The phylogenetic position of the comb jellies (Ctenophora) and the importance of taxonomic sampling

  title={The phylogenetic position of the comb jellies (Ctenophora) and the importance of taxonomic sampling},
  author={Andreas Wallberg and Mikael Thollesson and James S Farris and Ulf Jondelius},
The transition to a vermiform body shape is one of the most important events in animal evolution, having led to the impressive radiation of Bilateria. However, the sister group of Bilateria has remained obscure. Cladistic analyses of morphology indicate that Ctenophora is the sister group of Bilateria. Previous analyses of SSU rRNA sequences have yielded conflicting results; in many studies Ctenophora forms the sister group of Cnidaria + Bilateria, but in others the ctenophores group with… 

The Genome of the Ctenophore Mnemiopsis leidyi and Its Implications for Cell Type Evolution

The genome of the ctenophore the warty comb jelly or sea walnut, Mnemiopsis leidyi, is sequenced and it is concluded that c tenophores alone, not sponges or the clade consisting of both ctenphores and cnidarians, are the most basal extant animals.

Phylogenetic-signal dissection of nuclear housekeeping genes supports the paraphyly of sponges and the monophyly of Eumetazoa.

The relationships at the base of the metazoan tree have been difficult to robustly resolve, and there are several different hypotheses regarding the interrelationships among sponges, cnidarians,

Dismissal of Acoelomorpha: Acoela and Nemertodermatida are separate early bilaterian clades

We used new 18S and 28S rRNA sequences analysed with parsimony, maximum likelihood and Bayesian methods of phylogenetic reconstruction to show that Nemertodermatida, generally classified as the

A late-surviving stem-ctenophore from the Late Devonian of Miguasha (Canada)

The phylogenetic analyses suggest that the new taxon Daihuoides jakobvintheri gen. et sp.

The early history of the metazoa—a paleontologist’s viewpoint

  • A. Zhuravlev
  • Geography, Environmental Science
    Biology Bulletin Reviews
  • 2015
In the aggregate, modern data from molecular biology, palaeontology, and comparative embryology/morphology, having been revitalized by the introduction of new microscopy techniques, imply that the hypothesized planktotrophic gastrae-like common ancestor is the least likely of the diverse suggestions on the origins of the Metazoa.

Vetigastropod phylogeny and a new concept of Seguenzioidea: independent evolution of copulatory organs in the deep‐sea habitats

Bayesian and maximum‐likelihood phylogenies of Vetigastropoda were reconstructed by separate and combined analyses of one mitochondrial, one nuclear and two nuclear gene sequences, with an emphasis on dense taxonomic sampling.

Placozoans are eumetazoans related to Cnidaria

It is necessary to reconsider the homology of eumetazoan traits not only between ctenophores and bilaterians, but also between cnidarians and bizards, as well as between placozoans and poriferans.

Support for a clade of Placozoa and Cnidaria in genes with minimal compositional bias

This work examines the influence of adding new genomes from placozoans to a large dataset designed to study the deepest splits in the animal phylogeny, and demonstrates that a majority of genes show evidence of compositional heterogeneity, and that support for the Cnidaria + Bilateria clade can be assigned to this source of systematic error.

Poriferan paraphyly and its implications for Precambrian palaeobiology

It is demonstrated, in accordance with previous molecular studies, that sponges are paraphyletic, and that calcisponge are more closely related to eumetazoans than they are to demosponges.



The Nemertodermatida are basal bilaterians and not members of the Platyhelminthes

The results imply that the last common ancestor of bilaterian metazoans was a small, benthic, direct developer without segments, coelomic cavities, nephrida or a true brain.

The position of arthropods in the animal kingdom: Ecdysozoa, islands, trees, and the "Parsimony ratchet".

The goal of this paper was to investigate the position of the Arthropoda within the protostome animals and determine arthropod sister-group relationships, and the phylogenetic conclusions were summarized as monophyletic.

A molecular phylogenetic framework for the phylum Ctenophora using 18S rRNA genes.

The first molecular phylogenetic analysis of the phylum Ctenophora, by use of 18S ribosomal RNA sequences from most of the major taxa, suggests that the ctenophores form a distinct monophyletic group that is most closely related to the cnidarians.

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.

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.

Phylogeny of Medusozoa and the evolution of cnidarian life cycles

To investigate the evolution of cnidarian life cycles, data from the small subunit of the ribosome are used and indicate that Cnidaria is monophyletic and composed of Anthozoa and Medusozoa.

Conflicting phylogenetic signals at the base of the metazoan tree

It is demonstrated that variable rates of evolution among lineages, sensitivity of the analyses to taxon selection, and conflicts in the phylogenetic signal contained in different amino acid sequences obscure the phylogenetically associations among the early branching Metazoa.

Animal phylogeny and the ancestry of bilaterians: inferences from morphology and 18S rDNA gene sequences

Because chaetognaths and lophophorates, taxa traditionally allied with deuterostomes, occupy basal positions within their respective protostomian clades, deuterstomy most likely represents a suite of characters plesiomorphic for bilaterians.

Sponge paraphyly and the origin of Metazoa

The polymerase chain reaction is used to amplify almost the entire nucleic acid sequence of the 18S rDNA from several hexactinellid, demosponge and calcareous sponge species to suggest that sponges are paraphyletic, the Calcarea being more related to monophyletic Eumetazoa than to the siliceous spongees.

Early evolution of the Metazoa and phylogenetic status of diploblasts as inferred from amino acid sequence of elongation factor-1 alpha.

Almost the entire nucleic acid sequence of elongation factor-1 alpha from a sponge, two cnidarians, a ctenophora, and a turbellarian is sequenced and the phylogenetic status of the diploblasts is investigated, which supported the monophyly of the Metazoa.