Trigonaspis Thomsen 1980a

Thomsen, Helge A. & Østergaard, Jette B., 2015, Coccolithophorids in Polar Waters: Trigonaspis spp. Revisited, Acta Protozoologica 54 (2), pp. 85-96 : 86-87

Trigonaspis Thomsen 1980a

The original description of this holococcolithophorid genus as reproduced below was based on material from West Greenland:

Small biflagellate coccolithophorids with a short haptonema. Periplast composed of coccoliths which are tower-like near the flagellar pole. Coccolith crystallites small triangular plates composed of three subunits. Small organic scales, always unmineralized, appear below the coccolith base-plates.

Type species: Trigonaspis diskoensis

The key characteristics are dimorphic (occasionally varimorphic) coccoliths that involves a tuft of tower-shaped coccoliths encircling the flagellar pole, and above all the monolayer of triangular crystallite groups that cover all coccolith surfaces.

The most closely related genus is Turrisphaera Manton et al. 1976b which is distinguished from Trigonaspis based on the presence of hexangular rather than triangular crystallite groups. Circumstantial evidence in support of this distinction has subsequently come from the discovery of combination cells ( Thomsen et al. 1991) where Papposphaera spp. share a common life history with Turrisphaera spp. , while species of Trigonaspis interact with species of Pappomonas (see also Thomsen and Østergaard 2014b).

Three species of Trigonaspis , viz. T. diskoensis Thomsen, 1980a , T. minutissima Thomsen, 1980a and T. melvillea Thomsen in Thomsen et al. (1988) have been described so far. A fourth species ( Pappomonas garrisonii HOL = Trigonaspis sp. ) is illustrated and discussed here based on material from the Antarctic.