Nephrozoa

Nephrozoa is a major clade of bilaterians, divided into the protostomes and the deuterostomes, containing almost all animal phyla and over a million extant species. Its sister clade is the Xenacoelomorpha. The Ambulacraria (conventionally deuterostomes) was formerly^{[dubious – discuss]} thought to be sister to the Xenacoelomorpha, forming the Xenambulacraria as basal Deuterostomes, or basal Bilateria invalidating Nephrozoa and Deuterostomes in earlier studies.[1][2][3] The coelom, the digestive tract and excretory organs (nephridia), and nerve cords developed in the Nephrozoa.[4] It has been argued that, because protonephridia are only found in protostomes, they cannot be considered a synapomorphy of this group. This would make Nephrozoa an improper name, leaving Eubilateria as this clade's name.[5]

Quick facts: Nephrozoa Temporal range Ediacaran - Present... ▼

Nephrozoa Temporal range: Ediacaran - Present, 558–0 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Diversity of nephrozoans
Scientific classification
Kingdom:	Animalia
Subkingdom:	Eumetazoa
Clade:	ParaHoxozoa
Clade:	Bilateria
Clade:	Nephrozoa Jondelius et al. , 2002
Phyla
Ikaria † Superphylum Deuterostomia Chordata Ambulacraria Hemichordata Echinodermata Protostomia (unranked) Superphylum Ecdysozoa Kinorhyncha Loricifera Priapulida Nematoda Nematomorpha Onychophora Tardigrada Arthropoda Spiralia (unranked) Superphylum Platyzoa Platyhelminthes Gastrotricha Chaetognatha Rotifera Acanthocephala Gnathostomulida Micrognathozoa Cycliophora Superphylum Lophotrochozoa Hyolitha † Nemertea Phoronida Bryozoa Entoprocta Brachiopoda Mollusca Annelida
Synonyms
Eubilateria Peter Ax, 1987

Chordates (which include all the vertebrates) are deuterostomes.[6] It seems very likely that the 555 million year old Kimberella was a protostome.[7][8] If so, this means that the protostome and deuterostome lineages must have split some time before Kimberella appeared — at least 558 million years ago, and hence well before the start of the Cambrian 538.8 million years ago.[6]