The Polcyclolithaceae are a key group of Cretaceous nannoliths including many biostratigraphic markers. Varol (1992) and Burnett (in Bown 1998) give useful reviews of the group.

Informal taxon-based term: Polycyclolith nannolith formed by the Polycyclolithaceae.
Orientation: clear distal / proximal polarity has not been demonstrated so these terms should be avoided.
Diaphragm plate-like central cycle of elements
Wall outer part of nannolith, typically formed of two superposed cycles of elements.
Reduced cycle smaller of the two wall cycles.
Expanded cyclelarger of the two wall cycles.
Ray, petalloid, block typical shapes of wall elements (cf. section 4.1.2).

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