S. dissimilis group


Classification: Coccolithophores -> Discoasterales -> Sphenolithaceae -> Sphenolithus -> S. dissimilis group
Sister taxa: S. capricornutus group, S. dissimilis group, S. moriformis group, S. heteromorphus group, S. predistentus group, S. furcatolithoides group, S. radians group, S. conspicuus group, S. sp.,

Daughter taxa: (blue => in age window 0-800Ma)
cylindroconical with short spine and high base
cylindroconical with long spine and high base
cylindroconical with long spine and low base
Distinctive triangular outline and very short multipartite spine. (NB The name tininnabulum means small bell and describes the shape).
Cylindroconical with short spine and low base (like S. tintinnabulum but less triangular)
cylindroconical with long spine, high base and a distinct central bulge

Taxonomy:

Citation: Sphenolithus dissimilis group
Rank: species group
Notes & discussion: The set of species included here closely follows that of Bergen et al. (2017), but with the addition of S. tintinnabulum (Bergen et al. 2017 exclude S. tintinnabulum on the grounds that it has a monocrystalline spine but the holotype has a compound spine, as stated in the type description of Maiorano & Monechi 1997).

Distinguishing features: Bases cylindrical or conical, compound apical spine

Farinacci & Howe catalog pages: dissimilis group [no catalog entry yet]


Morphology remarks: Sphenoliths with bases that are either cylindrical or slightly conical (minimal taper distally) are placed within this group (Table 4). In specimens with high bases, the extinction lines cross and then parallel the lateral periphery (S. dissimilis, S. disbelemnos); if their bases are low, the extinction lines cross and continue to diverge (S. procerus, S. paratintinnabulum). All five species included in this group have compound apical spines. Sphenolithus cometa is closely related to members of this group (S. procerus and S. dissimilis), but is placed within the biconical Group 3 because of its narrowly divergent spine. [Bergen et al. 2017].

Search data:
Tags
MetricsLith size: 0->0┬Ám;
Sources:
The morphological data given here can be used on the advanced search page. See also these notes

See also: Sphenolithus belemnos - probably directly related, but with monocrystalline spine;

Geological Range:
Notes: This group of sphenolths is characteristic of the Early Miocene in NN3 it gives rise to S. belemnos and then disappears (subsequent sphenolith assemblages are dominated by S. heteromorphus).
Last occurrence (top): in upper part of Burdigalian Stage (56% up, 17.9Ma, in Burdigalian stage). Data source: Total of range of species in this database
First occurrence (base): in lower part of Bartonian Stage (22% up, 40.4Ma, in Bartonian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

Bergen, J. A., de Kaenel, E., Blair, S. A., Boesiger, T. M. & Browning, E. (2017). Oligocene-Pliocene taxonomy and stratigraphy of the genus Sphenolithus in the circum North Atlantic Basin: Gulf of Mexico and ODP Leg 154. Journal of Nannoplankton Research. 37(2-3): 77-112. gs

Maiorano, P. & Monechi, S. (1997). New Early Miocene species of Sphenolithus Deflandre, 1952 from the North Atlantic Ocean. Journal of Nannoplankton Research. 19(2): 103-107. gs


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S. dissimilis group compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 20-9-2019

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Short stable page link: http://mikrotax.org/Nannotax3/index.php?id=1539 Go to Archive.is to create a permanent copy of this page - citation notes



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