Systematic Study on Nematoda Phylum,Gastrotricha Phylum and Rotifera Phylum

This paper analyses the systematics between Nematoda phyllum,Gastrotricha phylum and Rotifera phylum by cladistics method. The conclusion is that these three parts belong to a monophyletic group,in which Gastrotricha phylum and Rotifera phylum are a sister group. Then,Nematoda Phylum is another branch which was earlier differentiated from the common ancestor of these three parts. For these reason, we think that these three parts should be merged into a new phylum, namely Syncytia. The original each phylum should be demoted separately:Nematoda class,Gastrotricha class and Rotifera class.Protocoelomata phylum this category should be discarded.