Description of Parabasalids:
Circumscription: Mostly flagellated protozoa, mostly commensals in insects or parasites. Some (hypermastigids) may have very large numbers of flagella and are usually symbionts in the intestines of wood-eating insects, others (trichomonads) may have an undulating membrane. An axostyle may be visible. A few species are free living. Ultrastructural identity: No mitochondria. All cells (excepting aflagellated taxa) with at least one cluster of four basal bodies, which are the source of microtubular roots. Dictyosomes are well developed, often numerous, and may be associated with a nonmicrotubular rootlet, the parabasal fibre. Cell surface naked, no extrusomes. Mitosis with intact nuclear envelope and with spindle microtubules lying external to the nucleus. Synapomorphy: Flagellated protists with a parabasal apparatus of dictyosomes anchored to a striated root.