Nucleariida is a group of amoebae with filose pseudopods, known mostly from soils and freshwater. They are distinguished from the superficially similar vampyrellids mainly by having mitochondria with discoid cristae.
Nucleariids are opisthokonts, the group which includes animals, fungi and several smaller groups. Several studies place the nucleariids as a sister group to the fungi.
The genera Rabdiophrys, Pinaciophora, and Pompholyxophrys, freshwater forms with hollow siliceous scales or spines, were formerly included in Nucleariida, but are now placed in Rhizaria. In the past, nucleariids were included among the heliozoa as the Rotosphaerida.
According to a 2009 paper, Fonticula, a cellular slime mold, is an opisthokont and more closely related to Nuclearia than to fungi.
Order Nucleariida Cavalier-Smith 1993
Family Nucleariidae Cann & Page 1979
Genus Nuclearia Cienkowski 1865 [Astrodisculus Greeff 1869; Nuclearella Frenzel 1897; Nuclearina Frenzel 1897; Heliosphaerium Frenzel 1897; Nucleosphaerium Cann & Page 1979]
Species Astrodisculus minutus Greeff 1869
Species Astrodisculus araneiformis Schewiakoff 1893
Species Astrodisculus laciniatus Penard 1904 [Chlamydaster lacinatus (Penard 1904) Rainer 1968]
Species Astrodisculus affinis Schouteden 1905
Species Astrodisculus marinus Kufferath 1952
Species N. conspicua West 1903
Species N. lohmanni Kufferath 1952
Species N. delicatula Cienkowski 1865
Species N. flavescens (Greef 1869) Patterson 1984 [Astrodisculus flavescens Greeff 1869]
Species N. flavocapsulata (Greef 1869) Patterson 1984 [Astrodisculus flavocapsulata Greeff 1869; Astrodisculus penari Roskin 1929; Astrodisculus serratus Walton 1930; Heliosphaerium polyedricum Frenzel 1897]
Species N. leuckarti (Frenzel 1897) Patterson 1984 [Nuclearina leuckarti Frenzel 1897]
Species N. moebiusi Frenzel 1897
Species N. pattersoni Dyková et al. 2003
Species N. polypodia Schewiakoff 1863
Species N. radians (Greef 1869) Patterson 1984 [Astrodisculus radians Greeff 1869 sensu Penard 1904 non Stern 1924; Nucleosphaerium radians (Greef 1869); Nucleosphaerium tuckeri Cann & Page 1979; Heliosphaerium aster Frenzel 1897; Heliophrys varians West]
Species N. simplex Cienkowsky 1865 [Nuclearella variabilis Frenzel 1897]
Species N. thermophila Yoshida, Nakayama & Inouye 2009
Species N. rubra (Greef 1869) Patterson 1984 [Astrodisculus rubra Greeff 1869; Astrodisculus zonatus Penard 1904; Nuclearia caulescens Penard 1903: pro parte; Nuclearia zonatus (Penard 1904) Siemensma 1981]
Nucleariids (Nuclearia and Micronuclearia) are usually small, up to about 50 μm in size.
