Placozoa
The Placozoa are a basal form of free-living (non-parasitic) multicellular organism. They are the simplest in structure of all animals. Three genera have been found: the classical Trichoplax adhaerens, Hoilungia hongkongensis, and Polyplacotoma mediterranea, where the last appears most basal. The last two have been found only since 2017. Although the Placozoa were first discovered in 1883 by the German zoologist, Franz Eilhard Schulze (1840–1921) and since the 1970s more systematically analyzed by the German protozoologist, Karl Gottlieb Grell (1912–1994), a common name does not yet exist for the taxon; the scientific name means "flat animals".
Placozoa-1