An assemblage of eukaryotic protists characterized by one or more feeding grooves equipped with flagella that propel food to the mouth. They include, among others, the diplomonads (e.g. Giardia, responsible for giardiasis in humans), other gut parasites or symbionts (retortamonads and oxymonads), trichomonads (such as the human vaginal parasite Trichomonas), the jakobids (a group of zoomastigotes), and the discicristates (euglenids, diplomonads, amoebomastigotes, etc.). Molecular systematics reveals that excavates could be a very early eukaryote lineage, a view supported by their simplified organelles and by the fact that the jakobids have mitochondrial genomes that are remarkably similar to those of bacteria, attesting to the ancient origin of mitochondria as intracellular symbiotic bacteria.