Filozoa. Holozoa. Holozoa is a group of organisms that includes animals and their closest single-celled relatives, but excludes fungi.[1][2][3] [4] Holozoa is also an old name for the tunicate genus Distaplia.[5] Because Holozoa is a clade including all organisms more closely related to animals than to fungi, some authors prefer it to recognizing paraphyletic groups such as Choanozoa, which mostly consists of Holozoa minus animals.[6] Perhaps the best-known holozoans, apart from animals, are the choanoflagellates, which strongly resemble the collar cells of sponges, and so were theorized to be related to sponges even in the 19th century.
Proterospongia is an example of a colonial choanoflagellate that may shed light on the origin of sponges.