Taxonomy
Original description: Test relatively large (typically greater than 300 microns in length, average is 304 microns, n = 11), broadly rounded, consists of 9 to 12 chambers (n = 12) that are biserially arranged and globular throughout. The diameter of the proloculus is variable (range = 15 to 32 microns, n = 7) and subsequent chambers rapidly increase in size, resulting in a strongly tapered, subtriangular outline in side and edge views. Sutures are straight, strongly depressed, and generally meet the central axis at a right angle. Aperture is a symmetrical semicircular, low, broad arch at the base of the final chamber, bordered by an imperforate lip. Periapertural flanges are absent. Test wall is calcitic and hyaline. Chamber surface is finely perforate to macroperforate (pore diameter = 0.9 to 3.2 microns, n = 2) and is ornamented with costae that vary from almost completely smooth to those with discontinuous costae that are up to 4.3-microns thick. Distinguishing features. Planoheterohelix praenuttalli is generally large, strongly tapering, and almost as broad (in edge view) as it is wide (in side view).
Entries in the Catalog of original descriptions: Planoheterohelix praenuttalli
Geological Range:
Last occurrence (top): within D. concavata zone (86.71-89.91Ma, top in Coniacian stage). Data source: [copied from Chronos database]
First occurrence (base): within H. helvetica zone (92.56-93.52Ma, base in Turonian stage). Data source: [copied from Chronos 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
Character matrix
test outline: | Triangular | chamber arrangement: | Biserial | edge view: | Equally biconvex | aperture: | Interiomarginal |
sp chamber shape: | Globular | coiling axis: | N/A | periphery: | N/A | aperture border: | Thick flange |
umb chbr shape: | Globular | umbilicus: | N/A | periph margin shape: | Broadly rounded | accessory apertures: | None |
spiral sutures: | Strongly depressed | umb depth: | N/A | wall texture: | Finely costate | shell porosity: | Finely Perforate: 1-2.5µm |
umbilical or test sutures: | Strongly depressed | final-whorl chambers: | 2.0-2.0 | N.B. These characters are used for advanced search. N/A - not applicable |
Haynes, S., Huber, B. T. & MacLeod, K. G. (2015). Evolution and phylogeny of mid-Cretaceous (Albian-Coniacian) biserial planktic foraminifera. Journal of Foraminiferal Research. 44: 42-81. gsReferences:
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Planoheterohelix praenuttallii compiled by the pforams@mikrotax project team viewed: 8-12-2019
Short stable page link: http://mikrotax.org/pforams/index.php?id=110408 Go to Archive.is to create a permanent copy of this page - citation notes |