Protoheterohelix

Daughter taxa (time control age-window is: 0-800Ma)
			Protoheterohelix obscura
			Protoheterohelix washitensis
			Protoheterohelix sp. Specimens which cannot be assigned to established species

Taxonomy

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:
Parent taxon (Heterohelicidae): Aperture symmetrical, ranging from a low slit to a high arch at the base of the final chamber, becoming terminal in uniserial taxa.
This taxon: Biserial throughout, aperture asymmetrically positioned, wall texture smooth.

Geological Range:
Last occurrence (top): at top of H. helvetica zone (100% up, 92.5Ma, in Turonian stage). Data source: Total of ranges of the species in this database
First occurrence (base): within P. ticinensis zone (101.92-103.94Ma, base in Albian stage). Data source: Total of ranges of species in this database

Plot of range and occurrence data:

• Range-bar - range as quoted above, pink interval top occurs in, green interval base occurs in.
• Triangles indicate an event for which a precise placement has been suggested
• Neptune data: This is a higher taxon page so Neptune data is not plotted. See also: customisable plot Parent: Heterohelicidae

Protoheterohelix compiled by the pforams@mikrotax project team viewed: 7-10-2024 Taxon Search: Advanced Search Short stable page link: https://mikrotax.org/pforams/index.php?id=110445 Go to Archive.is to create a permanent copy of this page - citation notes

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