Planulozoa is a
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 ...
which includes the
Placozoa
Placozoa ( ; ) is a phylum of free-living (non-parasitic) marine invertebrates. They are blob-like animals composed of aggregations of cells. Moving in water by ciliary motion, eating food by Phagocytosis, engulfment, reproducing by Fission (biol ...
,
Cnidaria
Cnidaria ( ) is a phylum under kingdom Animalia containing over 11,000 species of aquatic invertebrates found both in fresh water, freshwater and marine environments (predominantly the latter), including jellyfish, hydroid (zoology), hydroids, ...
(corals and jellyfish) and the
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†...
(all the more complex animals including worms, insects and vertebrates).
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.
The clade excludes
basal animals such as the
Ctenophora (comb jellies),
and
Porifera
Sponges or sea sponges are primarily marine invertebrates of the animal phylum Porifera (; meaning 'pore bearer'), a Basal (phylogenetics) , basal clade and a sister taxon of the Eumetazoa , diploblasts. They are sessility (motility) , sessile ...
(sponges).
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 (several 2018 studies) indicating a sister group relationship between Cnidaria and Placozoa. However, a 2023 study supports Placozoa as sister to Cnidaria+Bilateria in several analyses.
The
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 ...
indicates approximately how many millions of years ago () the lineages split. Here, Planulozoa is shown sans Placozoa.
Planulozoa are associated with the emergence of the Zoc and ZF-NC gene domains.
References
{{Taxonbar, from=Q3180528
Animal unranked clades