Mesozoic Nannoplankton

Classification: Mesozoic
Sister taxa:

Distinguishing features: Mesozoic nannofossils - Cenozoic and extant taxa are in a separate module

Daughter taxa: (blue => in age window 0-800Ma) Granddaughter taxa
Tiered placoliths with 3-5 closely-appressed shields.

Murolith coccoliths with V-units forming a narrow imbricate outer wall and R-units extending to form a wide inner rim cycle or plate. Most with a spine bearing central cross.

Murolith coccoliths with a distal/outer cycle of non-imbricating elements, i.e., in side view, the sutures are vertical or near-vertical.

Placolith (or modified placolith) coccoliths showing little or no imbrication. Typically, V-units form distal shield, R-units form proximal shield.

Placolith (or modified placolith) coccoliths with a distal cycle of clockwise-imbricating elements. R-units well developed, forming proximal and distal shield elements with opposite senses of imbrication; V-units typically form a narrow distal cycle near the inner edge of the shield.

Heterocococcoliths with central area including a cycle of radial laths alternating with rim elements but with tangential c-axis orientations

Heterococcolith genera which do not show characteristic features of any of the well-established families.

Holococcoliths & Nannoliths
Coccoliths formed of minute (ca 0.1µm) rhombohedral micro-crystals. Often a life-cycle stage with heterococcolith counterpart(s).

Nannoliths formed of multiple layers of thin elements, arranged with rotational symmetry, and showing tangential c-axis orientations.

Nannofossils not obviously homologous with heterococcoliths, holococcoliths, or braarudosphaeralids

Calcispheres and other non-coccoliths found in nannofossil preps. Some taxa previously placed here have been moved to the calcareous dinoflagellates pages [Feb 2017]. 


Notes & discussion: The Cretaceous/Paleogene extinctions had a massive effect on calcareous nannofossils with virtually all common species becoming extinct, hence it is convenient to treat Mesozoic and Cenozoic nannoplankton separately. They are not, however, phylogenetically separate groups since there are significant common features between them (e.g. V and R mode calcification in heterococcoliths, Young et al. 1991), and since it is commonly accepted that the Cenozoic orders each originated, separately, from Mesozoic precursors (e.g. Perch-Nielsen 1979, Medlin et al. 2008, Bown et al. 2017).
The most important overviews of Mesozoic nannofossils are given by Perch-Nielsen (1985) and in the various chapters in Bown (1998). In addition Bown & Young (1997) introduce the taxonomy used in Bown (1998), and we largely follow that taxonomy here.

Farinacci & Howe catalog pages:

Distinguishing features: Mesozoic nannofossils - Cenozoic and extant taxa are in a separate module

Search data:
MetricsLith size: 0->0µm;
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Last occurrence (top): Extant Data source: Total of range of species in this database
First occurrence (base): at top of No known fossil record modern (100% up, 0Ma, in stage). Data source: Total of range of species in this database

Plot of occurrence data: