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 (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 paraphyletic, containing the rouphozoa and the gnathifera.