|Daughter taxa: (blue => in age window 0-800Ma)|
|H. orientalis and variant|
Small species. Flange ends abruptly, no wing or spur. Central-area with inversely oriented pores.
Like H. orientalis but central-area granular, without well defined pores.
|H. obliqua and variants|
Large sized, ovoid shape. Only weakly birefringent. Wing ends in spur, central-area with two prominent pores with inverse orientation.
Like H. obliqua but more rectangular
Like H. obliqua but more elongate
Like H. obliqua but more elongate and rectangular
Like H. obliqua but shorter
|H. recta and variants|
Large size, sub-rectangular shape. Wing ends in spur, central-area with two large pores separated by narrow conjunct bar.
Like H. recta but pores very small
Like H. recta but pores larger
Simlar to H. obliqua but flange continuous, without notch
Very large, rounded species, with closed central-area, or two narrow slits.
Distinguishing features: Late Oligocene to Mid Miocene species; flange terminates abruptly rather than expanding into a wing; blanket largely confined to central area, so flange is dark is dark in cross-polars; bar conjunct with rim, horizontal or inversely oriented.
Farinacci & Howe catalog pages:
Morphology: Distinctive group of Late Oligocene to Mid Miocene Helicosphaera species, with flange terminating abruptly rather than expanding into a wing. Blanket largely confined to central area, so flange is dark is dark in cross-polars. Central area openings usually show inverse orientation (i.e. they point toward the flange termination). Bar conjunct with rim.
|Metrics||Lith size: 4->12µm;|
Last occurrence (top): near top of Messinian Stage (86% up, 5.6Ma, in Messinian stage). Data source: Total of range of species in this database
First occurrence (base): in lower part of Priabonian Stage (20% up, 37Ma, in Priabonian stage). Data source: Total of range of species in this database
Plot of occurrence data:
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