pforams@mikrotax - Planoheterohelix olssoni pforams@mikrotax - Planoheterohelix olssoni

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. labellosa, P. sphenoides, P. stenopos, P. vistulaensis, 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

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

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 range and occurrence data:


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: 25-3-2023

Taxon Search:
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AphiaID: 1034792 Nomenclatural data on WoRMS
Short stables page link: Go to to create a permanent copy of this page - citation notes

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