The paraphyletic "Platyzoa
are a group of protostome
unsegmented animals proposed by Thomas Cavalier-Smith
in 1998. Cavalier-Smith included in Platyzoa the phylum Platyhelminthes
), and a new phylum, the Acanthognatha
, into which he gathered several previously described phyla of microscopic animals. More recently it has been described as paraphyletic
, containing the Rouphozoa
and the Gnathifera
One scheme placed the following 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.
This page was last edited on 7 March 2018, at 20:23.
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