|Daughter taxa (blue => in age window 0-300Ma)|
Original description: Protoheterohelix:
Entries in the Catalog of original descriptions: Protoheterohelix;
Short diagnosis: Test is biserial throughout, with variable asymmetry as seen in edge view. Earlier species display twisted tests and symmetrical periapertural structures; evolved ones show symmetrical tests in edge view and asymmetrical periapertural structures. When compared with the second chamber, the size of the proloculus is variable and generally larger, but in some rarer specimens it is smaller. Chamber shape is globular to reniform. Sutures are distinct, depressed, straight, and oblique to the test axis of growth. Test periphery is rounded. Aperture is low to medium high arch at the base of the last formed chamber and bordered by asymmetrical periapertural structures. Periapertural structures of the primitive species consist of a
subangular ridge on one side and a rim on the opposite side; two asymmetrical flanges border the aperture in the evolved
species. A small relict toothplate can be occasionally present. Chamber surface is smooth. Test wall is calcitic, hyaline, nannoperforate to microperforate.
Last occurrence (top): within Turonian Stage (89.77-93.90Ma, top in Turonian stage). Data source: Total of range of species in this database
First occurrence (base): within Albian Stage (100.50-112.95Ma, base in Albian stage). Data source: Total of range of species in this database
Plot of occurrence data:
NB Plotting of Neptune data has been disabled on the Mesozoic pages because the dataset is both small and badly affected by a few sites with erroneous age models (our obs Huber, Petrizzo, Young, Nov 2016). The data can still be viewed via the range plottertool - tools menu.
Protoheterohelix compiled by the pforams@mikrotax project team viewed: 13-12-2017
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