Daughter taxa (time control age-window is: 0-800Ma)
cross-shaped species
Nannotetrina spinosa Broadly square with elongations from the corners and shorter spines from the sides resulting in an stellate (eight-pointed) symmetrical outline.
Nannotetrina pappii Broadly square to cruciform with spinose projections resulting in a stellate (eight-pointed) asymmetrical outline.
Nannotetrina fulgens Large to very large Nannotetrina with arms that taper to a point.
Nannotetrina alata Large to very large Nannotetrina with long parallel sided free rays with blunt ray tips.
compact species, without free rays
Nannotetrina cristata Large three-dimensional Nannotetrina, broadly cross-shaped with curving arms that widen towards their ends and with inter-arm fill.
Nannotetrina plana Subcircular to broadly elliptical with a low basal disc crossed by broad, raised cross-bars.
Nannotetrina sp. Specimens which cannot be assigned to any established species - and some rarely cited species
Taxonomy:
Citation: Nannotetrina Achuthan&Stradner, 1969taxonomic rank: GenusType species: Nannotetrina fulgens (Stradner, 1960) Achuthan and Stradner, 1969 [Nannotetraster]Taxonomic discussion: The genus was originally called Nannotetraster but the type of that genus Discoaster staurophora is now considered to belong to Micula so the name Nannotetrina was substituted.
Distinguishing features: Parent taxon (Zygodiscaceae): Muroliths with rim formed from well-developed V- and variably developed R-units, with opposite imbrication directions, and central area structures that include disjunct transverse bars and diagonal crosses. R-units vestigial or not observed in several genera (Chiphragmalithus, Isthmolithus, Neococcolithes). This taxon: Typically large (>8 µm) cruciform nannoliths with high curving ridges running from the centre to ray tips.
Morphology: Relatively low birefringence in XPL, but the four rays are separate crystal units and go into extinction separately. Restricted to middle Eocene zones NP14b to NP16. Other nannofossils with similar appearance include four-rayed discoasters, e.g. Discoaster cruciformis and disarticulated cross-bars of Neococcolithes protenus. Size: Typically large (8-15 µm) and can be very large - up to 30 µm
See also:Neococcolithes - possible heterococcolith ancestor;
The morphological data given here can be used on the advanced search page. See also these notes
Geological Range: Notes: Largely restricted to middle Eocene zones NP15 to NP16. Last occurrence (top): at top of NP16 zone (100% up, 40.4Ma, in Bartonian stage). Data source: Total of ranges of the species in this database First occurrence (base): within NP14b subzone (46.29-47.84Ma, base in Lutetian stage). Data source: Total of ranges 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
Neptune data: This is a higher taxon page so Neptune data is not plotted. See also: customisable plot Parent: Zygodiscaceae
References:
Achuthan, M. V. & Stradner, H. (1969). Calcareous nannoplankton from the Wemmelian stratotype. In, Brönnimann, P. & Renz, H. H. (eds) Proceedings of the First International Conference on Planktonic Microfossils, Geneva 1967. Brill, Leiden, Geneva 1: 1-13. gs
Perch-Nielsen, K. (1985). Cenozoic calcareous nannofossils. In, Bolli, H. M., Saunders, J. B. & Perch-Nielsen, K. (eds) Plankton Stratigraphy. Cambridge University Press, Cambridge (1): 427-555. gs
Nannotetrina compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 6-10-2024
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