Change search
ReferencesLink to record
Permanent link

Direct link
Xenacoelomorpha is the sister group to Nephrozoa
Swedish Museum of Natural History, Department of Zoology. Auburn University.ORCID iD: 0000-0002-3920-7741
Sars International Centre for Marine Molecular Biology.
Winthrop University.
Swedish Museum of Natural History, Department of Bioinformatics and Genetics.
Show others and affiliations
2016 (English)In: Nature, ISSN ISSN: 0028-0836, Vol. 530, 89-93 p.Article in journal (Refereed) Published
Abstract [en]

The position of Xenacoelomorpha in the tree of life remains a major unresolved question in the study of deep animal relationships1. Xenacoelomorpha, comprising Acoela, Nemertodermatida, and Xenoturbella, are bilaterally symmetrical marine worms that lack several features common to most other bilaterians, for example an anus, nephridia, and a circulatory system. Two conflicting hypotheses are under debate: Xenacoelomorpha is the sister group to all remaining Bilateria (= Nephrozoa, namely protostomes and deuterostomes)2,3 or is a clade inside Deuterostomia4. Thus, determining the phylogenetic position of this clade is pivotal for understanding the early evolution of bilaterian features, or as a case of drastic secondary loss of complexity. Here we show robust phylogenomic support for Xenacoelomorpha as the sister taxon of Nephrozoa. Our phylogenetic analyses, based on 11 novel xenacoelomorph transcriptomes and using different models of evolution under maximum likelihood and Bayesian inference analyses, strongly corroborate this result. Rigorous testing of 25 experimental data sets designed to exclude data partitions and taxa potentially prone to reconstruction biases indicates that long- branch attraction, saturation, and missing data do not influence these results. The sister group relationship between Nephrozoa and Xenacoelomorpha supported by our phylogenomic analyses implies that the last common ancestor of bilaterians was probably a benthic, ciliated acoelomate worm with a single opening into an epithelial gut, and that excretory organs, coelomic cavities, and nerve cords evolved after xenacoelomorphs separated from the stem lineage of Nephrozoa. 

Place, publisher, year, edition, pages
2016. Vol. 530, 89-93 p.
National Category
Natural Sciences
Research subject
Diversity of life
URN: urn:nbn:se:nrm:diva-1844DOI: 10.1038/nature16520OAI: diva2:1037430
Swedish Research Council, 2012-3913Swedish Research Council, 2014-5901
Available from: 2016-10-14 Created: 2016-10-05 Last updated: 2016-10-17Bibliographically approved

Open Access in DiVA

fulltext(21897 kB)4 downloads
File information
File name FULLTEXT01.pdfFile size 21897 kBChecksum SHA-512
Type fulltextMimetype application/pdf

Other links

Publisher's full text

Search in DiVA

By author/editor
Cannon, JohannaRonquist, FredrikJondelius, Ulf
By organisation
Department of ZoologyDepartment of Bioinformatics and Genetics
Natural Sciences

Search outside of DiVA

GoogleGoogle Scholar
Total: 4 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 6 hits
ReferencesLink to record
Permanent link

Direct link