[coccoliths] Unidentified calcareous nannofossil

[Jeremy Young]

Hi

Nice images and interesting nannofossils. I guess there are rwo nanoliths here. At the bottom right  are several photos of a specimen which looks close to finifer. The other photos are the mystery nannofossil which I agree does not look like anything described before. It is a bit tricky working out what we have here without a caption but I see 6 specimens each illustrated by two or more images, and a further 10 specimens illustrated by one image each. So, 16 specimens in total with a rather consistent morphology. This is quite enough to describe a new species and it probably should be in a new genus.

    
 Lancis et al. 2022, & 2024 illustrate a lot of diverisity in the  group, building on previous work of Theodoridis 1984 and Raffi et al 1998. However, they do not illustrate anything directly resembling your speciemn s. 

Jeremy 

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.
Lancis, C., Tent-Manclus, J-E & Flores, J-A (2024). Origin and evolution of the Neogene calcareous nannofossil Ceratolithus. Marine Micropaleontology. 186: 1-18. 
Raffi, I., Backman, J. & Rio, D. (1998). Evolutionary trends of tropical calcareous nannofossils in the late Neogene. Marine Micropaleontology. 35(1): 17-41
Theodoridis, S. (1984). Calcareous nannofossil biostratigraphy of the Miocene and revision of the helicoliths and discoasters. Utrecht Micropaleontological Bulletin. 32: 1-271.


x	x	x	x	x	1
1	1	1	1	x	x
x	2	2	2	2	2
3	5	4	4	4	4
4	3	5	g	g	g	

a grid representing where the multiple images of specimens are = x - single image of a specimen 1-> 5 multiple images of single specimens; g groups of 4 images, inc those of O. finifer.
Speimens 1,2,4 &5 are all the same way up. Specimen 3 is the other way up.





> On 6 May 2026, at 14:55, Andre Gatto <andregatto at geologia.ufrj.br> wrote:
> 
> ⚠ Caution: External sender
> 
> 
> Dear colleagues,
> 
> I hope this message finds you well.
> 
> I am writing to request your input regarding an unidentified calcareous nannofossil that I have been consistently observing in samples assigned to the Late Miocene (NN11). The specimens were recovered from marine sediments (offshore Brazil, SW Atlantic), and have been analyzed under cross-polarized light microscopy. I have attached a set of photomicrographs illustrating multiple orientations and preservation states.
> 
> I have been considering possible affinities with Orthorhabdus finifer, as well as Orthorhabdus extensus and Ceratolithus vidalii, but none provided a satisfactory match.
> 
> I would greatly appreciate any insights, suggestions, or references that might help clarify its taxonomic affinity.
> 
> Thank you very much for your time and expertise.
> 
> Best regards,
> André Luiz Gatto Motta
> 
> <NN-UNKN-2026.jpg>
> 
> --
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