Tunicates and not cephalochordates are the closest living relatives of vertebrates

@article{Delsuc2006TunicatesAN,
  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},
  journal={Nature},
  year={2006},
  volume={439},
  pages={965-968}
}
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… 

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