Planulozoa is a clade which includes the Placozoa, Cnidaria (corals and jellyfish) and the Bilateria (all the more complex animals including worms, insects and vertebrates).[2][3] The designation Planulozoa may be considered a synonym to Parahoxozoa. Within Planulozoa, the Placozoa may be a sister of Cnidaria to the exclusion of Bilateria.[4][5][6][7] The clade excludes basal animals such as the Ctenophora (comb jellies),[8][9][3] and Porifera (sponges).[10][11][12] Although this clade was sometimes used to specify a clade of Cnidaria and Bilateria to the exclusion of Placozoa (against the original intention of its proposal), this is no longer favoured due to recent data indicating a sister group relationship between Cnidaria and Placozoa.[13]
The phylogenetic tree indicates approximately how many millions of years ago (mya) the lineages split. Here, Planulozoa is shown sans Placozoa.[14][15][16]
Planulozoa are associated with the emergence of the Zoc and ZF-NC gene domains.[17]
^Schuchert, Peter (1993-03-01). "Trichoplax adhaerens (Phylum Placozoa) has Cells that React with Antibodies Against the Neuropeptide RFamide". Acta Zoologica. 74 (2): 115–117. doi:10.1111/j.1463-6395.1993.tb01227.x.
^Syed, Tareq; Schierwater, Bernd (2002-06-01). "The evolution of the placozoa: A new morphological model". Senckenbergiana Lethaea. 82 (1): 315–324. doi:10.1007/bf03043791. ISSN0037-2110. S2CID16870420.