Daughter taxa (time control age-window is: 0-800Ma)
Orthorhabdus serratus Elongate Orthorhabdus species - triangular in plan view, hockey-stick shaped in side view.
Orthorhabdus rugosus Orthorhabdus species with three blades of variable width; broadest blade usually rodded. The degree of birefringence shown depends on the orientation the nannolith is lying in.
Orthorhabdus striatus Orthorhabdus species similar to O. rugosus but with subsidiary ridges on one of the lateral blades.
Orthorhabdus finifer Horseshoe-shaped species of Orthorhabdus with short median blade and elongate curved lateral blades.
Orthorhabdus extensus Orthorhabdus species with one lateral blade very wide, with weak ridges.
Orthorhabdus sp. Specimens which cannot be assigned to established species
Taxonomy:
Citation: Orthorhabdus Bramlette&Wilcoxon, 1967 emend Young & Bown 2014Taxonomic rank: genusType species: Orthorhabdus serratus Bramlette and Wilcoxon, 1967Taxonomic discussion: Young & Bown (2014) redefined the genus to include species which had been included in Triquetrorhabdulus but in which the c-axis is perpendicular to the nannolith length. Raffi et al. (1998) and Lancis et al. (2022) discuss evolution from Orthorhabdus to Nicklithus, Amaurolithus and Ceratolithus
Distinguishing features: Parent taxon (Ceratolithaceae): Horseshoe-shaped rod-shaped nannoliths and simple hoop-coccoliths formed in one phase of life cycle, planolith heterococcoliths in the other. This taxon: Elongate nannoliths formed of three blades, with c-axis perpendicular to length. Usually curved and asymmetric. Shows low to moderate birefringence.
Morphology: The c-axis is perpendicular to the lenth of the nannolith. In most species the two lateral blades are wider than he median blade so the nannolith most commonly lies with the lateral blades flat and the median blade directed upward, in this orientation the nannolith shows no birefirngence, i.e. the c-axis is parallel to the median blade. In O. serratus the meian blade is wider than the lateral blades ands o the nannolith usually rests on its side and show significant birefringence.
The morphological data given here can be used on the advanced search page. See also these notes
Geological Range: Last occurrence (top): at top of NN12 zone (100% up, 5.1Ma, in Zanclean stage). Data source: Total of ranges of the species in this database First occurrence (base): within NN2 zone (19.00-22.82Ma, base in Aquitanian stage). Data source: Total of ranges of species in this database
Plot of occurrence data:
Range-bar - range as quoted above, pink interval top occurs in, green interval base occurs in.
Triangles indicate an event for which a precise placement has been suggested
Bramlette, M. N. & Wilcoxon, J. A. (1967b). Middle Tertiary calcareous nannoplankton of the Cipero section, Trinidad, W.I. Tulane Studies in Geology and Paleontology. 5: 93-131. gsO
Lancis, C., Tent-Manclús, J-E. & Flores, J-A. (2022). Origin and evolutionary trends of the Neogene genera Amaurolithus and Nicklithus (calcareous nannofossils). Marine Micropaleontology. 175: 1-15. gs
Raffi, I., Backman, J. & Rio, D. (1998). Evolutionary trends of tropical calcareous nannofossils in the late Neogene. Marine Micropaleontology. 35(1): 17-41. gs
Young, J. R. & Bown, P. R. (2014). Some emendments to calcareous nannoplankton taxonomy. Journal of Nannoplankton Research. 33(1): 39-46. gs
Young, J. R. (1998). Neogene. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series . 225-265. gs
Orthorhabdus compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 19-3-2025
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