Placozoa

Placozoa are simple, multicellular animals that lack distinct tissues and organs. They are characterized by their flattened, changeable body shape and irregular movement. These organisms are considered to be at a cellular level of organization, meaning their cells specialize and coordinate their activities, but do not form complex tissues or organs like more advanced animals. Placozoans inhabit marine environments and their simplicity has been an adaptive advantage. They are distinct from protozoans, which are single-celled organisms, and from placoderms, which are an extinct group of primitive jawed fishes.123456