Placozoa | |
---|---|
Scientific classification | |
Kingdom: | |
Subkingdom: | |
Phylum: | Placozoa |
The Placozoa are an animal phylum, a primitive form of invertebrate. They are the simplest in structure of all metazoa.
The Placozoa is usually considered to have only one species, Trichoplax adhaerens, but there is enough genetic diversity that it is possible that there are multiple, morphologically similar species.
Although they were first discovered in 1883, a common name does not exist for the taxon. The scientific name literally means "flat animals".
Trichoplax is a small, flattened, animal around a millimetre across. Like an Amoeba, it has no regular outline, although the upper surface is always flattened. The body consists of an outer layer of simple epithelium enclosing a loose sheet of cells. The epithelial cells bear flagella, which the animal uses to help it creep along the seafloor. Between these layers is the fiber syncytium, a liquid-filled cavity strutted open by star-like fibers.