placoliths inc sedis

Classification: Mesozoic -> Heterococcoliths inc sedis -> placoliths inc sedis
Sister taxa: Papposphaeraceae, Unidentified Mesozoic heterococcoliths, globular inc sedis, muroliths inc sedis, placoliths inc sedis, planoliths inc sedis,

Daughter taxa: (blue => in age window 0-800Ma) Granddaughter taxa

Elongate, rounded-oblong placoliths with unicyclic distal shields built of numerous (>50) narrow elements

Unicyclic, elliptical and circular placolith coccoliths with a narrow or closed central area and a characteristically dark gray (low birefringence) XPL image.

Circular placoliths with moderately birefringent shields, a bright inner tube cycle and narrow or closed central areas.

Cretarhabdids with a distinctly dark image in XPL. The type species has broadly elliptical shields and a narrow central area filled with a broad plate/axial cross; the plate is also dark under XPL but is crossed by at least four extinction lines.

Placoliths with monocyclic distal shield with numerous, narrow elements and central-area spanned by ~20 radial bars. In LM the coccoliths are distinctive but inconspicuous with low birefringence, "flaring" image.


Citation: placoliths inc sedis
Rank: Family

Farinacci & Howe catalog pages:

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

Geological Range:
Last occurrence (top): in lower part of Rupelian Stage (17% up, 32.9Ma, in Rupelian stage). Data source: Total of range of species in this database
First occurrence (base): in upper part of Tithonian Stage (62% up, 147.7Ma, in Tithonian stage). Data source: Total of range of species in this database

Plot of occurrence data:



placoliths inc sedis compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 12-8-2020

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