Kingdom Animalia-Acoelomates (Diagram)

Acoelomate are believed to evolve from cyanoflagellates (a protozoa with single flagellum surrounded by a collar of microvilli). It can be divided to different phylum and classes as indicate in the diagram below.

As indicate in the diagram, some have their own class and some do not. For example Flatworm (Phylum Plathelminthes) has three different classes but Comb Jellies (Phylum Ctenophora) do not. But don’t know whether some day biologist will come up with a new class for this jellies.