Monotypic animal genera

Salinella salve is a dubious species of a very simple animal which some have named as the sole member of the phylum Monoblastozoa. It was discovered in 1892 by Johannes Frenzel in the salt pans of Córdoba Province, Argentina and cultivated in a laboratory by him. This animal has not been found since and its real existence is considered as doubtful. A project involving Michael Schrödl from the Zoological State Collection in Munich searched for Salinella in salt lakes across Argentina and Chile, but failed to find any specimens.

Hoilungia is a genus that contains one of the simplest animals and belongs to the phylum Placozoa. Described in 2018, it has only one named species, H. hongkongensis, although there are possible other species. The animal superficially resembles another placozoan, Trichoplax adhaerens, but genetically distinct from it as mitochondrial DNA analysis revealed.