Nannotax Enabling nannofossil research

Description: Coccolith structure - the bulk of the coccoliths are formed of superposed layers of crystallites arranged in rhombohedral arrays (in LM these behave optically as a single crystal with oblique c-axis orientation). Outer wall is formed of single crystallite thick layer of crystallites in hexagonal array, with their c-axes radial.

Coccospheres monomorphic, sub-spherical.

Coccolith form - the coccoliths are flat topped discs with a low central spine, they may be either solid or perforate (i.e. with a few pits on their surface).

Remarks: Forms with 7-10 circular depressions were previously distinguished as a separate species, Syracolithus confusus Kleijne 1991. However, coccospheres with both variants occur (Cros et al. 2000, Geisen et al. 2002, Young unpublished obs.) and so it seems clear that the distinction is not genotypic. The variants can be termed H. carteri HOL solid and H. carteri HOL perforate.

Size: Liths 2-3 µm long.

Life-cycle association: The association of these holococcoliths with Helicosphaera carteri has been demonstraed by observation of numerous combination coccospheres, Cros et al. (2000).

Fossil record: Can be common in well-preserved Quaternary sediments (Crudeli et al. 2006).

Synonyms

• Syracolithus catilliferus (Kamptner 1937) Deflandre 1952
• Syracolithus confusus Kleijne 1991