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Schackoina bicornis


Classification: pf_mesozoic -> Schackoinidae -> Schackoina -> Schackoina bicornis
Sister taxa: S. bicornis, S. cenomana, S. multispinata, S. sp.,

Taxonomy

Citation: Schackoina bicornis Reichel, 1948
Rank: Species
Basionym: Schackoina cenomana bicornis

Type images:

Original description: Translated from French: The coiling appears to be more or less planispiral, sinistral, as far as one can judge from the specimens soaked in essential clove oil. Inflated chambers, first with a spherical shape then pear-shaped, numbering 7 to 8 (without taking the proloculus into account) and arranged in about two whorls. The first chambers, always mostly covered by those of the second whorl, are not always clearly seen in our specimens. At the end of the first whorl, they already bear a little spine. The last 4 chambers are set in a cross-like manner. The last chamber is inflated like a goat-skin bottle and shows two papillae which are the long spine points of attachment, as shown in the thin sections. Very often, the spines have a narrow base and taper very slowly, implying that they were very long. None of our sections display their full length. The latter must have been notably longer than the diameter of the chambers that support them (see fig. 8). From the 4th chamber up to the penultimate chamber there is only one spine per chamber, equatorially oriented (not always exactly so, frequently deflected). The last chamber bears two spines oriented more or less exactly in a plane perpendicular to the equatorial (coiling) plane, but obliquely directed. The angle at which the two spines of the last chamber meet varies in value. It is generally higher than 90° and may reach 140° (fig. 9). Aperture not visible in our examined specimens.

L'enroulement paraît à peu près planispiral et sinistrogyre, autant qu'on peut en juger d'après les exemplaires immergés dans de l'essence de girofle. Loges renflées, d'abord sphériques, puis piriformes, au nombre de 7 à 8 (sans compter le proloculum) disposées sur 2 tours environ.
Les premières loges, toujours en grande partie recouvertes par celles du 2ème tour, ne sont pas très nettement visibles sur nos exemplaires. A la fin du premier tour, elles portent déjà une petite épine. Les 4 dernières loges sont disposées en croix. La dernière est renflée en forme d'outre et présente deux protubérances qui sont les points d'insertion de longues épines comme le montrent les coupes minces.
Les épines sont le plus souvent étroites à leur base et ne s'amincissent que très graduellement, ce qui semble indiquer qu'elles devaient être très longues. Aucune de nos coupes ne les montrent entières. Leur longueur devait en tout cas dépasser notablement le diamètre radiane des loges qui les portent (voir fig. 8).
Jusqu'à l'avant-dernière loge et à partir de la lème, il n'y a qu'une épine par loge, orientée dans le plan equatorial (pas toujours exactement, les déviations sont fréquentes). La dernière loge porte deux épines orientées plus ou moins exactement dans un plan perpendiculaire au plan equatorial ou plan d'enroule¬ ment, mais dirigées obliquement. L'angle que forment entre elles les deux épines de la dernière loge est variable. Il est en général supérieur à 90° et peut atteindre 140° (fig. 9).
L'ouverture n'est pas visible sur nos exemplaires.

Entries in the Catalog of original descriptions: Schackoina cenomana bicornis

Geological Range:
Last occurrence (top): within R. cushmani zone (94.03-95.94Ma, top in Cenomanian stage). Data source: [copied from Chronos database]
First occurrence (base): within T. globotruncanoides zone (96.08-100.50Ma, 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

  • Histogram - Neptune occurrence data from DSDP and ODP proceedings. Pale shading <50 samples in time bin. Interpret with caution & read these notes
  • Note to users in China - the diagram may not plot unless you use a VPN since I use google services on the website. If this is a problem please contact me 谢谢.
  • Taxon plotted: Schackoina bicornis, synonyms included - Schackoina bicornis; Schackoina cenomana bicornis;
  • space-time plot :: Samples map :: Parent: Schackoina

    Character matrix

    test outline:Stellatechamber arrangement:Pseudoplanispiraledge view:Hourglassaperture:Equatorial
    sp chamber shape:Elongatecoiling axis:Moderate-highperiphery:N/Aaperture border:Thin lip
    umb chbr shape:Elongateumbilicus:Wideperiph margin shape:Subangularaccessory apertures:Relict
    spiral sutures:Moderately depressedumb depth:Shallowwall texture:Smoothshell porosity:Finely Perforate: 1-2.5µm
    umbilical or test sutures:Moderately depressedfinal-whorl chambers:4.0-4.5 N.B. These characters are used for advanced search. N/A - not applicable

    References:

    Leckie, M. (1984). Mid-Cretaceous planktonic foraminiferal biostratigraphy off Central Morocco, Deep Sea Drilling Project Leg 79, Sites 545 and 547. Initial Reports of the Deep Sea Drilling Project. 79: 579-620. gs :: ::

    Reichel, M. (1948). Les Hantkéninidés de la Scaglia et des Couches rouges (Crétacé supérieur). Eclogae Geologicae Helvetiae. 40 [1947](2 [1947]): 391-409. gs :: ::


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    Schackoina bicornis compiled by the pforams@mikrotax project team viewed: 5-8-2020

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    Short stable page link: http://mikrotax.org/pforams/index.php?id=110520 Go to Archive.is to create a permanent copy of this page - citation notes



    Comments (1)

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    Le Coze

    no brackets no..

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    Jeremy Young (UK)

    thanks, corrected

    Page 1 of 1
     

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