|Daughter taxa: (blue => in age window 0-800Ma)|
Original description: Test is biserial throughout, with variable asymmetry as seen in edge view. Earlier species displays twisted tests and periapertural structures; evolved one shows 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 a 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.
Entries in the Catalog of original descriptions: Protoheterohelix
Distinguishing features: Biserial throughout, aperture asymmetrically positioned, wall texture smooth.
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:
Dec 2017 - Plotting of Neptune data has been re-enabled on the Mesozoic pages following revision of the age-models in Neptune. The data is, however, still very sparse for the Early Cretaceous
Protoheterohelix compiled by the pforams@mikrotax project team viewed: 29-9-2020
Short stable page link: http://mikrotax.org/pforams/index.php?id=110445 Go to Archive.is to create a permanent copy of this page - citation notes