Quadrum blairiae

Set number: 2003

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10µm

Kystra, Czech Republic

Holotype

Set number: 2002

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10µm

Kystra, Czech Republic

Set number: 2001

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10µm

CB06 C-T, Cauvery Basin, India

Set number: 1999

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10µm

CB06 C-T, Cauvery Basin, India

Set number: 1999

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10µm

CB06 C-T, Cauvery Basin, India

Set number: 1998

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10µm

CB06 C-T, Cauvery Basin, India

Set number: 1997

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10µm

Ocal Creek, Colombia

Set number: 1996

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10µm

Ocal Creek, Colombia

In the mobile mount

Final Epithet

Quadrum blairiae Varol, 2025a

Basionym

Quadrum blairiae Varol, 2025a

Diagnosis

Large (8.0–15.0 μm) stellate species of Quadrum are characterised by long, strongly twisted segments along their joining surfaces that exhibit free length. The twisting can create a rotation angle of up to 45° between the upper and lower cycle segments. In specific profiles, the intense twisting combined with the concave-convex nature of both cycles can make the species superficially appear five-segmented.

Etymology

In honour of Dr S. A. Blair, Houston, Texas, USA, in recognition of her contributions to taxonomy and biostratigraphy of calcareous nannofossils.

Dimensions Of Holotype

Maximum diameter = 12.78 μm; diameter of the central area = 3.54 μm; free length of segments = 4.62 μm; Thickness = 3.08 μm.

Description

Optical Properties: Quadrum blairiae exhibits inclined extinction lines. It displays length-slow (+) elongation in the plan view and length-fast (-) elongation in the side view.

Remarks

Quadrum blairiae differs from Quadrum gartneri in its strongly twisted segments with free lengths. Quadrum gartneri has shorter segments joined along their entire length and appears square in the plan view.

References

Varol, O. 2025a. A practical guide to optical studies of calcareous nannofossils. Grzybowski Foundation Special Publication. 29: 1-222

Taxonomy

Quadrum

Quadrum blairiae

Biostratigraphy

Stratigraphic Range

Early Turonian - Late Turonian

Age (Ma)

93.82 - 89.39

Zone(s)

CC10 - CC13

Holotype

Quadrum blairiae Varol, 2025a

Late Turonian

Kystra, Czech Republic