were first divided in five clades in 2004 based on their 16S mitochondrial genome. Clade III was later included in the genus Hoilungia.

In 2022, as part of a wider formalization of placozoan taxonomy, Cladtertia was erected to encompass lineages previously placed in Clade III, with Cladtertia collaboinventa as its type species. It is the only described genus in the family Cladtertiidae, which is sister to Hoilungidae in