Xenambulacraria

Xenambulacraria Temporal range: Cambrian–Present PreꞒ Ꞓ O S D C P T J K Pg N
Xenoturbellida ( Xenoturbella japonica ) Acoelomorpha ( Waminoa sp.) Echinodermata ( Thromidia catalai ) Hemichordata ( Balanoglossus sp.)
Examples of all four branches of Xenambulacraria
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Subkingdom:	Eumetazoa
Clade:	ParaHoxozoa
Clade:	Bilateria
Clade:	Xenambulacraria Bourlat et al, 2006 [1]
Clades
Xenacoelomorpha Xenoturbellida Acoelomorpha Ambulacraria Echinodermata Hemichordata

Xenambulacraria is a proposed clade of animals with bilateral symmetry as an embryo, consisting of the Xenacoelomorpha (i.e., Xenoturbella and acoelomorphs) and the Ambulacraria (i.e., echinoderms and hemichordates). ^[1]

If confirmed, the clade would either be the sister group to the chordates (if deuterostomes are monophyletic) or the sister group to all the other bilaterians, grouped together in Centroneuralia (with deuterostomes being paraphyletic). ^{[1] [2] [3] [4]}

Although the validity of the clade relies mostly on phylogenomics, molecular genetics studies have proposed pigment cell clusters expressing polyketide synthase (PKS) and sulfotransferase as a synapomorphy of Xenambulacraria. ^[5]

Phylogeny

Xenambulacraria has usually been recovered as a clade inside of either of two distinct phylogenies.

Basal Xenambulacraria

The following phylogeny assumes a paraphyletic Deuterostomia, with Xenambulacraria at the base of Bilateria. ^[4]

Bilateria	Xenambulacraria Xenacoelomorpha Xenoturbellida Acoelomorpha Ambulacraria Echinodermata Hemichordata Centroneuralia Chordata Protostomia Ecdysozoa Spiralia † Kimberella

Xenambulacraria inside Deuterostomia

The following phylogeny assumes a monophyletic Deuterostomia, with Xenambulacraria nested inside of it.

Bilateria	Deuterostomia Xenambulacraria Xenacoelomorpha Xenoturbellida Acoelomorpha Ambulacraria Echinodermata Hemichordata Chordata Protostomia Ecdysozoa Spiralia † Kimberella

Gallery

• Diversity of Xenambulacrarians
• 
  Various Acoelomorpha (nemertodermatids).
• 
  Various Hemichordata (enteropneusts).
• 
  Various Echinodermata from all extant classes.

References

1. Bourlat, Sarah J.; Juliusdottir, Thorhildur; Lowe, Christopher J.; Freeman, Robert; Aronowicz, Jochanan; Kirschner, Mark; Lander, Eric S.; Thorndyke, Michael; Nakano, Hiroaki; Kohn, Andrea B.; Heyland, Andreas; Moroz, Leonid L.; Copley, Richard R.; Telford, Maximilian J. (2006). "Deuterostome phylogeny reveals monophyletic chordates and the new phylum Xenoturbellida". Nature. 444 (7115): 85–88. Bibcode:2006Natur.444...85B. doi:10.1038/nature05241. ISSN   0028-0836. PMID   17051155. S2CID   4366885.
2. Philippe, Hervé; Poustka, Albert J.; Chiodin, Marta; Hoff, Katharina J.; Dessimoz, Christophe; Tomiczek, Bartlomiej; Schiffer, Philipp H.; Müller, Steven; Domman, Daryl; Horn, Matthias; Kuhl, Heiner; Timmermann, Bernd; Satoh, Noriyuki; Hikosaka-Katayama, Tomoe; Nakano, Hiroaki; Rowe, Matthew L.; Elphick, Maurice R.; Thomas-Chollier, Morgane; Hankeln, Thomas; Mertes, Florian; Wallberg, Andreas; Rast, Jonathan P.; Copley, Richard R.; Martinez, Pedro; Telford, Maximilian J. (2019). "Mitigating Anticipated Effects of Systematic Errors Supports Sister-Group Relationship between Xenacoelomorpha and Ambulacraria". Current Biology. 29 (11): 1818–1826.e6. Bibcode:2019CBio...29E1818P. doi:10.1016/j.cub.2019.04.009. hdl: 21.11116/0000-0004-DC4B-1 . ISSN   0960-9822. PMID   31104936. S2CID   155104811.
3. Marlétaz, Ferdinand (2019-06-17). "Zoology: Worming into the Origin of Bilaterians". Current Biology. 29 (12): R577 –R579. Bibcode:2019CBio...29.R577M. doi: 10.1016/j.cub.2019.05.006 . ISSN   0960-9822. PMID   31211978.
4. Kapli, Paschalia; Natsidis, Paschalis; Leite, Daniel J.; Fursman, Maximilian; Jeffrie, Nadia; Rahman, Imran A.; Philippe, Hervé; Copley, Richard R.; Telford, Maximilian J. (2021-03-19). "Lack of support for Deuterostomia prompts reinterpretation of the first Bilateria". Science Advances. 7 (12): eabe2741. Bibcode:2021SciA....7.2741K. doi:10.1126/sciadv.abe2741. ISSN   2375-2548. PMC   7978419 . PMID   33741592.
5. Robertson, Helen E.; Sebe-Pedros, Arnau; Saudemont, Baptiste; Loe Mie, Yann; Zakrzewski, Ann; Grau-Bové, Xavier; Mailhe, Marie-Pierre; Schiffer, Philipp; Telford, Maximilian J.; Marlow, Heather (2022-08-18). "Single cell atlas of Xenoturbella bocki highlights the limited cell-type complexity of a nonvertebrate deuterostome lineage". bioRxiv. doi:10.1101/2022.08.18.504214.