Caycedoa yelpaze

Bowman & Varol, 2021 Dec 29, 2022

Set number: 600

1
2
3
4
5
6
7
8
9
10
11
12

10µm

Caycedoa yelpaze, Late Paleocene, DSDP Leg 25, Site 245, Mozambique Channel (Davie Ridge), Indian Ocean

Final Epithet

Caycedoa yelpaze Bowman & Varol, 2021

Basionym

Caycedoae yelpaze Bowman & Varol, 2021

Diagnosis

A moderate to large circular species of Caycedoa has one non-birefringent disc and a very low birefringent column. The column is embedded into the intra-disc area (i.e., nearly flush with the disc surface) and appears wedge-shaped, resembling hand-fans in the side-view.

Etymology

From Turkish yelpaze, hand-fan—referring to its hand-fan appearance.

Dimensions Of Holotype

Overall height: 5.42μm; Column height: 2.06μm, Column diameter: 6.32μm; Disc diameter: 9.45μm.

Description

Moderate to large size (6.0–9.0μm) circular species constructed of one disc and a very low column. The disc is flat to very slightly concave, with a minor depression on the proximal side (best seen in the side-view). The shallow column appears like a hand-fan, does not extend above the disc parameter (i.e. lacks free length), and contains a narrow central canal. The disc and column consist of a similar number of segments (about 20–26), and the disc segments are much broader than the column segments.

Optical Properties

The extinction lines are dextrogyre on the distal/column side, whereas the extinction lines are laevogyre on the proximal/disc side. When viewed using a gypsum plate, the horizontal axis relates to the blue sector on the distal side, but the vertical axis relates to the blue sector on the proximal side. In the plan view, the column displays a first-order yellowish-white birefringence colour, whereas the disc appears non-birefringent under polarised light. The disc and column are birefringent in the side-view.

Remarks

Caycedoa yelpaze differs from other species of Caycedoa by having a very low column that does not extend above the disc parameter. Caycedoa yelpaze possesses a hand-fan-shaped column that lacks free length, a vital characteristic separating the species from Caycedoa kaminadesneraidon and other Caycedoa species. There are fewer segments in the disc and column of Caycedoa yelpaze compared to other species of Caycedoa.

References

Bowman, A. R. & Varol, O. 2021. A Taxonomic Revision of Heliolithaceae - Applications in Resolving the Problematic Calcareous Nannofossil Biostratigraphy of the Paleocene. In: M. Montenary, M. (Ed.). Calcareous nannofossil biostratigraphy of the Stratigraphy and timescales. 6: 43-223.