Description of Heterolobosea:
Circumscription: Heterotrophic amoebas, amoebo-flagellates (collectively the vahlkampfiids or schizopyrenids), flagellates (Percolomonas), and slime moulds (the acrasids). Two genera have no flagellated stage, but the majority of species have the capacity to convert from amoebas to flagellates or to encyst. Flagellates have two to four flagella and usually an ingestion region with an adjacent ridge supported by microtubules. Amoebas move with eruptive pseudopodia. Common in soils, but the group contains a facultative pathogen of the human central nervous systems (Naegleria). The acrasid slime moulds are one of two types of cellular slime moulds in which resistant spores are released from an aggregated mass of cells and in which differentiation may occur. Ultrastructural identity: Mitochondrial cristae discoidal (i.e., with pedicel) or sacculate, mitochondria may be partly enclosed by an extension of endoplasmic reticulum. Basal bodies parallel or nearly so, giving rise to several microtubular roots and sometimes a cross-striated nonmicrotubular root. Without dictyosomes with stacks of sacs, usually no extrusomes, cell surface naked. Nuclear envelope intact during mitosis, spindle microtubules internal. Synapomorphy: To be resolved but either discieristate protists forming eruptive pseudopodia or discicristate protists with parallel basal bodies inserting on an electrondense pad, possibly with a substantial cross-striated root.