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

  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},
  volume={9 1},
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.



The demise of a phylum of protists: phylogeny of Myxozoa and other parasitic cnidaria.

Reassessment of myxozoans as metazoans reveals terminal differentiation, typical metazoan cellular junctions, and collagen production, and it is recommended that the group as a whole be removed from all protistan classifications and placed in a more comprehensive cnidarian system.

Are the Platyhelminthes a monophyletic primitive group? An assessment using 18S rDNA sequences.

It is suggested that parasitic platyhelminthes appeared early in the evolution of the group and form a sister group to a still-unresolved clade made by Nemertodermatida, Lecithoepitheliata, Prolecithophora, Proseriata and Rhabdocoela, and that Seriata is paraphyletic.

Sister-group relationship of Gnathostomulida and Rotifera-Acanthocephala

It is proposed that jaw substructure shows a homology, and thus a sister-group relationship, between Gnathostomulida and the clade containing Rotifera plus Acanthocephala and the relationships among the phyla of lower worms are problematic.

A Cladistic Analysis of Pseudocoelomate (Aschelminth) Morphology

It is concluded that there are 2 main lines of pseudocoelomate evolution: a minor clade (Acanthocephala + Rotifera) defined principally by a syncytial epidermis, intracytoplasmic lamina, and sperms with anterior flagella, and a major clade, defined primarily by a cuticle that is molted.

The phylogenetic position of Rhopalura ophiocomae (Orthonectida) based on 18S ribosomal DNA sequence analysis.

Using the models of minimum evolution and parsimony, phylogenetic analyses were undertaken and the results lend support to the following hypotheses about orthonectids: (1) orthonECTids are more closely aligned with triploblastic metazoan taxa than with the protist or diploblasts considered in this analysis.


Testing specific hypotheses of chaetognath affinities to nematodes, mollusks, acanthocephalans, and deuterostomes supported the monophyly of a chaet Cognatha-nematode clade, and an evolutionary scenario for the origin of the Chaetognatha lineage from a vermiform benthic organism was presented.

Annelida and Arthropoda are Not Sister Taxa: A Phylogenetic Analysis of Spiralian Metazoan Morphology

This study presents a new analysis of 141 independently assembled characters, purported to represent the current state of knowledge of metazoan morphology and embryology, and results in robust support of the Eutrochozoa hypothesis.

Evolution of 28S Ribosomal DNA in Chaetognaths: Duplicate Genes and Molecular Phylogeny

In phylogenetic reconstructions, the two classes of 28S rDNA yield trees that root each other; these clearly demonstrate that the Aphragmophora and PhragMophora are natural groups.

Phylogenetic Relationships among Turbellarian Orders Inferred from 18S rDNA Sequences

It is suggested that the Tricladida evolved in the separate lineage from that of a cluster of the Catenulida, Macrostomida, Lecithoepitheliata, Rhabdocoela, Polycladida, Trematoda and Cestoda after the divergence of the Acoela.

Cycliophora is a new phylum with affinities to Entoprocta and Ectoprocta

The structure and function of the cilia suggest a phylogenetic position in Protostomia, while some aspects of inner budding and brooding of larvae are similar to those of Entoprocta and Ectocta.