Nannotax Enabling nannofossil research

Families included: Noelaerhabdaceae, the Palaeogene family Prinsiaceae (see Young & Bown 1997) and the extant family of non-calcifying haptophytes Isochrysidaceae (Edvardsen et al. 2000).The order Isochrysidales is used instead of Prinsiales Young & Bown 1997, since it has priority.
Grouping of the Isochrysidaceae and Noelaerhabdaceae is based on flagellar characters (haptonema vestigial) and is supported by biochemical characters (production of alkenones) and molecular genetics (Edvardsen et al. 2000, Fujiwara et al. 2001, Sáez et al. 204). Grouping of Prinsiaceae and Noelaerhabdaceae is based on coccolith structure and stratophenetic data (Young et al. 1992, Young & Bown 1997).

Genera:

Tyical specimens	Outline description	Range
	Emiliania - slits between each element of the distal shield	NN21
	Gephyrocapsa - bridge across central area	NN15-21
	Pseudoemilainia - slits beween some elements of distal shield	NN15-19
	Reticulofenestra - without slits or bridge	Eocene-NN21
	Cyclicargolithus - circular and with small central area	Eocene-NN7
	Noelaerhabdus - with spine grown from inner tube elements	NN10-11 (Paratethyan endemic)
	Bekelithella - with circlet of spines around cenral area	NN10-11 (Paratethyan endemic)

Description: Coccoliths are placoliths but unlike the Coccolithaceae, growth does not occur downward from the proto-coccolith ring. The R-unit is always well developed, forming a proximal shield element, two tube elements with opposite senses of imbrication, and usually a central-area element. The locus of the proto-coccolith ring is usually marked by a ring of slits on the proximal surface. Central-area structures are always conjunct, being formed from either the central-area element or the inner tube element of the proximal shield
In the Prinsiaceae the V-unit is well developed (Toweius-type structure); forming an upper layer to the proximal shield, an outermost tube and the distal shield.
In the Noelaerhabdaceae the V-unit is virtually absent (Reticulofenestra-type structure) and the outer of the two R-unit tube cycles is extended to form the distal shield.