Nephrozoa is a proposed major
clade
In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...
of
bilateria
Bilateria () is a large clade of animals characterised by bilateral symmetry during embryonic development. This means their body plans are laid around a longitudinal axis with a front (or "head") and a rear (or "tail") end, as well as a left†...
n
animal
Animals are multicellular, eukaryotic organisms in the Biology, biological Kingdom (biology), kingdom Animalia (). With few exceptions, animals heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, ...
s. 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).
Which hypothesis is correct has been debated, and as of 2024 the issue is unresolved. The clade is named after a key synapomorphy of the group: the presence of specialized excretory organs known as
nephridia.
Below is a proposed
phylogenetic tree
A phylogenetic tree or phylogeny is a graphical representation which shows the evolutionary history between a set of species or taxa during a specific time.Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA. In ...
of Nephrozoa:
References
Further reading
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External links
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Bilaterians
Ediacaran first appearances
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