Description of Nucleariids:
Circumscription: Amoeboid organisms, with fine pseudopodia unsupported by microtubules, with or without hollow siliceous plates or spheres or spines, the walls of which are a meshwork. Uninucleate or multinucleate. No flagellated stages known. Mostly described from soils or freshwater. Ultrastructural identity: Mitochondria with discoidal cristae. With dictyosomes. Pseudopodia without microtubules, supported by microfibrillar material. During mitosis, the nuclear envelope remains intact and microtubules lie within the nucleus. One species reported with a microfibrillar cytoskeletal sheath. No extrusomes. Synapomorphy: None known, distinguished at this time as filose amoebas with discoid mitochondrial cristae.