Distinguishing features: Large, circular Pemma with a diagnostic thin base with crenulated edges. Central area consists of a layer of basal thickenings superimposed on the base, resulting in a hazy appearance of the outer edge of the nannolith and a central area more highly birefringent than the edges.
Farinacci & Howe catalog pages: Pemma bybelliae *
Morphology remarks: Similar in shape to P. rotundum, which lacks the thin base exhibited by P. bybelliae. Pemma balium is the only other described member of this genus to exhibit a thin base, and it is easily distinguished from P. bybelliae by its subcircular outline (Self-Trail 2011).
Size: Diamter 7.5-13.5µm
|Tags||LITHS: nannolith-radiate, pentagonal, CA: pores, |
CSPH: not known, T-UNITS: all, T-prominent,
|Metrics||Lith size: 7->14µm; Segments: 5->5; |
Sources: lith size (diameter) from OD
Last occurrence (top): within NP16 zone (40.40-42.87Ma, top in Bartonian stage). Data source: Self-Trail 2011
First occurrence (base): within NP16 zone (40.40-42.87Ma, base in Lutetian stage). Data source: Self-Trail 2011
Plot of occurrence data:
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