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Microfossils of the Permian Florena Shale: Part 2

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Rumi

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In this second entry I would like to show well-preserved specimens of two ostracodes: the very long-ranging taxon Amphissites centronotus (Ulrich and Bassler, 1906), and the Permian taxon Cornigella parva Kellett, 1933.  The former belongs in the family Amphissitidae, while the latter is placed in the family Drepanellidae.

 

A_centronotus.jpg

 

This specimen is a relatively late instar, but not fully mature, as final instar specimens average about 50% larger.  The species is very easy to recognize, the very large and prominent central node being quite distinctive.  Additionally, there are two strong ventral flanges, the inner flange curving upward to the anterior cardinal angle.  There is a fairly strong dorsal ridge, the ends curving abruptly downward to form anterior and posterior ridges, the former being the longer of the two.  The flanges and ridges are considerably weaker on early instars, but the prominent central node is still unmistakable.  So far as I am aware, this taxon occurs throughout the Pennsylvanian (and perhaps earlier), and disappears by mid-Permian time, a range in excess of 100 Ma.  It has been assumed that this species was a free-swimming benthic form, as the prominent flanges would not be well-suited to an infaunal mode of life.

 

C_parva.jpg

 

Betty Kellett described two species of the genus Cornigella from the Fort Riley Limestone of the Chase Group, higher in the Permian section of Kansas: Cornigella parva Kellett 1933, and Cornigella binoda Kellett 1933.  They differed in the number of lateral nodes, the former species having a larger number of nodes, while in the latter species only the two prominent dorsal nodes were present.  However, Kellett noted that her specimens showed considerable variation, which she attributed to poor preservation and diagenetic crushing.  She went so far as to suggest that the two described taxa might actually be the same.  Looking at Florena specimens, which are well-preserved complete carapaces, I would agree with her suggestion.  The lateral nodes exhibit varying degrees of development; although the two dorsal nodes are always strongly developed, the ventral and anterior nodes may be considerably weaker.  The specimen shown here is very well-preserved, and the full (?) complement of lateral nodes is clearly represented.  (Note that, since we are looking at a complete carapace, the posterior dorsal node of the right valve is also obvious, as is a hint of the anterior dorsal node.)  This specimen is also of interest, in that it shows a lot of the surface sculpturing, not too obvious on other specimens.  I have chosen the name C. parva for this taxon, as Kellett's description appears first on the page, and should thus have priority.

 

I have not seen the description or illustrations of the generotype Cornigella minuta Warthin, 1930, which was described as having eight "prominent spines", one projecting well above the hinge line.  Type specimens were from the Pennsylvanian Wetumka Formation of Oklahoma.  I would follow Kellett's judgement in deciding that the Permian taxon was not conspecific with that of Warthin.

 

I had hoped to illustrate a perfect carapace of Ectodemites pinguis (Ulrich and Bassler, 1906) from the Florena, which I had temporarily stored in a small black plastic tray (the lid of a micromount box) on my desktop.  Unfortunately, when I went to retrieve it for photography, it had simply disappeared -- even though I thought it to be well covered!  Now it's fodder for the vacuum cleaner, one of the hazards of microfossil collecting................!

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Excellent photos and descriptions.  Thanks for posting this. 

Could you give a brief run down on how you collected and photographed these?

I have found ostracods but have a miserable time handling and photographing them

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Squali: I did not collect this material myself -- I fairly regularly purchase small samples of washed residues from one or the other of the two commercial dealers I know of.  They are very cheap, and much more economical than the time and effort required to visit these localities myself.  At my age, I probably wouldn't even make it, ha ha!

 

As for study and photography, I'm happy to share.  I generally pick specimens with a standard, wood-handled biological dissecting needle.  I like the ones with a 45-degree bend, as you can use it as a "rake" to move waste material.  The idea is that the needle develops just enough static attraction to get the specimen to adhere to the tip.  If it develops too much, ground it temporarily on a bit of rubber -- a rubber cork works nicely.  To safely move specimens to a different container or microscope slide, the good old moistened sable brush (size 000) works very well.  For temporary storage of specimens for photography, I use the lids of standard, black micromount boxes -- but as mentioned, these must be very securely covered when not in use!

 

I photograph specimens through an old Leitz RS stereo microscope with a Tucsen 5 mp camera replacing one eyepiece.  This allows incident light images with 16 - 160X magnification.  (The ostracode images were at a magnification of ~60X.)  The software that runs the camera also allows quite accurate measurement of specimens.  If I need to use transmitted light, I put the specimen in a standard well-slide with distilled water or alcohol, add a cover slip, and use the same camera on the third port of my biological/clinical microscope.  I get magnifications of 100-1000X with this setup, which I need for my studies of fossil diatoms, and I'm able to use oblique lighting (both lateral and circular), as well as phase contrast.  The avatar that accompanies this message, an image of a specimen in the genus Stephanopyxis,  was made at 200X.  I use image-stacking software, the absolutely free and superb CombineZP.  To make photographs with incident light, I place the specimens on a small, circular plate of black glass.  This plate rests in a Stender dish, which is massive enough to facilitate manipulation under the 'scope.  To manipulate standard micropaleontology slides, I rest the slide across the dish, then move only the latter.  (I have a fairly severe intentional tremor, and trying to move anything as light as a cardboard slide under the 'scope is simply impossible for me -- I can't locate ANYTHING without the heavy glass dish, which resists my hand vibrations quite nicely.)  Photos made on the black circle of a micropaleontology slide will also work, although the background is pretty rough.  That can be corrected with photo editing software, of course.  I also use such software to adjust brightness, contrast, and (to a very limited extent) sharpness.  And I almost always greyscale my images, except for some diatom photos, where diffraction colors can be very helpful for identification to species in some genera.

 

Hope this is helpful to you!

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Rumi-

Thank you so much for taking the time to clearly describe your processes.  Hand shaking is a problem I've had to work on as well.  I'm using a B&L stereozoom 4.

I can get about 100x with the 15x eyepiece  but haven't found the right camera to match the eye piece.  I'm working on an adapter that will hopefully eliminate the light coming between camera lens and eye piece. It has frustrated me thus far to see some beautiful fossils but not able to capture them digitally.  Your description has helped me understand where I can improve.  I hope to see more of your excellent work.

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Squali,

 

Thanks very much for your kind comments -- I'm very glad to hear that some members of the forum find these posts of interest.  I'm hoping to move on to some of my numerous samples of micro material from the Cretaceous Gulfian deposits, which may also prove of value.

 

Rumi

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doushantuo

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Whoa,Ostracods!!Finally!!

GOOD photography!!

Kudos ,Rumi.Excellent piece of work!!

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Great to see these quality photos accompanied by equal quality descriptions. 

 

Its an inspiration to fossil enthusiasts that there are hidden treasures waiting to be discovered.

 

I've done some work with Paleozoic ostracods. However, not really my forte as I'm more familiar with conodonts and foraminifera.

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

 

Rumi

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Exquisite photos Rumi.  I didn't realize that Cornigella was found in the Permian as I know they are reported in the Middle Devonian of the Great Lakes.  I've been away from the Forum for awhile (my company blocking the site didn't help. :( ) but I got a email alert on your blog entries and I'm back trying to catch up on all micro-related topics!  Sorry to read about the loss of  Ectodemites. Hopefully you'll find another.

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