Hyalospheniidae

There has been several attempts at classifying Hyalospheniidae among testate amoebae, as well as its internal classification. American paleontologist Joseph Leidy, in 1874, was possibly the first to notice common characteristics between the cells. He described the vase-shaped tests as composed of small siliceous particles ("discoid plates and minute rods") caught within an organic matrix, interpreted to be originated by the amoeba ("intrinsic"). He grouped those species within the genus Nebela, restricting them from the previously known genus of testate amoebae Difflugia. Instead, he described Difflugia species as having a "test composed of extraneous bodies, such as particles of quartzose sand, and diatom cases".[13][6]

In 1877, German zoologist Franz Eilhard Schulze described the families Hyalosphenidae, Arcellidae, Quadrulidae and Difflugidae. Amoebae with an organic homogenous test such as Hyalosphenia were placed in Hyalospheniidiae, while Nebela was placed in Difflugidae, and Quadrulella in Quadrulidae.[2][6]

In 1882, Taranek described the family Nebelidae to include amoebae with siliceous plates: Nebela, Lesquereusia, Quadrulella, Corythion (which was later excluded), Amphizonella, Cochliopodium, Hyalosphenia, Leptochlamys and Zonomyxa.[5] This family was redefined later in 1942 by Jung and organized into thirteen genera newly described by him: Alocodera, Apodera, Argynnia, Deflandria, Nebela, Leidyella, Penardiella, Physochila, Porosia, Pterygia, Quadrulella, Schaudinnia and Umbonaria.[14] However, Jung did not designate type species in his classification, which invalidated all genera with more than one species.[lower-alpha 1] Consequently, only monotypic genera such as Alocodera, Physochila and Porosia were recognized, and the remaining genera were absorbed by Nebela. Later, by assigning types, micropaleontologists Loeblich and Tappan validated Apodera and Certesella in 1961,[16] and Vucetich validated Argynnia in 1974.[17]

In 2002, German protozoologist Ralf Meisterfeld wrote the last review of the family based exclusively on morphological characters. He reclassified Nebela and similar genera into two families: Hyalospheniidae, composed of genera with rigid, chitinoid, organic tests (Hyalosphenia and Leptochlamys); and Nebelidae, composed of genera with tests constructed from plates of small euglyphids or diatom fragments (Apodera, Argynnia, Certesella, Nebela, Physochila, Porosia, Schoenbornia). Following a 1979 classification,[18] he excluded the genus Quadrulella into the family Lesquereusiidae along with other arcellinid genera with self-secreted siliceous rods in their tests.[19][6]

The first phylogenetic analyses of Arcellinida based on molecular data demonstrated that Nebela and Nebelidae were not monophyletic, i.e. did not form a clade or group of taxa evolved from a common ancestor without including other genera from Hyalospheniidae.[20] Species of Apodera, Porosia, Nebela and Hyalosphenia were intermingled with each other in a clade known as "core Nebelas".[7] Because of this result, and presence of distinguishing Hyalospheniidae traits within some Nebelidae, the two families were synonymised under the first name.[3] In addition, many species of the polyphyletic Nebela were separated into new monophyletic genera, namely Padaungiella in 2012,[3] Cornutheca, Gibbocarina, Longinebela, Mrabella and Planocarina in 2016,[21] and finally Alabasta in 2018.[22]

The following cladogram illustrates the evolutionary relationships between all hyalospheniid genera found through a 2018 phylogenetic analysis,[22] with the exception of Porosia, a genus excluded from the analysis that appears to be closely related to Certesella[23] and is therefore placed next to it in the cladogram. Another genus excluded by the same analysis is Apodera, which is the sister group to a clade containing Alocodera and Padaungiella, according to a 2021 phylogeny.[24]

The current taxonomy of the family recognizes 14 genera,[1][25] with a total of 78 species:

• Alabasta Duckert, Blandenier, Kosakyan & Singer 2018 — 3 species.[22]

• Alocodera Jung, 1942[26] — 1 species.[27]

• Apodera Loeblich & Tappan, 1961 — 4 species.[6][28]

• Certesella Loeblich & Tappan, 1961 — 5 species.[29][30]

• Cornutheca Kosakyan, Lahr, Mulot, Meisterfeld, Mitchell & Lara, 2016 — 3 species.[21]

• Gibbocarina Kosakyan, Lahr, Mulot, Meisterfeld, Mitchell & Lara, 2016 — 3 species.[21][31]

• Hyalosphenia (Stein, 1857) Schulze, 1877 — 17 species.[6]

• Longinebela Kosakyan, Lahr, Mulot, Meisterfeld, Mitchell & Lara, 2016 — 5 species.[21][32]

• Mrabella Kosakyan, Lahr, Mulot, Meisterfeld, Mitchell & Lara, 2016 — 2 species.[21]

• Nebela Leidy, 1874 em. Kosakyan, Lahr, Mulot, Meisterfeld, Mitchell & Lara, 2016 — 13 species.[21]

• Padaungiella Lara et Todorov, 2012 — 5 species.[3]

• Planocarina Kosakyan, Lahr, Mulot, Meisterfeld, Mitchell & Lara, 2016 — 4 species.[21]

• Porosia Jung, 1942[26] — 2 species.[23]

• Quadrulella Cockerell, 1909 em. Kosakyan, Lahr, Mulot, Meisterfeld, Mitchell & Lara, 2016 — 11 species.[21]