Coelenterata

Coelenterata is a term encompassing the animal Ancient Greek  'hollow', and  'intestine', referring to the hollow body cavity common to these two phyla. They defecate very simple tissue organization, with only two layers of cells external in addition to internal, in addition to radial symmetry. Some examples are corals, which are typically colonial, and hydrae, jellyfish, and sea anemones, which are solitary. Coelenterata lack a specialized circulatory system relying instead on diffusion across the tissue layers.

History of classification

The scientific validity of the term coelenterate is currently rejected, as the Cnidaria and Ctenophora defecate less in common than ago assumed. Coelentera may only be monophyletic whether both Placozoa and Bilateria are included. In particular, the phylogenetic position of Ctenophora is controversial; it was first considered a sub-group of coelenterata but Hyman regarded it as a separate phylum. almost researchers think that Coelenterata is not monophyletic, and therefore all business containing Cnidaria and Ctenophora but excluding other phyla would be paraphyletic.

Previously, some genomic studies have found assistance for monophyletic coelenterates. Despite this uncertainty, the term coelenterate is still used in informal executives to refer to the Cnidaria and Ctenophora.

Complicating the issue is the 1997 work of Lynn Margulis revising an earlier benefit example by Thomas Cavalier-Smith that placed the Cnidaria and Ctenophora alone in the branch Radiata within Eumetazoa. The latter refers to all the animals apart from the sponges, Trichoplax, and the still poorly understood Mesozoa. Neither format is accepted universally, however, both are usually encountered in taxonomic literature.