Nannotax

Coccolith structure: Coccoliths are placoliths with Reticulofenestra-type structure, i.e. V-unit vestigial, R-unit forms proximal shield, distal shield, inner andouter tube-cycles, grill and any central-area structures; strongly birefringent. In the SEM characteristic features include; grill in central area, anti-clockwise imbrication of inner tube elements, and monocyclic proximal shield. References: Young (1989), Young et al. (1994).

Genera included:

Typical specimen	Genus	Range	Distinguishing features
	Reticulofenestra	Eocene-Recent	Elliptical, central area open or closed
	Cyclicargolithus	Eocene-NN	Circular with narrow central area
	Pseudoemiliania	NN14-19	Numerous slits in distal shield
	Gephyrocapsa	NN14-21	Bridge over central area
	Emiliania	NN21	Slits between all distal shiled elements
	Noelaerhabdus	NN10-11	Paratethyan endemic wth large spine
	Bekelithella	NN10-11	Paratethyan endemic wth circlet of spines

Life-cycles and culture studies: Emiliania huxleyi and Gephyrocapsa oceanica have been cultured extensively and their life-cycle is well worked out (Klaveness 1972, Green et al 1996, Houdan et al. 2003). The dominant phase is diploid, non-motile and usually heterococcolith-bearing (= C-cells), although naked mutants often occur inculture (= N-cells). The alternate phase is haploid, scale-bearing and motile(= S-cells). There is no holococcolith stage.

Fossil Record: The Noelaerhabdaceae dominate most Neogene nannofossil assemblages with the dominant genera being succesively Cyclicargolithus (NN1-6), Reticulofenestra (NN6-16), Pseudoemiliania (NN16-19), Gephyrocapsa (NN19-20) and Emiliania (NN21). The last occurrences of various larger forms provide excellent highly synchronous biostatigraphic events - particularly LO large R. pseudoumbilicus (end NN10A), LO R. pseudoumbilicus (end NN15), LO large Gephyrocapsa (NN19), LO P. pseudoemiliania (end NN19).

Synonym: Gephyrocapsaceae Black, 1971