Belongs within: Allogromiida.
The Lagynidae are a group of Foraminifera with membranous or pseudochitinous tests. They have been distinguished from the similar Allogromiidae by the production of biflagellate gametes (Loeblich & Tappan 1964).
Characters (Loeblich & Tappan 1964): Test small, membranous to pseudochitinous, may have ferruginous encrustations or rarely agglutinated matter; may form colonies; aperture single, or numerous apertures not localised; gametes (where known) biflagellate.
<==Lagynidae (see below for synonymy)
|--Marenda Nyholm 1951G86
| `--*M. nematoides Nyholm 1951LT64
|--Schultzella Rhumbler 1904 [=Arschultzellum Rhumbler 1913, Schultzia Gruber 1888 nec Grimm 1876 nec Graff 1882]LT64
| `--*S. diffluens (Gruber 1884) [=Lieberkuehnia diffluens, *Arschultzellum diffluens, *Schultzia diffluens]LT64
|--Myxotheca Schaudinn 1893 [=Armyxothecum Rhumbler 1913]LT64
| `--*M. arenilega Schaudinn 1893 [=*Armyxothecum arenilegum]LT64
|--Boderia Wright 1867 [=Arboderium Rhumbler 1913]LT64
| `--*B. turneri Wright 1867 [=*Arboderium turneri]LT64
|--Echinogromia Schröder 1907 [=Arechinogromium Rhumbler 1913]LT64
| `--*E. multifenestrata Schröder 1907 [=*Arechinogromium multifenestratum]LT64
|--Heterogromia De Saedeleer 1934LT64
| `--*H. intermedia De Saedeleer 1934LT64
|--Ophiotuba Rhumbler 1894 [=Arophiotubum Rhumbler 1913]LT64
| `--*O. gelatinosa Rhumbler 1894 [=*Arophiotubum gelatinosum]LT64
|--Pseudoditrema Deflandre 1953K14
| `--*P. mikrous (De Saedeleer 1934) [=Ditrema mikrous]LT64
|--Rhumblerinella Schmidt 1929LT64
| `--*R. bacillifera Schmidt 1929LT64
|--Plagiophrys Claparède & Lachmann 1859 [=Arplagiophrum Rhumbler 1913]LT64
| `--*P. cylindrica Claparède & Lachmann 1859 [=*Arplagiophrum cylindricum]LT64
|--Lagynis Schultze 1854 [=Exassula Ehrenberg 1872; incl. Platoum Schulze 1875]LT64
| |--*L. baltica Schultze 1854 [=Difflugia (*Exassula) baltica]LT64
| `--L. parva (Schulze 1875) [=*Platoum parvum]LT64
|--Diplophrys Barker 1868 [Diplophryidae]K14
| |--*D. archeri Barker 1868LT64
| `--D. marinaC-SC06
|--Pilalla Rhumbler 1935K14
| `--*P. exigua Rhumbler 1935 [=Psammosphaera exigua]LT64
`--Psammolagynis Golemansky 2000K14
Lagynidae [Amphistominae, Amphistomini, Armyxothecnia, Belariini, Heterogromiini, Microcometesiidae, Microcometidae, Microgromiidae, Mikrogromiidae, Mikrogromiini, Myxothecinae, Plagiophryiinae, Polystomini]
*Type species of generic name indicated
References
[C-SC06] Cavalier-Smith, T., & E. E.-Y. Chao. 2006. Phylogeny and megasystematics of phagotrophic heterokonts (kingdom Chromista). Journal of Molecular Evolution 62: 388–420.
[G86] Golemansky, V. G. 1986. Rhizopoda: Foraminiferida. In: Botosaneanu, L. (ed.) Stygofauna Mundi: A Faunistic, Distributional, and Ecological Synthesis of the World Fauna inhabiting Subterranean Waters (including the Marine Interstitial) pp. 17–20. E. J. Brill/Dr. W. Backhuys: Leiden.
[K14] Kaminski, M. A. 2014. The year 2010 classification of the agglutinated Foraminifera. Micropaleontology 60 (1): 89–108.
[LT64] Loeblich, A. R., Jr & H. Tappan. 1964. Sarcodina: chiefly “thecamoebians” and Foraminiferida. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt C. Protista 2 vol. 1. The Geological Society of America and The University of Kansas Press.