Orastrum
Classification: ntax_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) |
 |  | | | Orastrum schollei
|
| 4 central blocks |
 |  |  |  | Orastrum asarotum
Central plate of 4, high birefringence blocks - obliquely oriented; central pore. Medium sized (ca. 4-6 µm)
|
 |  |  |  | Orastrum campanensis
Central plate of 4, low birefringence, blocks - one per quadrant. Large (ca 8-11 mm)
|
 |  |  |  | Orastrum porosuturalis
Central plate of 4, low birefringence, blocks - one per quadrant, pores along the sutures. Medium sized
(ca 4-8 µm)
|
| 1 central block |
 |  |  |  | Orastrum perspicuum
Single, low birefringence, central plate with 1 or 2 perforations. Small (ca 3-5 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, high birefringence, interlocking blocks forming both a rim and central cross. Medium sized (5-6 µm)
|
 |  |  |  | Orastrum sp.
Specimens not identified to species level
|
Taxonomy:
Citation: Orastrum Wind & Wise in Wise & Wind, 1977Rank: GenusType 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:
| Tags | LITHS: holococcolith, elliptical, CA: ca_disjunct, pores, bar, CROSS-POLARS: rim-unicyclic, V-prominent, R-prominent, |
| Metrics | Lith size: 3->11µm;
Data source notes: 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:
- 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 V O
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 V O
