Tunicates and not cephalochordates are the closest living relatives of vertebrates

  title={Tunicates and not cephalochordates are the closest living relatives of vertebrates},
  author={Fr{\'e}d{\'e}ric Delsuc and Henner Brinkmann and Daniel Chourrout and Herv{\'e} Philippe},
Tunicates or urochordates (appendicularians, salps and sea squirts), cephalochordates (lancelets) and vertebrates (including lamprey and hagfish) constitute the three extant groups of chordate animals. Traditionally, cephalochordates are considered as the closest living relatives of vertebrates, with tunicates representing the earliest chordate lineage. This view is mainly justified by overall morphological similarities and an apparently increased complexity in cephalochordates and vertebrates… 

Deuterostome phylogeny reveals monophyletic chordates and the new phylum Xenoturbellida

To study the relationships among all deuterostome groups, an alignment of more than 35,000 homologous amino acids is assembled, including new data from a hemichordate, starfish and Xenoturbella and it is concluded that chordates are monophyletic.

Deciphering deuterostome phylogeny: molecular, morphological and palaeontological perspectives

  • B. SwallaA. Smith
  • Biology
    Philosophical Transactions of the Royal Society B: Biological Sciences
  • 2008
Molecular phylogenies, larval morphology and the adult heart/kidney complex all support echinoderms and hemichordates as a sister grouping (Ambulacraria), andGene network data suggest that the ancestral deuterostome ancestor had an anterior–posterior body axis specified by Hox and Wnt genes, and was bilaterally symmetrical with left–right asymmetry determined by expression of nodal.

Characterization of microRNAs in cephalochordates reveals a correlation between microRNA repertoire homology and morphological similarity in chordate evolution

The miRNA contents demonstrated a clear correlation between the extent of miRNA overlapping and morphological similarity among the three chordate groups, providing a strong evidence of miRNAs being the major genetic factors driving morphological complexity in early chordate evolution.

The phylum Vertebrata: a case for zoological recognition

It is suggested that it is more appropriate to recognize vertebrates as an independent phylum, not as a subphylum of the phylum Chordata.

Analysis of the Amphioxus Genome

Seventeen ancestral chordate linkage groups that are conserved in the modern amphioxus and vertebrate genomes are revealed by highly conserved synteny between the two genomes.

An Advanced Filter-Feeder Hypothesis for Urochordate Evolution

An advanced filter-feeder hypothesis is presented, in which, although the taxonomic position of larvaceans is enigmatic, it is argued that among urochordates, free-living larvACEans are basal, while sessile ascidians are derived.

Chordate evolution and the three-phylum system

It is proposed that an evolutionary occurrence of tadpole-type larvae is fundamental to understanding mechanisms of chordate origin and should be classified at the superphylum level, with the Chordata further subdivided into three phyla, on the basis of their distinctive characteristics.

Metaphylogeny of 82 gene families sheds a new light on chordate evolution

It is shown that the urochordate phyla is the vertebrate sister group and that gene loss played a major role in structuring the uoChordate genome.


The view of the chordate ancestor has changed during the past 10 years and is shown to be a benthic worm with a mouth and pharyngeal gill slits supported by cartilaginous gill bars.

microRNAs reveal the interrelationships of hagfish, lampreys, and gnathostomes and the nature of the ancestral vertebrate

Fundamental conservation of microRNA expression patterns among lamprey, hagfish, and gnathostome organs, implying that the role of microRNAs within specific organs is coincident with their appearance within the genome and is conserved through time, support the monophyletic of cyclostomes and suggest that the last common ancestor of all living vertebrates was a more complex organism than conventionally accepted.



Multigene analyses of bilaterian animals corroborate the monophyly of Ecdysozoa, Lophotrochozoa, and Protostomia.

This study demonstrates that the incongruences observed between rRNA and multigene analyses were indeed due to long-branch attraction artifacts, illustrating the enormous impact of systematic biases on phylogenomic studies and suggests that urochordates are more closely related to vertebrates than are cephalochordates.

Xenoturbella is a deuterostome that eats molluscs

It is shown that the samples in these studies were contaminated by bivalve embryos eaten by Xenoturbella and that XenOTurbella is in fact a deuterostome related to hemichordates and echinoderms.

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Molecular phylogeny and divergence times of deuterostome animals.

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Key characters uniting hemichordates and chordates: homologies or homoplasies?

A cladistic analysis of Deuterostomia, based partly on homologs discussed in this paper, indicates a sister-taxon relationship between Urochordata and Vertebrata, with Cephalochordata as the plesiomorphic clade.

Hox cluster disintegration with persistent anteroposterior order of expression in Oikopleura dioica

It is shown that the tunicate Oikopleura dioica has a complement of nine Hox genes in which all central genes are lacking but a full vertebrate-like set of posterior genes is present.

The chordate amphioxus: an emerging model organism for developmental biology

The cephalochordate amphioxus is the closest living invertebrate relative of the vertebrates and ideal as a model organism for understanding mechanisms of vertebrate development.

Phylogenomics of eukaryotes: impact of missing data on large alignments.

This large data set provides a reliable phylogenetic framework for studying eukaryotic and animal evolution and will be easily extendable when large amounts of sequence information become available from a broader taxonomic range.