Ostracod filled Elimia tenera microfossil thin section under the microscope

A new type of microscope slide arrived whilst I was away – a selection of three thin sections of microscopic fossils in rock.

This first one is Ostracod filled Elimia tenera, Laney Mbr. Green River Shale, Ecocene, Sweetwater County, Wyoming.



Naked eye image:


As you can see, the fossils are visible by eye without magnification.

From Wikipedia:

Ostracods, or ostracodes, are a class of the Crustacea, sometimes known as seed shrimp. Some 70,000 species have been identified, grouped into several orders. Wikipedia

Scientific name: Ostracoda
Class: Ostracoda; Latreille, 1802
Kingdom: Animalia
Phylum: Arthropoda
Rank: Class
Higher classification: Crustacean
Lower classifications: Podocopida, Myodocopina, Halocypridina

The following image of a modern Ostracod comes from Wikipedia:

Elimia tenera, formerly known as Goniobasis tenera, is an extinct species of freshwater snail with an operculum, in the aquatic gastropod mollusc family Pleuroceridae (Wikipedia).

Pictures of this snail can be found at http://rsquirespaleo.blogspot.co.uk/2016/08/elimia-tenera-commonly-misidentified.html

So, the shells of the snail were then filled with Ostracods – I assume after the former died – and the whole lot became fossilized.


LOMO MNC-1 polarising microscope images. Each caption lists the intermediate magnifying lens used – there is also a low power objective (I think 2x) and the magnification provided by the Bresser MikrOkular camera).

Ostracod-filled-Elimia-tenera-Wyoming-LOMO-Pol-microscope-0-6x-intermed-lens-260817-panorama-10-images.jpg (below – cross polarising filters – interestingly the crystals that form the fossilised snail shell (Elimia) appear to have different mineral content (appear pink/orange in image below) than those that form the fossilised Ostracod (blue) – I don’t know why that should be or which mineral these colours represent):

Ostracod-filled-Elimia-tenera-Wyoming-LOMO-Pol-microscope-2x-intermed-lens-260817.bmp (below):

Ostracod-filled-Elimia-tenera-Wyoming-LOMO-Pol-microscope-4x-intermed-lens-260817.bmp (below):

Ostracod-filled-Elimia-tenera-Wyoming-LOMO-Pol-microscope-7x-intermed-lens-showing-details-of–Elimia-shell-260817.bmp (below – also shows some birefringence in crystals making up matrix of rock around fossils – you can see here that the rock is composed of small crystals consistent with layers being laid down at bottom of ancient lake or sea):

Ostracod-filled-Elimia-tenera-Wyoming-LOMO-Pol-microscope-7x-intermed-lens-showing-whole-Ostracod-260817.bmp (below):


To obtain a higher power image, I changed over to the Zeiss Photomicroscope III for the next image, a panorama of 5 photos at 10x magnification (with Bresser MikrOkular camera):

Ostracod-x10-mag-Planapo-objective-Zeiss-Photomicroscope-III-260817-Panorama-5-photos.jpg (below):

I am quite impressed by the detail visible in the image!


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