nephrozoa

{{Automatic taxobox

| fossil_range = Ediacaran - Present, {{fossilrange|558|0}}

| image = File:Nephrozoa collage.png|220px

rect 1 1 400 300 Echinodermata

rect 400 1 800 300 Chordata

rect 1 300 400 600 Ecdysozoa

rect 400 300 800 600 Hemichordata

rect 1 600 400 900 Lophotrochozoa

rect 400 600 800 900 Platyzoa

| display_parents = 3

| taxon = Nephrozoa

| authority = Jondelius et al., 2002

| subdivision_ranks = Subdivisions

| subdivision = * †Ikaria

| synonyms = Eubilateria Ax, 1987

}}

Nephrozoa is a proposed major clade of bilaterian animals. Under this hypothesis, Xenacoelomorpha forms the earliest diverging branch of Bilateria, with all other bilaterians placed in Nephrozoa. It contrasts with the Xenambulacraria hypothesis, which instead posits that Xenacoelomorpha is most closely related to Ambulacraria (usually placed as deuterostomes).{{cite journal |last1=Philippe |first1=Hervé |last2=Poustka |first2=Albert J. |last3=Chiodin |first3=Marta |last4=Hoff |first4=Katharina J. |last5=Dessimoz |first5=Christophe |last6=Tomiczek |first6=Bartlomiej |last7=Schiffer |first7=Philipp H. |display-authors=etal |year=2019 |title=Mitigating Anticipated Effects of Systematic Errors Supports Sister-Group Relationship between Xenacoelomorpha and Ambulacraria |journal=Current Biology |volume=29 |issue=11 |pages=1818–1826.e6 |doi=10.1016/j.cub.2019.04.009 |issn=0960-9822 |pmid=31104936 |bibcode=2019CBio...29E1818P |s2cid=155104811 |hdl-access=free |hdl=21.11116/0000-0004-DC4B-1}}{{Cite journal |last=Marlétaz |first=Ferdinand |date=2019-06-17 |title=Zoology: Worming into the Origin of Bilaterians |journal=Current Biology |volume=29 |issue=12 |pages=R577–R579 |doi=10.1016/j.cub.2019.05.006 |issn=0960-9822 |pmid=31211978 |doi-access=free|bibcode=2019CBio...29.R577M }}{{cite journal |last1=Kapli |first1=Paschalia |last2=Telford |first2=Maximilian J. |date=11 Dec 2020 |title=Topology-dependent asymmetry in systematic errors affects phylogenetic placement of Ctenophora and Xenacoelomorpha |journal=Science Advances |volume=6 |issue=10 |pages=eabc5162 |doi=10.1126/sciadv.abc5162 |pmc=7732190 |pmid=33310849 |doi-access=free|bibcode=2020SciA....6.5162K }}{{Cite journal |last1=Kapli |first1=Paschalia |last2=Natsidis |first2=Paschalis |last3=Leite |first3=Daniel J. |last4=Fursman |first4=Maximilian |last5=Jeffrie |first5=Nadia |last6=Rahman |first6=Imran A. |last7=Philippe |first7=Hervé |last8=Copley |first8=Richard R. |last9=Telford |first9=Maximilian J. |date=2021-03-19 |title=Lack of support for Deuterostomia prompts reinterpretation of the first Bilateria |journal=Science Advances |volume=7 |issue=12 |pages=eabe2741 |bibcode=2021SciA....7.2741K |doi=10.1126/sciadv.abe2741 |pmc=7978419 |pmid=33741592}}{{Cite journal |last1=Marlétaz |first1=Ferdinand |last2=Peijnenburg |first2=Katja T.C.A. |last3=Goto |first3=Taichiro |last4=Satoh |first4=Noriyuki |last5=Rokhsar |first5=Daniel S. |date=2019-01-21 |title=A New Spiralian Phylogeny Places the Enigmatic Arrow Worms among Gnathiferans |journal=Current Biology |volume=29 |issue=2 |pages=312–318.e3 |doi=10.1016/j.cub.2018.11.042 |pmid=30639106 |doi-access=free|bibcode=2019CBio...29E.312M }}{{Cite journal |last1=Schiffer |first1=Philipp H |last2=Natsidis |first2=Paschalis |last3=Leite |first3=Daniel J |last4=Robertson |first4=Helen E |last5=Lapraz |first5=François |last6=Marlétaz |first6=Ferdinand |last7=Fromm |first7=Bastian |last8=Baudry |first8=Liam |last9=Simpson |first9=Fraser |last10=Høye |first10=Eirik |last11=Zakrzewski |first11=Anne C |last12=Kapli |first12=Paschalia |last13=Hoff |first13=Katharina J |last14=Müller |first14=Steven |last15=Marbouty |first15=Martial |date=2024-08-07 |title=Insights into early animal evolution from the genome of the xenacoelomorph worm Xenoturbella bocki |journal=eLife |language=en |volume=13 |doi=10.7554/eLife.94948 |doi-access=free |issn=2050-084X |pmc=11521371 |pmid=39109482}} Which hypothesis is correct has been debated, and as of 2024 the issue is unresolved.{{Cite journal |last1=Abalde |first1=Samuel |last2=Jondelius |first2=Ulf |date=2025-02-10 |editor-last=Whelan |editor-first=Nathan |title=A Phylogenomic Backbone for Acoelomorpha Inferred From Transcriptomic Data |url=https://academic.oup.com/sysbio/article/74/1/70/7841810 |journal=Systematic Biology |language=en |volume=74 |issue=1 |pages=70–85 |doi=10.1093/sysbio/syae057 |issn=1063-5157 |pmc=11809588 |pmid=39451056}}{{Cite journal |last1=Robertson |first1=Helen E. |last2=Sebé-Pedrós |first2=Arnau |last3=Saudemont |first3=Baptiste |last4=Loe-Mie |first4=Yann |last5=Zakrzewski |first5=Anne-C. |last6=Grau-Bové |first6=Xavier |last7=Mailhe |first7=Marie-Pierre |last8=Schiffer |first8=Philipp |last9=Telford |first9=Maximilian J. |last10=Marlow |first10=Heather |date=2024-03-19 |title=Single cell atlas of Xenoturbella bocki highlights limited cell-type complexity |journal=Nature Communications |language=en |volume=15 |issue=1 |page=2469 |doi=10.1038/s41467-024-45956-y |issn=2041-1723 |pmc=10951248 |pmid=38503762|bibcode=2024NatCo..15.2469R }} The clade is named after a key synapomorphy of the group: the presence of specialized excretory organs known as nephridia.{{Cite journal |last=Jondelius |first=Ulf |last2=Ruiz-Trillo |first2=Iñaki |last3=Baguñà |first3=Jaume |last4=Riutort |first4=Marta |date=2002 |title=The Nemertodermatida are basal bilaterians and not members of the Platyhelminthes |url=https://onlinelibrary.wiley.com/doi/10.1046/j.1463-6409.2002.00090.x |journal=Zoologica Scripta |language=en |volume=31 |issue=2 |pages=201–215 |doi=10.1046/j.1463-6409.2002.00090.x |issn=1463-6409|url-access=subscription }}