Deuterostome phylogeny - a molecular perspective

Molecular data improved our knowledge on deuterostome phylogeny and challenged traditional hypotheses. Basically, deuterostomes split in monophyletic Ambulacaria, Xenacoelomorpha, and Chordata. Within Ambulacraria, the sister-taxa Echinodermata and Hemichordata are supported in numerous studies. Mitogenomic analyses support the echinoderm monophyly as well as the monophyly of the five major clades Asteroidea, Crinoidea, Echinoidea, Holothuridea, and Ophiuroidea.However, their mutual relationships remain ambiguous. Likewise, the placementof hemichordate subtaxa is still fluent, most analyses showing Pterobranchia to be nested in paraphyletic enteropneusts. Chordata are subdivided in Cephalochordata and Olfactores, in which the latter includes the two sister-taxa Tunicata and Vertebrata.Inside Tunicata three clades are distinguishable: (Phlebobranchia + Thaliacea + Aplousobranchia), Appendicularia, and Stolidobranchia. Finally, Vertebrata comprise the sister-taxa Gnathost omata and Cyclostomata, the latter containing Hyperoartia and Hyperotreti. Within Gnathostomata sequencing of the coelacanth genome and lungfish transcriptome has resolved a long standing issue by supporting the lungfish-tetrapod dichotomy.