D. araneus group


Classification: Coccolithophores -> Discoasterales -> Discoasteraceae -> Discoaster -> D. araneus group
Sister taxa: D. brouweri group, D. pentaradiatus group, D. quinqueramus group, D. variabilis group, D. exilis group, D. musicus group, D. deflandrei group, D. nodifer group, D. lodoensis group, D. multiradiatus group, D. araneus group, D. sp.,

Daughter taxa: (blue => in age window 0-800Ma)
15-20 rays. Large to very large, typically asymmetric, rosette-shaped discoaster with a tall narrow stem on one side and 15-20 irregularly shaped curving rays that are free rays for around half the diameter.
10-14 rays.
7-9 rays. Large to very large, typically asymmetric discoaster with a prominent boss on one side and 7-9 tapering rays that have variable curvature and free length (1/3 to 2/3 of total ray length).
6 or less rays; Typically six rayed, stellate (star-shaped) discoaster with relatively long, tapering free rays comparable in length to the central area width. The central area has inter-ray ridges and a small but prominent central boss on one side. The rays look rather ragged and sometimes appear to be asymmetrically arranged.

Taxonomy:

Citation: D. araneus group
Rank: species group
Notes & discussion: Grouping suggested during the 2015 Discoaster workshop in Plymouth. The taxa included here appear to be malformed representatives of different discoaster types so it is probably not a useful phylogenetic grouping but for identification it is clearly convenient.
UPDATE - Bralower and Self-Trail (2016) examined this group in detail in expanded PETM sequences on the New Jersey margin. They conclude that they are all varieties of D. salisburgensis and propose new combinations on this basis.

Distinguishing features: Irregular "malformed" discoasters characteristic of the PETM excursion

Farinacci & Howe catalog pages:

See also: Discoaster salisburgensis - regular counterpart to these morphologies according to Bralower & Self-Trail (2016);

Search data:
TagsLITHS: nannolith-radiate, star-shaped,
CSPH: not known, V-UNITS: all, R-UNITS: none, DETAILS: 1ou,
MetricsLith size: 10->25µm;
Sources:
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Notes: These taxa are characteristic of the unusual assemblages developed during the Paleocene-Eocene Thermal maximum (PETM)
Last occurrence (top): in lower part of Ypresian Stage (22% up, 54.2Ma, in Ypresian stage). Data source: Total of range of species in this database
First occurrence (base): in upper part of Thanetian Stage (62% up, 57.2Ma, in Thanetian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

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


nannotaxlogo400px

D. araneus group compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 6-12-2019

Taxon Search:
Advanced Search

Short stable page link: http://mikrotax.org/Nannotax3/index.php?id=418 Go to Archive.is to create a permanent copy of this page - citation notes



Comments (0)

No comments yet. Be the first!

Add Comment

* Required information
1000
Captcha Image
Powered by Commentics