Further observations on the genusPappomonasManton et Oates with special reference toP. virgulosasp. nov. from West Greenland

Abstract

Electron microscopy of dried preparations of Arctic nanoplankton has permitted a second species of the recently erected genus Pappomonas Manton et Oates to be described and named. P. virgulosa sp. nov. is characterised by coccolith appendages composed of a central shaft ending in a cluster of four finger-like rods. There are also calcified plates of characteristic construction, without appendages. Detailed observations on the coccoliths, especially on the shapes and arrangement of component calcite crystallites and the presence of unmineralised components, have permitted further comparisons to be made with equivalent structures in Papposphaera lepida Tangen, recently investigated in the southern hemisphere, as well as with Pappomonas flabellifera Manton et Oates. As a working hypothesis, an interpretation of coccolith morphology in all three taxa has been formulated in terms of known structural components of uncalcified scales in Chrysochromulina spp. The need for fuller information on certain details, notably the coccolith bases in Pappomonas spp. is stressed.