It is preserved in Late Cretaceous amber and seems mineralized, maybe siliceous. Diameter is 100 µm.
Nice that you suggest a phytolith, my first idea was a radiolarian (hard to believe in amber, but I already found some centric diatoms in this amber, so marine protozoans are possible); then I found phytoliths of another type and I changed my mind about the present inclusion. You seem to corroborate my view. Thanks Matt.
Diatoms also occur in freshwater. Is the amber deposit closely associated with marine sediments? If so, radiolarian could be introduced as transported clasts.
yes, it looks like a prasinophyte, therefore my question about the size!
Thomas: the diameter is ca. 100 µm (mentioned in my question). Prasinophytes are not siliceous, are they? Though I'm not sure this inclusion is siliceous...
Pierre Zippi: the diatoms I have found in this amber are centric ones, assignable to the marine genus Corethron. And yes, the amber was found in a shale deposited in an estuarine, marine-dominated environment.
I will say rather phytolith, see figures in http://www.pnas.org/content/106/13/5019.full
why does it need to be siliceous? I am more thinking about organic. central body and veil around. Pterospermella would make it marine-brackishwater something like this
http://fossiilid.info/1514
Francesca Sangiorgi: organic protists in amber are usually preserved like insect cuticle, i.e. with their 'exoskeleton' light to dark brown in color, while mineralized skeletons appear translucent/cristalline, exactly like the present inclusion. I have both diatoms and dinoflagellates in other pieces of French amber, and the new fossil is more similar to the cristalline aspect of the diatom frustules.
Sorry for the low magnification and poor viisbility, I do not have better photos at present as the sample is in loan for the study of the fly in syninclusion
The structure looks too small to be midge eggs (eggs are not uncommonly seen near rear end of female nematocerans in amber), so why is it not just a liquid exsudate from the insect anus?
Could it be a Heliozoan? These protists would fit the size, have siliceous skeletons and occur in freshwater environments.
Heliozoa too fragile for this, but maybe one of the testate amoebae. I've seen plenty of testate amoebae in amber. One should not exclude that it could be junk (non-biological).
you will have to zoom it (high magnification) for correct identification. no other way Dr. Vincent
could you take a picture from an other angle? at the present position it is unclear and to say any thing will be on air.
Vartika Singh, Habib Alimohammadian: you're right of course, but as I said in a previous answer yesterday this sample is currently in loan for the study of the fossil fly preserved together in this piece. I will need to get it back to take some better photos at higher magnification. At the moment this is the only photo I have and I agree this is not enough for a clear ID.
It may be a part of the internal tissues of the insect especially it is now situated at the end of the tail beside an isloated part of the wing.
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