Nannotax Enabling nannofossil research

Coccolith structure: Coccoliths are placoliths with Reticulofenestra-type structure, i.e. V-unit vestigial, R-unit forms proximal shield, distal shield, inner and outer 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-NN8	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 shield elements
	Noelaerhabdus	NN10-11	Paratethyan endemic with large spine
	Bekelithella	NN10-11	Paratethyan endemic with 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

Informal term: The phrase "Noelaerhabdaceaen coccoliths" is ugly and many workers have used alternatives. I reccomend using "reticulofenestrid coccolith" since these all have the same basic structure as Reticulofenestra. Phrases such as "small placoliths" are misleading since unrelated coccolithophores such as Umbilicosphaera produce equally small placoliths.