Description of Phalansterium

Circumscription: Heterotrophic flagellates, forming colonies with cells embedded in an organic globular matrix, a single apical flagellum with tight-fitting continuous cytoplasmic collar. Ultrastructural identity: Mitochondria with tubular cristae, cells with a single apical flagellum with single basal body, anchorage involving concentric rings, which give rise to radiating microtubules. Well-developed dictyosomes associated with basal body. Flagellum with mucus but otherwise without hairs, scales, or other excrescences, no paraxonemal rods. Synapomorphy: Tubulocristate protist with single apical flagellum anchored by a radially symmetrical array of microtubules. Composition: One genus, several species.