Nephrozoa

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).^{[1][2][3][4][5][6]} Which hypothesis is correct has been debated, and as of 2024 the issue is unresolved.^[7][8] The clade is named after a key synapomorphy of the group: the presence of specialized excretory organs known as nephridia.^[9]

Nephrozoa Temporal range: Ediacaran - Present, 558–0 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Subkingdom:	Eumetazoa
Clade:	ParaHoxozoa
Clade:	Bilateria
Clade:	Nephrozoa Jondelius et al., 2002
Subdivisions
†Ikaria Deuterostomia Chordata Ambulacraria Protostomia Ecdysozoa Spiralia
Synonyms
Eubilateria Ax, 1987

Below is a proposed phylogenetic tree of Nephrozoa:

Bilateria	Xenacoelomorpha Nephrozoa Deuterostomia Chordata 540 mya Ambulacraria Echinodermata Hemichordata anus before mouth Protostomia Ecdysozoa Spiralia 610 mya 650 mya