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Microfossil Mania!

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Another Interesting Ostracode From The Coralline Crag Formation



In picking out my sample of microfossils from the Middle Pliocene Coralline Crag Formation, Suffolk, England, I noted a few fragments of what appeared to be a species of the ostracode genus Pterygocythereis, a particularly spiny-looking genus of the family Trachyleberididae. I assumed it to be Pterygocythereis jonesi (Baird, 1850), the common species of the North Sea. As luck would have it, while finishing the picking of the last bit of the sample, up popped a complete valve, in almost perfect condition.

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To my surprise, it turned out not to be the common North Sea species; rather, it is Pterygocythereis siveteri Athersuch, 1972. The image does not do it justice, as even with image stacking software, the great length of the alae and the 3-D spininess are not very apparent. (Published dorsal views of the complete carapace are quite impressive!) Further cleaning of the specimen should greatly improve its appearance.

In the standard book on the recent Ostracoda of Great Britain, we find the following: "British records of P. siveteri are sub-Recent, and there are, as yet, no live records outside the Mediterranean." (Athersuch, Horne and Whittaker 1989: 146) Presence of this species thus provides further evidence that the Middle Pliocene sea around southern Great Britain was warmer than it is now, and that the ostracode fauna was essentially Lusitanian, characteristic of the modern Mediterranean Sea and of the Atlantic Ocean off the northwest coast of Africa.

The genus Pterygocythereis today is commonly encountered in the sublittoral zone, down to a depth of about 200 meters. Faunal studies of the Coralline Crag have suggested that it was deposited in a high energy environment with a maximum depth of about 20 meters, which seems to fit. However, this species is rather rare in the Coralline Crag, suggesting that it may not have been a member of the original, local biocoenosis.

Athersuch, J., D. J. Horne, and J. E. Whittaker, 1989, Marine and Brackish Water Ostracods, The Linnaean Society of London.

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This species is slightly larger than the average marine ostracode, and is roughly 1 mm. in length. Most recent ostracodes range between 0.5 and 1 mm., but a few are considerably larger. Some freshwater species are as much as 5 mm. in length, and there are some pelagic myodocopids that are reputed to be over an inch in length (30 mm.). Some of the leperditiids (Lower Ordovician to Upper Devonian) are also about this size.

Good hunting!

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Rumi: At 1mm, you might try using old fashioned technology ie a dslr with a bellows... fully extended and 50mm fix focus lens ( I use a Pentax F1.4 Takumar lens stopped down to F16 aperture and time exposure to increase depth of field... 6000k lighting and also mounting the camera on a copy stand with a precision focussing rail , remote shutter release and mirror lock up on camera also helps)....

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Great advice! Unfortunately, I don't have the financial wherewithal for such equipment at the moment. Perhaps in the not-too-distant future (big sigh). Retirement is good, but would be better with a little more income, ha ha!


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Another interesting post. :)

What methods are you employing for your cleaning process?

Edit: (Forgive my ignorance of the process, I get curious sometimes. :blush: )

Just wondering how you clean something that small? With chemicals or ultrasonic (mechanical) jewelry type cleaner?

Thanks Rumi!

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I've found a few very spiny ostracods from the Del Rio formation in Texas. Haven't taken the time to use CombineZ software on the fossil yet. Which stacking software do you use?

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Friable samples like this one will disaggregate fairly well by just boiling them with a little washing soda. Samples that are more solidly cemented usually require soaking in a petroleum-based solvent -- I use kerosene. After soaking for about a week, you decant off the kerosene, replace it with hot water, add a bit of no-suds detergent (to eliminate the remaining kerosene), and proceed to the boiling stage. This generally does the job. I have a good ultrasonic cleaner, which I loaned to a friend about 7 years ago. I guess it's time to ask for its return.....................


I also use CombineCP. It seems to do a reasonable job, and I like the fact that it's free!

Good hunting!


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Absolutely lovely! such detail! Im glad you have the cleaning process down to preserve such a tiny marvel.

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Thank you to all for your kind comments, they are much appreciated!



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