Orastrum colligatum


Classification: Mesozoic -> Holococcoliths -> Common genera -> Orastrum -> Orastrum colligatum
Sister taxa: O. asarotum, O. campanensis, O. porosuturalis, O. perspicuum, O. robinsonii, O. colligatum, O. sp.,

Distinguishing features: Holococcolith formed of four large interlocking blocks forming both a rim and central cross.


Taxonomy:

Citation: Orastrum colligatum Henderiks & Ziveri, 1997
Rank: Species
Notes & discussion: The taxonomic concept of Orastrum has evolved since the description of this species and it's placement here is now clearly anomalous, since it lacks the dark rim characteristic of Orastrum. It would be better placed in Calculites 

Farinacci & Howe catalog pages: Orastrum colligatum *

Distinguishing features: Holococcolith formed of four large interlocking blocks forming both a rim and central cross.


Morphology remarks: "Medium-sized, elliptical, moderately-birefringent holococcolith constructed of four smooth. interlocking. crystallographically-coherent blocks, forming an offset X in the central area." [Henderiks & Ziveri 1997]

Geological Range:
Last occurrence (top): within Cenomanian Stage (93.90-100.50Ma, top in Cenomanian stage). Data source: Burnett 1998
First occurrence (base): within Albian Stage (100.50-112.95Ma, base in Albian stage). Data source: Burnett 1998

Plot of occurrence data:

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

    References:

    Burnett, J. A. (1998). Upper Cretaceous. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series. 132-199. gs

    Henderiks, J. & Ziveri, P. (1997). Orastrum colligatum, a new holococcolith species from the Upper Albian-Cenomanian of the Russian Craton (Ukraine). Journal of Nannoplankton Research. 19(2): 109-111. gs


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    Orastrum colligatum compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 12-11-2019

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