Discoaster mediosus


Classification: ntax_cenozoic -> Discoasterales -> Discoasteraceae -> Discoaster -> D. nodifer group -> Discoaster mediosus
Sister taxa: D. cruciformis, D. colletii, D. gemmifer, D. mediosus, D. binodosus, D. nodifer, D. distinctus, D. septemradiatus, D. tanii, D. tani ornatus, D. istanbulensis, D. martinii, D. williamsii, D. backmanii, D. okadai

Taxonomy:

Citation: Discoaster mediosus Bramlette & Sullivan, 1961
Rank: Species
Variants: Discoaster minimus Sullivan 1964 - smaller and with fewer rays (Aubry 1984)
Taxonomic discussion: Discoaster mediosus and Discoaster binodosus intergrade but can be distinguished as follows: D. mediosus usually has ten rays or more, with free rays less than half the length of the central area; D. binodosus usually has 8 rays with longer free length and prominent lateral nodes and pointed ray tips.

Distinguishing features: ≥8 near-parallel-sided rays with rounded to pointed tips that radiate with little free length from a large circular central area. May show inter-ray ridges, a low central boss, and the development of nodes towards the ray tips.

Farinacci & Howe catalog pages: D. mediosus * , D. minimus *


Morphology: Typically 8-10 rays but can have more.

Search data:
TagsLITHS: nannolith-radiate, star-shaped, CROSS-POLARS: 1ou, V-prominent,
MetricsLith size: 11->21µm; Segments: 7->9;
Data source notes: size from OD & illustrated specs
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Last occurrence (top): within NP10 zone (54.17-55.86Ma, top in Ypresian stage). Data source: PRB entry to Nannotax
First occurrence (base): within NP7 zone (58.70-58.97Ma, base in Thanetian stage). Data source: PRB entry to Nannotax

Plot of occurrence data:

References:

Aubry, M. -P. (1984). Handbook of Cenozoic calcareous nannoplankton. Book 1: Ortholithae (Discoasters). Micropaleontology Press, American Museum of Natural History, New York. 1-266. gs

Bown, P. R. & Dunkley Jones, T. (2012). Calcareous nannofossils from the Paleogene equatorial Pacific (IODP Expedition 320 Sites U1331-1334). Journal of Nannoplankton Research. 32(2): 3-51. gs V O

Bown, P. R. (2005d). Palaeogene calcareous nannofossils from the Kilwa and Lindi areas of coastal Tanzania (Tanzania Drilling Project 2003-4). Journal of Nannoplankton Research. 27(1): 21-95. gs V O

Bown, P. R. (2010). Calcareous nannofossils from the Paleocene/Eocene Thermal Maximum interval of southern Tanzania (TDP Site 14). Journal of Nannoplankton Research. 31(1): 11-38. gs V O

Bown, P. R. (2016). Paleocene calcareous nannofossils from Tanzania (TDP sites 19, 27 and 38). Journal of Nannoplankton Research. 36(1): 1-32. gs V O

Bralower, T. J. & Self-Trail, J. (2016). Nannoplankton malformation during the Paleocene-Eocene Thermal Maximum and its paleoecological and paleoceangraphic significance. Paleoceanography. 31: 1-17. gs

Bramlette, M. N. & Sullivan, F. R. (1961). Coccolithophorids and related nannoplankton of the Early Tertiary in California. Micropaleontology. 7(2): 129-188. gs

Bybell, L. M. & Self-Trail, J. (1995). Evolutionary, biostratigraphic and taxonomic study of calcareous nanofossils from a continuous Palaeocene-Eocene boundary section in New Jersey. U.S. Geological Survey, Professional Paper. 1554: 1-36. gs V O

Perch-Nielsen, K. (1977a). Albian to Pleistocene calcareous nannofossils from the Western South Atlantic, DSDP Leg 39. Initial Reports of the Deep Sea Drilling Project. 39: 699-823. gs V O

Self-Trail, J. (2011). Paleogene Calcareous Nannofossils of the South Dover Bridge core, Southern Maryland (USA). Journal of Nannoplankton Research. 32(1): 1-28. gs V O

Shepherd, C. L. & Kulhanek, D. K. (2016). Eocene nannofossil biostratigraphy of the mid-Waipara River section, Canterbury Basin, New Zealand. Journal of Nannoplankton Research. 26(1): 33-59. gs V O

Theodoridis, S. (1984). Calcareous nannofossil biostratigraphy of the Miocene and revision of the helicoliths and discoasters. Utrecht Micropaleontological Bulletin. 32: 1-271. 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


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Discoaster mediosus compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 21-1-2021

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Short stable page link: http://mikrotax.org/Nannotax3/index.php?id=480 Go to Archive.is to create a permanent copy of this page - citation notes



Comments (1)

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Rui da Gama

"Short diagnosis: 8-10 near-parallel-sided rays" - several images provided herein show more than 10 rays

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Jeremy Young

good point - clearly the name is applied to forms with 11 or 12 rays, I will change the short diagnosis to >8 rays.

Thanks for pointing his out

Jeremy

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