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.

Narrow rim with thin, imperforate plate across wide central-area.

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: informal group

Farinacci & Howe catalog pages:

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: 18-10-2019

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