Cyclagelosphaera paez-rayesii
Set number: 1744
-
1
-
2
-
3
-
4
-
5
-
6
-
7
-
8
-
9
-
10
-
11
-
12
-
13
-
14
-
15
-
16
-
17
-
18
-
19
-
20
-
21
-
22
-
23
-
24
10µm
Holotype, in the mobile mount
Cyclagelosphaera paez-rayesii Varol, 2025
Circular placoliths have equal-diameter, single-tiered concave-convex distal and proximal shields, along with a double tube cycle that protrudes distally, leaving a narrow open central area.
In honour of Dr M. Paez-Rayes, Bogota, Colombia, in recognition of his contributions to the stratigraphy and geology of Colombia.
Diameter of shields = 6.76 μm; Width of tube cycle = 0.97 μm; Width of central opening = 1.06 μm; Thickness = 3.14 μm.
Optical Properties: In the plan view, all except the outer tube cycle exhibit inclined extinction lines, displaying length-fast (-) elongation. The extinction lines are dextrogyre on the distal side, and their typical angles are typically around 73° on the distal shield and 53° on the tube cycles on the distal side. These measurements of the tube cycle differ from those of Cyclagelosphaera species from the Cretaceous period. In the plan view, the outer tube cycle remains in constant extinction because the optic and c-axis are vertical relative to the microscope stage.
Cyclagelosphaera paez-rayesii is the only species of Cyclagelosphaera with an open central area in Paleocene sediments. Cyclagelosphaera jiangii and Cyclagelosphaera lacuna also have an open central area but are restricted to Early Cretaceous and Jurassic sediments, respectively.
Varol, O. 2025a. A practical guide to optical studies of calcareous nannofossils. Grzybowski Foundation Special Publication. 29: 1-222
Holotype
Cyclagelosphaera paez-rayesii
Varol, 2025
Selandian
DSDP Leg 25, Site 245, Mozambique Channel (Davie Ridge), Indian Ocean