Rarer genera


Classification: Mesozoic -> Holococcoliths -> Rarer genera
Sister taxa: Common genera, Rarer genera,

Short diagnosis: Less common genera


Daughter taxa (blue => in age window 0-300Ma) Granddaughter taxa
Disk-shaped holococcoliths
Holococcoliths formed from two blocks divided by a transverse suture.

Holococcolith with narrow rim and two blocks in central area

Holococcoliths formed from ~7 triangular blocks with irregular blocks in the central-area.

Holococcoliths formed from 4-12 blocks with central-area filled or spanned by disjunct bar or block.

Holococcolith formed of 8 blocks, typically 4 large and 4 small.

Elliptical holococcolith with broad rim of numerous small blocks and central area of two or more blocks

Elliptical holococcolith with rim of multiple small elements, central are on except for bridge across short axis.

Elliptical coccolith formed of a single block, with two perforations

Holococcoliths with rim of 12-14 blocks and central-area spanned by a narrow, dark bar.

Holococcoliths with rim of 10-26 blocks and central perforation.

Holococcoliths with rim formed from 8-12 elements, and 2 longitudinally-oriented elongate blocks in the central-area.

Other forms - mostly cavate
Holococcoliths with a proximal plate of three blocks and tall, tapering spines.

Elliptical, cavate (and usually septate) holococcoliths, often bearing hollow spines. Distal surfaces may be perforate and there may be internal buttresses.

Cavate holococcolith with central septum



Cavate, conical-flask shaped holococcolith with lid and internal partition.

Conical shaped holococcolith, usually seen in side view, base weak or absent

Cavate holococcoliths with thin rims and small spines; whole holococcolith behaves as a single crystal in xpl,

Domed-shaped holococcoliths with holes or cavities.

Solid, truncated-cone-shaped nannolith with rectangular cross-section constructed from minute, roughly equidimensional crystallites. Possibly a holococcolith.

Holococcoliths usually seen in side view and comprising a thick proximal plate and spine or process, typically with a cavity or axial canal.

Holoccolith with elliptical base and five-rayed process

Cavate holococcolith with internal walls and distal protrusions

Cavate holococcolith with box-shape, high rim and thin proximal plate, short spine on distal surface



Taxonomy:

Rank: informal group

Farinacci & Howe catalog pages: Rarer genera [no catalog entry yet]

Short diagnosis: Less common genera

Geological Range:
Last occurrence (top): within Thanetian Stage (55.96-59.24Ma, top in Thanetian stage). Data source: Total of range of species in this database
First occurrence (base): within Toarcian Stage (174.15-182.70Ma, base in Toarcian stage). Data source: Total of range of species in this database

Plot of occurrence data:


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Rarer genera compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 16-12-2017

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