Caycedoa micheliorum

Bowman & Varol, 2021 Dec 29, 2022

Set number: 602

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10µm

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

Final Epithet

Caycedoa micheliorum Bowman & Varol, 2021

Basionym

Caycedoae micheliorum Bowman & Varol, 2021

Diagnosis

A moderate to large-sized and circular species of Caycedoa has one disc and a parallel-sided, wider than taller column, with a narrow central canal.

Etymology

After the Michel family of Ontario, N.Y. (USA).

Dimensions Of Holotype

Overall height: 5.27μm; Column height: 2.59μm, Column diameter: 4.90μm; Disc diameter: 7.25μm.

Description

Moderate to large size (6.0–9.0μm) and circular species of Caycedoae consisting of one disc and a column. The disc with a very slight depression on the proximal side appears slightly concave. The column is wider than taller and has a deep distal depression and is occupied by a narrow central canal. The number of disc segments and column segments is similar (about 26–40), and the disc segments are slightly broader than the column segments.

Optical Properties

The extinction lines appear dextrogyre on the distal/column side but laevogyre on the proximal/disc side. When viewed using a gypsum plate, the horizontal axis is observed within the blue sector on the distal side. In contrast, the vertical axis exists within the blue sector on the proximal side. In plan-view, the column displays the first-order yellow birefringence colour under polarised light, but the disc is non-birefringent. The disc and column are birefringent in the side-view.

Remarks

Caycedoa micheliorum displays a parallel-sided and non-notched column, whereas Caycedoa kaminadesneraidon has a notched column at the distal end. The column is wider than the taller in Caycedoa micheliorum, while the distally tapering column is taller than the wider in Caycedoa conicus and Caycedoa pattersonii.

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.