[1] Three groups are currently assigned to the clade Filozoa: From Latin filum meaning "thread" and Greek zōion meaning "animal".

A phylogenetic tree of Filozoa and its most closely related clades:[2][3][4][5] Fonticulida Nucleariida

Rozella Namako-37 Microsporidia Ichthyosporea Syssomonas Corallochytrium Filasterea Choanoflagellatea Animalia The ancestral opisthokont cell is assumed to have possessed slender filose (thread-like) projections or 'tentacles'.

They are retained in Filozoa, where they are simple and non-tapering, with a rigid core of actin bundles (contrasting with the flexible, tapering and branched filopodia of nucleariids and the branched rhizoids and hyphae of fungi).

In choanoflagellates and in the most primitive animals, namely sponges, they aggregate into a filter-feeding collar (made from microvilli, that are also made from actin) around the cilium or flagellum; this is thought to be an inheritance from their most recent common filozoan ancestor.