Family NOELAERHABDACEAE Jerkovic 1970 emend. Young & Bown 1997
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).
|Reticulofenestra||Eocene-Recent||Elliptical, central area open or closed
|Cyclicargolithus||Eocene-NN8||Circular with narrow central area
||Numerous slits in distal shield
||Bridge over central area
||Slits between all distal shield elements|
||Paratethyan endemic with large spine
||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.