Orthorhabdus serratus

Bramlette & Wilcoxon, 1967 Feb 27, 2021

Set number: 1660

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10µm

ODP Leg 154, Hole 926A, Ceará Rise, western equatorial Atlantic.

in mobile mount

Set number: 1663

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10µm

DSDP Leg 25, Site 242, Mozambique Channel (Davie Ridge), Indian Ocean

Set number: 1662

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10µm

IODP Expedition 354, Hole U1451B, Bengal Fan, Indian Ocean

Set number: 1661

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10µm

DSDP Leg 25, Site 242, Mozambique Channel (Davie Ridge), Indian Ocean

Set number: 477

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10µm

Orthorhabdus serratus, Middle Miocene, DSDP Leg 25, Site 242, Mozambique Channel (Davie Ridge), Indian Ocean

Final Epithet

Orthorhabdus serratus Bramlette & Wilcoxon, 1967

Basionym

Orthorhabdus serratus Bramlette & Wilcoxon, 1967

Remarks

The mobile mount reveals that blades in Orthorhabdus are at equal angles to each other (plate 8, Figures 9-16 in Varol, 2025). The side view displays an inclined (oblique) extinction (Plate 9, Figures 3, 7, 9, 12-13, 16 in Varol, 2025); the extinction angle varies depending on how the “toe” of the hockey stick faces. The extinction angle is about 20° in the side view when the toe is directed to the left (Plate 9, Figures 3, 7 in Varol, 2025). In the plan view, Orthorhabdus appears in constant extinction (with the optic axis vertical to the microscope stage in this orientation, Plate 8 Figs. 1-3, 5-7 in Varol, 2025). Orthorhabdus serratus differs from the other taxa in the family Triquetrorhabdulaceae by having blades truncated at one end and pointed at the other. Orthorhabdus serratus also differs in that it has an inclined optic axis and exhibits length-slow (+) elongation at the side view.

References

Bramlette, M. N. & Wilcoxon, J. A. 1967. Middle Tertiary calcareous nannoplankton of the Cipero section, Trinidad, W.I. Tulane Studies in Geology and Paleontology 5: 93-131.

Gartner, S. 1967a. Calcareous nannofossils from Neogene of Trinidad, Jamaica, and Gulf of Mexico. University of Kansas Paleontological Contributions, Papers 29: 1-7.

Martini, E. 1965. Mid-Tertiary calcareous nannoplankton from Pacific deep-sea cores. Colston Papers 17: 393-411.

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

Taxonomy

Orthorhabdus

Biostratigraphy

Stratigraphic Range

Aquitanian - Serravalian

Age (Ma)

22.48 - 12.80

Holotype

Orthorhabdus serratus Bramlette & Wilcoxon, 1967

Early Miocene

Cipero Section, Trinidad