Nannotax3 - Mesozoic

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 2-4 blocks. Typically non-cavate with no spine. Rim bright and central plate dark

Daughter taxa: (blue => in age window 0-800Ma)
				4 central blocks
				Orastrum asarotum Central plate of 4 blocks - obliquely oriented
				Orastrum campanensis Central plate of 4 blocks - one per quadrant
				Orastrum porosuturalis Central plate of 4 blocks - one per quadrant, pores along the sutures
				1 central block
				Orastrum perspicuum Single low birefringence central plate with 1 or 2 perforations. Small (ca 3-4 µm)
				Orastrum robinsonii Single low birefringence central plate with indistinct cross-like central structure surrounded by multiple perforations. Medium sized (5-6 µm)
				anomalous species
				Orastrum colligatum Holococcolith formed of four large interlocking blocks forming both a rim and central cross.
				Orastrum sp. 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 2-4 blocks. Typically non-cavate with no spine. Rim bright and central plate dark

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:

Range-bar - range as quoted above, pink interval top occurs in, green interval base occurs in.
Triangles indicate an event for which a precise placement has been suggested
Neptune data: This is a higher taxon page so Neptune data is not plotted. See also: customisable plot Parent: Common genera

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

Orastrum compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 22-7-2019

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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

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