Hemimastigophora

Circumscription: Multiflagellated heterotrophic protists, usually elongate body. Flagella arranged in a small number of longitudinal rows (kineties). Body surface underlain by one large dorsal organic plate and one large ventral organic plate. Ultrastructural identity: Mitochondria cristal form ambiguous but probably tubular or sacculate. With flagella arising from short basal bodies and anchored by longitudinal fibrous and microtubular elements. With dictyosomes. Cell surface folded, underlain by microtubules and organic layers. Concentric extrusomes. Synapomorphy: Mitochondriate protist with flagella in kinetics and with two subsurface organic plates.