Nannotax3 - ntax_cenozoic - Minylitha convallis

Citation: Minylitha convallis Bukry 1973

Taxonomic discussion:
The affinities of this species are unknown, but since it is formed of a single crystallographic unit it may be related to the Triquetrorhabdulaceae. The crystallographic orientation is wrong for it be related to Florisphaera.

Morphology: Plate-like rhomboidal nannoliths, with a raised rim on both sides. Acts as a single crystallographic unit with the optic axis nearly perpendicular to the plate.
Remarks: In plan view M. convallis shows only low birefringence and is easily overlooked. The dog-bone like side view, first described by Theodoridis (1984), is more distinctive and makes identification unambiguous. Can also give a Y-shaped cross-section - see comments below.

Size: : 4-8 microns long, usually 4-6 microns.

Geological Range:
Notes: This species is often abundant but distribution is rather sporadic.
Last occurrence (top): in upper part of NN11a subzone (70% up, 7.7Ma, in Tortonian stage). Data source: Young 1998, position in zone estimated from fig 8.1, see also Raffi et al. 2006
First occurrence (base): in upper part of NN9 zone (70% up, 9.8Ma, in Tortonian stage). Data source: Young 1998, position in zone estimated from fig 8.1, see also Raffi et al. 2006

References:

Browning, E., Bergen, J. A., Blair, S. A., Boesiger, T. M. & de Kaenel, E. (2017). Late Miocene to Late Pliocene taxonomy and stratigraphy of the genus Discoaster in the circum North Atlantic Basin: Gulf of Mexico and ODP Leg 154. Journal of Nannoplankton Research. 37(2-3): 189-214. gs V O

Bukry, D. (1973c). Coccolith stratigraphy, eastern equatorial Pacific, Leg 16, Deep Sea Drilling Project. Initial Reports of the Deep Sea Drilling Project. 16: 653-711. gs V O

de Kaenel, E. & Villa, G. (1996). Oligocene-Miocene calcareous nannofossil biostratigraphy and paleoeecology from the Iberian Abyssal Plain. Proceedings of the Ocean Drilling Program, Scientific Results. 149: 79-145. gs V O

Perch-Nielsen, K. (1977a). Albian to Pleistocene calcareous nannofossils from the Western South Atlantic, DSDP Leg 39. Initial Reports of the Deep Sea Drilling Project. 39: 699-823. gs V O

Theodoridis, S. (1984). Calcareous nannofossil biostratigraphy of the Miocene and revision of the helicoliths and discoasters. Utrecht Micropaleontological Bulletin. 32: 1-271. gs V O

Young, J. R. (1998). Neogene. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series. 225-265. gs V O

Comments (1)

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Mike Styzen (Noble Energy, US)

in addition to the perspectives addressed above there is another common view which you can encounter, that ie a Y shape. When I'm training people to look for this species I talk about the I the Y and the pie!

9th March 2011 12:00am

Yes, but often it is more pronounced than what is illustrated in those photos.

Jeremy Young (NHM, UK)

by the Y view do you mean the ones in the lower images of image 6-29 (LM image with side views)?

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Tags	LITHS: nannolith-other, quadrate, CROSS-POLARS: 1ou, V-prominent,
Metrics	Lith size: 4->8µm; Data source notes: lith size from OD & illustrated specimens

Minylitha convallis

References:

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