Platyzoa
| Platyzoa | |
|---|---|
 |
|
| Pseudobiceros bedfordi (Bedford's Flatworm) | |
| Scientific classification | |
| Kingdom: | Animalia |
| Subkingdom: | Eumetazoa |
| Clade: | Bilateria |
| Clade: | Nephrozoa |
| (unranked): | Protostomia |
| (unranked): | Spiralia |
| (unranked): |
Platyzoa Cavalier-Smith, 1998 |
| Phyla | |
|
|
The Platyzoa /ˌplætᵻˈzoʊ.ə/ are a group of protostome unsegmented animals proposed by Thomas Cavalier-Smith in 1998. Cavalier-Smith included in Platyzoa the phylum Platyhelminthes (or flatworms), and a new phylum, the Acanthognatha, into which he gathered several previously described phyla of microscopic animals. More recently it has been described as the Rouphozoa and the Gnathifera.
One current scheme places the following traditional phyla in Platyzoa:
None of the Platyzoa groups have a respiration or circulation system because of their small size, flat body or parasitic lifestyle. The Platyhelminthes and Gastrotricha are acoelomate. The other phyla have a pseudocoel, and share characteristics such as the structure of their jaws and pharynx, although these have been secondarily lost in the parasitic Acanthocephala. They form a monophyletic subgroup called the Gnathifera.
The name "Platyzoa" is used because most members are flat, though rotifers are not.
The Platyzoa are close relatives of the Lophotrochozoa. Together the two make up the Spiralia.
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