Polycostella senaria
Set number: 46
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in mobile mount
Set number: 44
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in mobile mount
Set number: 40
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plan view
Set number: 38
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side view
Set number: 43
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in mobile mount
Set number: 45
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in mobile mount
Set number: 42
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Set number: 41
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plan view
Set number: 39
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plan view
Set number: 37
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10µm
Polycostella senaria Thierstein, 1971
Medium-sized (4.0–8.0 μm) nannoconid with six longitudinal ridges. The wall cycles are thin and low-angled, and the canal is very narrow. It is stellate in plan view, and the sutures between the segments meet at the periphery of the vertices. It is strongly birefringent in plan view, but weakly birefringent or non-birefringent at the side view. The height and width of specimens vary greatly but are often similar in size. The species' size follows a noticeable trend, as the height of the species decreases over time.
Polycostella senaria was originally described in the plan view. Therefore, its side view was unknown. Varol & Bowman (2019) proved that Nannoconus erbae is the side view of Polycostella senaria in mobile mount.
Thierstein, H.R., (1971): Tentative Lower Cretaceous Calcareous Nannoplankton Zonation. - Eclogae Geol. Helv., 64: 459–488.
Varol, O. & Bowman, A.R., (2019): Taxonomic revision of selected Late Jurassic (Tithonian) calcareous nannofossils and the application of mobile mounting - N. Jb. Geol. Paläont. Abh. 1 (2019), 1–23
Holotype
Polycostella senaria
Thierstein, 1971
Berriasian
Broyon (Ardeche), Southern France