Monoblastozoa was granted the title of phylum after the recognition that Mesozoa was too diverse to be a phylum unto itself.
Only one species has been described, Salinella salve. It was discovered in 1892 by J. Frenzel in the salt pans of Argentina and cultivated in laboratory by him. This animal has not been found since and its real existence is considered as doubtful. More organized than Protozoa, but still very primitive multicellular organisms.
Characterised by their distinct anterior/posterior parts and being densely ciliated, especially around "mouth" and "anus". They only have one layer of cells. They reproduce asexually by transverse fission of body. Although sexual reproduction was suspected, no evidence exists of it. Michael Schrödl from the Zoological State Collection in Munich is involved in a project to search for Salinella in Argentina.