Parabasalidea

**Definition:** A group (or phylum) of flagellated, anaerobic EUKARYOTES that are endosymbionts of animals. They lack mitochondria but contain small energy-producing hydrogenosomes. The group is comprised of two major classes: HYPERMASTIGIA and TRICHOMONADIDA.

**Tree numbers:** - B01.630

**Synonyms:** - Parabasalia - Parabasalids