Nannotax Enabling nannofossil research

Family characterised by ornate horseshoe-shaped nannoliths formed from a single calcite crystal unit, termed ceratoliths. Includes the extant genus Ceratolithus and extinct genus Amaurolithus, which have similar shape but different crystallographic orientations. Raffi et al. (1999) documented likely evolutionary relationships between Ceratolithus and the fossil genera Amaurolithus and Triquetrorhabdulus.

Taxa included:

A. amplificus	A. delicatus	A. primus	A. tricorniculatus	C. armatus	C. atlanticus	C. cristatus
Amaurolithus - dark in xpl				Ceratolithus - bright in xpl

Life cycle: Classic observations of Norris (1971) showed that typically a single ceratolith was wrapped around the cell and that beyond the ceratolith a large coccosphere of hoop-shaped coccoliths sometimes occurs. These large coccospheres can contain up to four cells each with ceratoliths.

More recently, Alcober & Jordan (1997) observed C. cristatus hoop-shaped coccoliths inside coccospheres of "Neosphaera coccolithomorpha" planoliths, suggesting that ceratoliths, planoliths and hoop coccoliths may form during alternate phases of a complex life-cycle. These observations have been strongly confirmed by Young et al. (1998), Cros et al. (2000) and Sprengel & Young (2000). The “Neosphaera” planoliths show typical heterococcolith features, hence a likely hypothesis is that the ceratolith stage is equivalent to the holococcolith stage in other taxa, and so haploid (see also discussion in Young et al. 2005). Molecular genetic data and culture observations not yet available.