Papposphaera sagittifera

P. sagittifera cfr. combination coccosphere (Figs 38– 43)

Both the EPOS and ANT X/3 Antarctic Weddell Sea material encompassed combination coccospheres that involve P. sagittifera cfr. HET and a Turrisphaera species that is not identical to P. sagittifera cfr. HOL, nor the Antarctic Turrisphaera sp. described above.

In the heterococcolithophore component the central area calcification is rarely exposed, yet it appears to display (Fig. 41) the same aspects of asymmetry (i.e. a skewed cross bar and randomly oriented peripheral elements) described above for P. sagittifera cfr. HET (Fig. 31). The calyx is a flaring four-winged rosette (Figs 41–42) in which each individual wing shows a pronounced stepwise reduction in width towards the distal tip. The holococcolithophore part is characterized by a pronounced asymmetry in the flagellar pole holococcolith, and a more slender yet overall symmetrical appearance of coccoliths elsewhere in the periplast. The unilateral flaring of the circum-flagellar holococcoliths immediately distinguishes this form from both Antarctic Turrisphaera sp. (Figs 33–37) and Arctic P. sagittifera HOL (Figs 23–26).