Orastrum


Classification: Mesozoic -> Holococcoliths -> Common genera -> Orastrum
Sister taxa: Calculites, Lucianorhabdus, Orastrum, Owenia,

Distinguishing features: Holococcoliths with narrow rim surrounding a central-area formed of 1-4 blocks. Typically non-cavate with no spine. Rim bright and central plate dark


Daughter taxa: (blue => in age window 0-800Ma)
4 central blocks
Central plate of 4, high birefringence blocks - obliquely oriented; central pore. Medium sized (ca. 4-6 µm)
Central plate of 4, low birefringence, blocks - one per quadrant. Large (ca 8-11 mm)
Central plate of 4, low birefringence, blocks - one per quadrant, pores along the sutures. Medium sized (ca 4-8 µm)
1 central block
Single, low birefringence, central plate with 1 or 2 perforations. Small (ca 3-5 µm)
Single, low birefringence, central plate with indistinct cross-like central structure surrounded by multiple perforations. Medium sized (5-6 µm)
anomalous species
Holococcolith formed of four large, high birefringence, interlocking blocks forming both a rim and central cross. Medium sized (5-6 µm)
Specimens not identified to species level

Taxonomy:

Citation: Orastrum Wind & Wise in Wise & Wind, 1977
Rank: Genus
Type species: Orastrum asarotum Wind & Wise in Wise & Wind, 1977

Farinacci & Howe catalog pages: Orastrum *

Distinguishing features: Holococcoliths with narrow rim surrounding a central-area formed of 1-4 blocks. Typically non-cavate with no spine. Rim bright and central plate dark

Search data:
TagsLITHS: holococcolith, elliptical, CA: pores, bar, V-UNITS: V-prominent, R-UNITS: R-prominent, DETAILS: ca_disjunct, rim-unicyclic,
MetricsLith size: 3->11µm;
Sources: size range of included species
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Last occurrence (top): at top of Maastrichtian Stage (100% up, 66Ma, in Maastrichtian stage). Data source: Total of range of species in this database
First occurrence (base): in lower part of Aptian Stage (30% up, 122.3Ma, in Aptian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

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

Wise, S. W. & Wind, F. H. (1977). Mesozoic and Cenozoic calcareous nannofossils recovered by DSDP Leg 36 drilling on the Falkland Plateau, south-west Atlantic sector of the Southern Ocean. Initial Reports of the Deep Sea Drilling Project. 36(269-491): -. gs :: view :: open


nannotaxlogo400px

Orastrum compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 7-7-2020

Taxon Search:
Advanced Search

Short stable page link: http://mikrotax.org/Nannotax3/index.php?id=10821 Go to Archive.is to create a permanent copy of this page - citation notes



Comments (0)

No comments yet on this page. Please do add comments if you spot any problems, or have information to share

Add Comment

* Required information
1000
Captcha Image
Powered by Commentics