|Daughter taxa (time control age-window is: 0-800Ma)|
Pemma with crenulate edges.
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.
Pemma with multiple nodes along the outer margin of each pentalith.
Circular Pemma species
Angular Pemma species with ray tips extending beyond the pentagonal periphery
Relatively large (typically >5 µm), triangular-shaped nannoliths that thicken along the longer sides and exhibit low birefringence in XPL.
Large (typically >7 µm), triangular-, rectangular- or rhomb-shaped nannoliths, which are thickened along two sides (‘base’ and ‘side’) to give a hook-shaped appearance. Dark in XPL but birefringent where thickened; c-axis orientation is parallel with the long axis.
Specimens which cannot be assigned to any established species
Distinguishing features: Pentaliths with a central depression/perforation in each segment; often producing elevated, robust structures that are commonly observed in side view.
Farinacci & Howe catalog pages: Pemma *Search data:
|Tags||LITHS: nannolith-radiate, pentagonal, CA: pores, CROSS-POLARS: T-prominent,|
|Metrics||Lith size: 5->18µm; Segments: 5->5;|
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): at base of Lutetian Stage (0% up, 47.8Ma, in Lutetian stage). Data source: Total of range of species in this database
Plot of occurrence data:
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