Müller, 1858, emend. Strelkov and Reshetnjak, 1971
Colonial polycystines, each individual has a single, thin-walled, spherical or subspherical latticed shell. The Collosphaeridae is the only group of colonial polycystines with complete latticed shells. Colonies consist of a gelatinous mass (which obviously disappears in the sedimentary record, as well as in many net-plankton samples where it breaks down) in which hundreds to thousands of shells are immersed (C. Polycystina (Spumellaria); C. Polycystina (Spumellaria) 2).
The shape of the colony is not species-specific; it may be spherical, ellipsoidal, cylindrical, ribbon-shaped, etc., measuring up to several centimeters in length and a few millimeters in diameter. The siliceous shells are always represented by a single perforated sphere (internal spheres are never present), with or without centrifugal (external) or centripetal (internal) tubular projections and/or spines. Spines (when present) are conical (circular in cross-section).
As with most other polycystines, specific assignments are based almost exclusively on the skeleton; however, studies of entire colonies, which allow investigating the intraspecific morphologic variability of the collosphaerids, indicate that quite dissimilar shell morphotypes can coexist within the same colony, thus stressing the assumption that at least some of the specific divisions based on the siliceous sphere alone are spurious (e.g., Kleijne, 1987; Petrushevskaya and Swanberg, 1990).
The following species of this family are treated in the present volume (arranged in three groups according to external surface morphology):
[1] External surface without spines or tubes [e.g. Collosphaera macropora 2]
Buccinosphaera invaginata
Collosphaera huxleyi
Collosphaera macropora
Collosphaera tuberosa
Tribonosphaera centripetalis
[2] External surface spiny or thorny [e.g. Acrosphaera murrayana 2]
Acrosphaera murrayana
Acrosphaera spinosa
[3] External surface with 3-4 to many tubes
[e.g. Siphonosphaera polysiphonia 2; Solenosphaera chierchiae 2]
Siphonosphaera martensi
Siphonosphaera polysiphonia
Solenosphaera chierchiae
Solenosphaera polysolenia
Solenosphaera zanguebarica