Discoaster mediosus


Ancestry: Coccolithophores -> 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,

Short diagnosis: ≥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.


Taxonomy:

Citation: Discoaster mediosus Bramlette & Sullivan, 1961
Rank: Species
Variants: Discoaster minimus Sullivan 1964 - smaller and with fewer rays (Aubry 1984)
Notes & 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.

Farinacci & Howe catalog pages: Discoaster mediosus * Discoaster minimus *

Short diagnosis: ≥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.


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

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, 266 pp.

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


nannotaxlogo400px

Discoaster mediosus compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 20-8-2017

Taxon Search:
Advanced Search
AphiaID: 643452 Nomenclatural data on WoRMS
Go to Archive.is to create a permanent copy of this page - citation notes



Comments (2)

Sort By
Page 1 of 1
 
Gravatar
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

Gravatar
Rui da Gama

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

Page 1 of 1
 

Add Comment

* Required information
1000
Captcha Image
Powered by Commentics