Umbellosphaera sp. Specimens which cannot be assigned to established species
Taxonomy:
Citation: Umbellosphaera Paasche in Markali & Paasche, 1955Rank: GenusType species: Coccolithus tenuis Kaptner, 1937Synonyms: Ellipsodiscoaster Boudreaux and Hay, 1969
Distinguishing features: Parent taxon (Umbellosphaeraceae): Placolith-like with distal shield much larger than proximal, predominantly formed from R-units, V-units vestigial. This taxon: Coccoliths trumpet-shaped
Morphology: Coccoliths trumpet-shaped. Main part is R-unit, with narrow V-unit round base, but only tube is thick enough to give strong birefringence. In cross polars distal shield usually shows low birefringence (as it is very thin), whilst tube is highly birefringent (since it is muchthicker than the shield). As a result Umbellosphaera coccoliths resemble a small Reticulofenestra with a wide dark rim.
Coccolith types: (based on Kleijne 1993): 1. Macrococcoliths: large liths with broad rims, forming outer surface of coccosphere; central area sub-circular. 2. Micrococcoliths: small liths with narrow rims, only visible on broken coccospheres; Central area elliptical, rims often with less ornament than on the macrococcoliths. Thistye intergrade so it is porbbly more useful to consider the coccliths as varimorohic. Size:
Ecology & Biogeography: The genus is characteristic of oligotrophic surface waters. Phylogenetic relations: The coccoliths are clearly heterococcoliths, but show no obvious affinities to any of the major groups. The absence of a well developed V-unit cycle makes affinity with the Coccosphaerales or Zygodiscales unlikely and the absence of T-unit radial laths separates them from the Syracosphaerales. An alternative possibility suggested by the dominant development of the R-units is that they are highly modified Noelaerhabdaceae. This is weakly supported by the rare occurrence of malformed E. huxleyi specimens, which resemble Umbellosphaera, and by the general similarity of the cross-polarised light interference figure of Umbellosphaera coccoliths to those of Noelaerhabdaceaen coccoliths.
The morphological data given here can be used on the advanced search page. See also these notes
Geological Range: Last occurrence (top): Extant. Data source: Total of range of species in this database First occurrence (base): in upper part of Zanclean Stage (82% up, 3.9Ma, in Zanclean stage). Data source: Total of range of species in this database
Plot of occurrence data:
Range-bar - range as quoted above, pink interval top occurs in, green interval base occurs in.
Triangles indicate an event for which a precise placement has been suggested
Boudreaux, J. E. & Hay, W. W. (1969). Calcareous nannoplankton and biostratigraphy of the late Pliocene-Pleistocene-Recent sediments in the Submarex cores. Revista Española de Micropaleontología. 1(3): 249-292. gsO
Markali, J. & Paasche, E. (1955). On two species of Umbellosphaera, a new marine coccolithophorid genus. Nytt Magasin for Botanikk. 4: 95-100. gs
Umbellosphaera compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 27-9-2022
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