Linked from
The 9 pages that link to Choanoflagellate, each with the reason it gives.
SpongeCompared with: Its resemblance to sponge choanocytes offers clues, but it is not an animal.
ChoanocyteCompared with: Choanoflagellates resemble choanocytes in form, but are not sponge cells.
MulticellularityRelated: They illuminate traits that may have preceded animal multicellularity.
OpisthokontBroader topic: Choanoflagellates are close unicellular relatives of animals.
FilastereaRelated: They are another close unicellular relative of animals, alongside filastereans.