Planoheterohelix olssoni

Classification: pf_mesozoic -> Heterohelicidae -> Planoheterohelix -> Planoheterohelix olssoni
Sister taxa: P. globulosa, P. moremani, P. olssoni, P. papula, P. paraglobulosa, P. planata, P. postmoremani, P. praenuttallii, P. reussi, P. rumseyensis, P. sp.,


Citation: Planoheterohelix olssoni (Georgescu, 2000)
Rank: Species
Basionym: Heterohelix olssoni
Taxonomic discussion: Heterohelix olssoni n.sp. differs from H. moremani (Cushman) in having (1) larger planispirally enrolled stage, (2) reduced number of paired chambers in the biserial part of the test, (3) greater values of the W/Lmax ans Lps/Lmax ratios (4) absence of striae on the chamber surface and (5) generally smaller size. While Heterohelix moremani (Cushman) is a typical representative of the genus while, H. olssoni n.sp. appears to be a descendant of the primitive heterohelicids, as it exhibits large planispirally enrolled earlier test stage. [copied from Chronos database]

Type images:

Original description: Stout test having well developed early planispirally enrolled test. The primary stage is followed by a biserial one consisting of two to (rarely) tree pairs of chambers. Chambers subglobular to globular, sometimes slightly dorso-ventrally flattened. Sutures straight to slightly depressed. Wall finely perforate. Test surface is smooth, unornamented, lacking any trace of striae. Primary aperture, a low arch at the base of the last formed chamber, is bordered by a narrow imperforate lip.

Entries in the Catalog of original descriptions: Heterohelix olssoni

Geological Range:
Last occurrence (top): within T. reicheli zone (95.94-96.08Ma, top in Cenomanian stage). Data source: [copied from Chronos database]
First occurrence (base): within T. reicheli zone (95.94-96.08Ma, base in Cenomanian 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

  • (NB There is no histogram as there are no occurrence records for the taxon in the Neptune database) Parent: Planoheterohelix

    Character matrix

    test outline:Subtriangularchamber arrangement:Biserialedge view:Compressedaperture:Interiomarginal
    sp chamber shape:Globularcoiling axis:N/Aperiphery:N/Aaperture border:Thin lip
    umb chbr shape:Globularumbilicus:N/Aperiph margin shape:Broadly roundedaccessory apertures:N/A
    spiral sutures:Flushumb depth:N/Awall texture:Smoothshell porosity:
    umbilical or test sutures:Flushfinal-whorl chambers:2.0-2.0 N.B. These characters are used for advanced search. N/A - not applicable


    Georgescu, M. D. (2000). Late Albian-Turonian planktonic foraminifera in the Romanian western Black Sea offshore. Revista Española de Micropaleontología. 32: 157-173. gs


    Planoheterohelix olssoni compiled by the pforams@mikrotax project team viewed: 17-2-2020

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    Short stable page link: http://mikrotax.org/pforams/index.php?id=110403 Go to Archive.is to create a permanent copy of this page - citation notes

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