Nannotax Enabling nannofossil research

Description: Circular heterococcoliths with a single shield and open central area, surronuded by a collar/tube. Formed of a single cycle of crystal-units with sub-vertical c-axes (Young et al. 1998).

	modern
	fossil

 Remarks (relation to ceratoliths): A succesion of observations (Alcober & Jordan 1997, Young et al. 1998, Cros et al. 2000, and Sprengel & Young 2000) have shown that these heterococcoliths are formed during an alternate life-cycle stage of Ceratolithus cristatus and so should not be regarded as a discrete species.

Synonyms:

• Neosphaera Lecal-Schlauder 1950
• Craspedolithus Kamptner 1963 

Variants: three different forms can be identified in the modern plankton (Kleijne 1993), and may represent discrete species, although given the life-cycle complexities it is simpler to place them all in C. cristatus.

1. large coccolithomorpha type: 6-10 µm across, opening 0.4-0.5x total diameter [= Neosphaera coccolithomorpha Lecal-Schlauder 1950].
2. small coccolithomorpha type: 4-5 µm across, opening 0.35-0.45x total diameter.
3. nishidae type: 4-7 µm across, opening 0.15-0.3x total diameter [=Neosphaera coccolithomorpha var. nishidae Kleijne 1993].

Range: Quite common in the Quaternary and has been observed back to at least the mid Pliocene, but is not routinely recorded since it is difficult to sperate from Umbilicosphaera in the LM. NB The first occurrence does sem to approximately conicide with that of Ceratolithus ceratoliths, but there is no obvious reason why this should be the case since the ancestor of Ceratolithus (Triquetrorhabdulus?) might be precidited to have formed heterococcoliths.