Discoaster altus


Ancestry: Coccolithophores -> Discoasterales -> Discoasteraceae -> Discoaster -> D. brouweri group -> Discoaster altus
Sister taxa: D. triradiatus, D. tamalis, D. asymmetricus, D. altus, D. neorectus, D. brouweri, D. calcaris, D. braarudii, D. brouweri–like preservational morphotypes,

Short diagnosis: 6 rayed with complanate rays; very large stellate proximal boss; and small distal boss.


Taxonomy:

Citation: Discoaster altus Muller, 1974
Rank: Species
Synonyms: D. tristellifer Bukry, 1976. As explained by Young (1998) D. tristellifer and D. altus were described from the same material, DSDP Site 242 Core 3 Section 1, but without reference to each other. Both species were described as 6-rayed discoasters with very large proximal bosses and complanate rays. Re-examination of this material reveals, unsurprisingly, that it contains only one such species. The description of Bukry (1976), based on light microscopy, is more complete, since it mentions the smaller, but very distinct, distal knob. The description of Muller (1974), however, has priority so the correct name is D. altus. Bukry (1981) provide further illustrations and description.
Catinaster altus (Muller 1974) Perch-Nielsen 1984

Farinacci & Howe catalog pages: Discoaster altus * Discoaster tristellifer *

Short diagnosis: 6 rayed with complanate rays; very large stellate proximal boss; and small distal boss.


Morphology remarks: Both bosses are well-developed as can be seen by focussing up through the specimens but the boss on one side is much larger than the other. The larger boss is considered proximal since the points of the star are directed along the rays rather than between them. Raytips on well-preserve specimens may have notch at the end.

Geological Range:
Notes: A short-ranging and highly distinctive species, most records from the Indo-Pacific.
Last occurrence (top): within NN15 zone (3.70-3.92Ma, top in Zanclean stage). Data source: Young 1998
First occurrence (base): within NN14 zone (3.92-4.13Ma, base in Zanclean stage). Data source: Young 1998

Plot of occurrence data:

References:

Bukry, D., (1981). Pacific coast coccolith stratigraphy between Point Conception and Cabo Orientes, Deep Sea Drilling Project Leg 63. Initial Reports of the Deep Sea Drilling Project, 63: 445-471.

Bukry, D., (1976). Coccolith stratigraphy of Manihiki Plateau, Central Pacific, Deep Sea Drilling Project Site 317. Initial Reports of the Deep Sea Drilling Project, 33: 493-501.

Müller, C., (1974). Calcareous nannoplankton, Leg 25 (Western Indian Ocean). Initial Reports of the Deep Sea Drilling Project, 25: 579-633.

Perch-Nielsen, K., (1984). Validation of new combinations. Newsletter of the International Nannoplankton Association, 6(1): 42-46.

Young, J.R., (1998). Neogene. In: Bown, P.R. (Editor), Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publications Series. Chapman & Hall, London, pp. 225-265.


Nannotax3 - Coccolithophores - Discoaster altus by: Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 26-3-2017

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Comments (1)

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Mike Styzen (Noble Energy, US)
It would be nice to include the original description of D. tristellifer here if it is available from the Catalog. Maybe you could post it with a circle with a slash superimposed like a no smoking sign...
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Jeremy Young (NHM, UK)
good point Mike, I will try to get this done (not just now though, as I am on a ship with slow internet connection). Actually though there is no need for a warning sign against Bukry's descrition of D. tristellifer, I would argue that it is a better descrition than that of D. altus; the name does not have does not priority but the description and illustration are still first rate.

[NB The type illustrations can now be seen on this page, by clicking the Farinacci catalog page link - JRY March 2014] 
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