The cnidarian-bilaterian ancestor possessed at least 56 homeoboxes: evidence from the starlet sea anemone, Nematostella vectensis.

Background: Homeodomain transcription factors are key components in the developmental toolkits of animals. While this gene superclass predates the evolutionary split between animals, plants, and fungi, many homeobox genes appear unique to animals. The origin of particular homeobox genes may, therefore, be associated with the evolution of particular animal traits.