Heliotrochus Aubry 2014 - genus for disk-like Heliolithus species, type species H. kleinpellii
Distinguishing features: Parent taxon (Heliolithaceae): Discoidal discoasteralids with several distinct cycles including at least one that is birefringent. This taxon: Discoidal discoasteralids formed of two superposed birefringent cycles.
Morphology: The nanoltihs are formed of two prominent superposed cycles, both of which are strongly birefringent in plan view - the disk and column. The disk is broader than the column, when viewed from the disk side the nannolith appears unicyclic and the elements show anticlockwise obliquity. When viewed from the column side both cycles are visible, the column typically has a vertical edge and does not show imbrication, both cycles show clockwise obliquity.
In well preserved specimens/with favourable orientation a third cycle is visble between these two in at least some species (notably H. cantabriae), in the EM this cycle is visible at the base of the column.
Romein (1979) used crystallographic orientation to infer origin from Fasciculithus bitectus (= Lithoptychius s.l.) and suggested that the disk was distal.
The morphological data given here can be used on the advanced search page. See also these notes
Geological Range: Last occurrence (top): in upper part of Thanetian Stage (70% up, 56.9Ma, in Thanetian stage). Data source: Total of range of species in this database First occurrence (base): at base of Selandian Stage (4% up, 61.5Ma, in Selandian 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
Neptune data: This is a higher taxon page so Neptune data is not plotted. See also: customisable plot Parent: Heliolithaceae
References:
Aubry, M. -P. (2014). Cenozoic Coccolithophores: Discoasterales. Micropaleontology Press, American Museum of Natural History, New York. 1-400. gs
Bramlette, M. N. & Sullivan, F. R. (1961). Coccolithophorids and related nannoplankton of the Early Tertiary in California. Micropaleontology. 7(2): 129-188. 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 427-555. gs
Romein, A. J. T. (1979). Lineages in Early Paleogene calcareous nannoplankton. Utrecht Micropaleontological Bulletin. 22: 1-231. gsO
Heliolithus compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 26-3-2023
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