Order Arcellinida Kent 1880 Diagnosis: Cell covered with hard or highly rigid organic or mineral extracellular test consisting of either self-secreted elements (calcareous, siliceous or chitinoid), a sheet-like chitinoid structure, or recycled organic or mineral particles bound together, with a single main opening. Remarks: Arcellinida comprises all testate amoebae with lobose pseudopodia. It is the largest group of testate amoebae with 687 nominal species (Kosakyan et al, 2016). However, the major part of these species needs comprehensive nomenclature and taxonomic revision. Arcellinida exhibit a wide array of the test shapes composed of different material, which was the key characteristic for their classification. Meisterfeld (2000) organized them into three suborders: Arcellina, Difflugina and Phryganellina. Recent molecular investigations has challenged the system, and the positions of many species and genera were switched between families. These molecular reconstructions have demonstrated the limitations of the use of test composition as a classification character. A number of modifications were made on high as well as low-taxonomic levels. Higher-level taxonomy of Arcellinida is uncertain, while lower-level taxonomy is constantly changing (Kosakyan et al, 2016; Gomaa et al., 2017). Further reading: Kosakyan et al. (2016): Current and future perspectives on the systematics, taxonomy and nomenclature of testate amoebae – European Journal of Protistology Gomaa et al. (2017): A contribution to the phylogeny of agglutinating Arcellinida (Amoebozoa) based on SSU rRNA gene sequences – European Journal of Protistology 59: 99-107
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Difflugia australis

D. australis after Playfair, 1917 Difflugia australis (Playfair, 1917) Gauthier-Lièvre et Thomas, 1958 Syn.: Difflugia bacillariarum var. australis Playfair 1917 Diagnosis: Test broadly ovate, with

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Difflugia baradlana

D. baradlana after Varga, 1963 Difflugia baradlana Varga, 1963 Diagnosis: Test ovoid with a very small neck which is about 1/4 of the test length.

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Difflugia angelica

D. angelica after Gauthier-Lièvre et Thomas, 1960 Difflugia angelica Gauthier-Lièvre et Thomas, 1960 Diagnosis: Test spherical, slightly mammillated. Pseudostome regularly lobed like a star with

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Difflugia algaephila

D. algaephila after Decloitre, 1977 (l) and Chardez (1980) Difflugia algaephila Decloitre, 1977 Diagnosis: Test ovoid, neatly pointed, with oblique round pseudostome. Dimensions: Length 73-75

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Difflugia key spherical

Spherical tests Tests that are more or less spherical, some with a collar, but all without spines or other outgrowths. The aperture or pseudostome is

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Difflugia key compressed

Compressed tests Compressed tests are more or less oval or elliptical in cross-section. The aperture is round or oval or even lobed. This group has no

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