulidaanEM,
  title={Gnathostomulida--an enigmatic metazoan phylum from both morphological and molecular perspectives.},
  author={D. Timothy J. Littlewood and Maximilian J. Telford and K. A. Clough and Klaus Rohde},
  journal={Molecular phylogenetics and evolution},
  year={1998},
  volume={9 1},
  pages={
          72-9
        }
}
On the basis of few and contentious morphological characters Gnathostomulids have been thought to be the sister-group of either the Platyhelminthes or the Syndermata (Rotifera + Acanthocephala). We provide a full 18S rDNA sequence for a species of Gnathostomula and attempt to resolve its position among the Metazoa, on the basis of molecular evidence. Sixty sequences, representing 30 nominal phyla and including new entoproct and gastrotrich sequences, were used to reconstruct phylogenies using… 

Identification of chaetognaths as protostomes is supported by the analysis of their mitochondrial genome.

The complete mitochondrial DNA genome of Spadella cephaloptera is determined, it is the smallest metazoan mitochondrial genome known and lacks both atp8 and atp6 and all tRNA genes, and phylogenetic reconstructions show that Chaetognatha belongs to protostomes.

The position of the Arthropoda in the phylogenetic system

There are morphological characters that support Articulata, but molecular as well as morphological data advocate Ecdysozoa, and comparative morphology suggests Gastrotricha as the sister group of Ecdy sozoa with the synapomorphies.

Myzostomida Are Not Annelids: Molecular and Morphological Support for a Clade of Animals with Anterior Sperm Flagella

A phylogenetic analysis of 18S and 28S ribosomal DNA sequence data of Myzostoma glabrum is presented to show that myzostomes are a sister group of the Cycliophora, closely related to the rotifer‐acanthocephalan clade (=Syndermata).

Triploblastic Relationships with Emphasis on the Acoelomates and the Position of Gnathostomulida, Cycliophora, Plathelminthes, and Chaetognatha: A Combined Approach of 18S rDNA Sequences and Morphology

The 18S ribosomal sequence data for 145 terminal taxa and 276 morphological characters coded for 36 supraspeci(cid:142)c taxa were combined in a total evidence regime to determine the most consistent picture of triploblastic relationships for these data.

Triploblastic relationships with emphasis on the acoelomates and the position of Gnathostomulida, Cycliophora, Plathelminthes, and Chaetognatha: a combined approach of 18S rDNA sequences and morphology.

For the first time, a data analysis recognizes a clade of acoelomates, the Platyzoa, which is expanded to include the enigmatic phylum Cycliophora, as sister group to Syndermata.

Gnathostomulid phylogeny inferred from a combined approach of four molecular loci and morphology

DNA sequence data from four molecular loci, including 18S rRNA, 28S r RNA, histone H3 and cytochrome c oxidase subunit I, are added to a revised morphological data matrix and clearly support gnathostomulid monophyly, as well as the basal division of Gnathstomulida into Filospermoidea and Bursovaginoidea.

Phylogenetic Relationships of Acanthocephala Based on Analysis of 18S Ribosomal RNA Gene Sequences

Analysis of the nearly complete 18S rRNA genes of nine species from the three classes of Acanthocephala and four species ofRotifera found statistically significant support for the monophyly of Rotifera, represented in the analysis byspecies from the clade Eurotatoria, which includes the classes Bdelloidea and Monogononta.

On the Phylogenetic Position of Rotifera – Have We Come Any Further?

The phylogenetic position of rotifers with regard to the gnathifera is discussed, and cladistic studies using molecular data, morphological characters or total evidence suggest a sister group relationship between Cycliophora and Entoprocta.

Phylogenomic analyses of lophophorates (brachiopods, phoronids and bryozoans) confirm the Lophotrochozoa concept

These analyses show that the three lophophorate lineages are affiliated with trochozoan rather than deuterostome phyla, and all hypotheses claiming that they are more closely related to Deuterstomia than to Protostomia can be rejected by topology testing.

On the phylogenetic position of Rotifera — have we come any further?

The phylogenetic position of rotifers with regard to the gnathifera is discussed, and cladistic studies using molecular data, morphological characters or total evidence suggest a sister group relationship between Cycliophora and Entoprocta.
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