pleecan

Arkona Devonian Star Shaped Fossil Object 1Mm:

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Arkona Devonian sediments...... Found this interesting star shaped object size = 1mm.... What is it?

post-2446-0-90645000-1294626620_thumb.jpg

Calibrated scale= 3mm diameter

post-2446-0-10677500-1294626751_thumb.jpg

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very interesting

The only things that come to mind for me are echinoderms (because of their 5-sided radial symmetry) and foraminifera.

Subscribing here to see what thoughts come out about this one

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Gotta' be a Foram...?

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Peter,

Found this in my searching. Hope it helps.

I know the article refers to living - not fossil forams, but may be a jumping off point?

Regards,

Edited by Fossildude19

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Peter,

Found this in my searching. Hope it helps.

I know the article refers to living - not fossil forams, but may be a jumping off point?

Regards,

Forams... as Auspex and Mr. Ed. had pointed out....

thanks Tim!!! It does look like a Modern Day critter but this fossil is from the Devonian.... not much has changed and the size is about right 1-2mm range.....

another thought... could this simply be a crossection of a crinoid stem....

PL

Edited by pleecan

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There are no Dactylocrinus at Arkona. It is probably from a Decorocrinus (aka Botryocrinus).

Thanks for the insight Crinus!

PL

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I did show the pictures to museum people and got the following response:

"Anything with that kind of regular pentameral symmetry should be of echinoderm origin (as you no doubt know!), but because it's so small and there's no central lumen, a crinoid columnal identity seems unlikely. Dermal sclerites of holothurian echinoderms - the group that includes modern sea cucumbers - are about the right size, but I'm not aware of any that have such a strict stellate morphology. One thing that concerns me a little is the mineralogy of the piece ... it doesn't look calcitic, which would be the case if it comes from an echinoderm. Instead, it has a kind of siliceous appearance, so I'm not ruling out an aberrant sponge spicule as a remote possibility (sponges don't normally have pentamerous spicules)."

So mystery item remains....

PL

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Thanks Guys for the response .. could it be part of Dactylocrinus?

http://fossils.valdosta.edu/lists/frameset_pages/home_lists_echino.html

Funny.....why do they have a Trilobozoan (eurypterus) and another arthropod (Tribranchidium) on their echinoderm page?

Anyway...

This piece seems more translucent than I'm used to seeing in crinoid fossils. It's much more like some of the forams or diatoms (though it may be too big for a diatom) I've seen.

Do we have any actual crinoid examples (columnal or other) that have this translucent appearance?

Edited by Mr. Edonihce

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Funny.....why do they have a Trilobozoan (eurypterus) and an arthropod (Tribranchidium) on their echinoderm page?

Anyway...

This piece seems more translucent than I'm used to seeing in crinoid fossils. It's much more like some of the forams or diatoms (though it may be too big for a diatom) I've seen.

Do we have any actual crinoid examples (columnal or other) that have this translucent appearance?

I don't recall seeing translucent crinoid sections in my collection.... when I get home I will post what the star fossil looks like when dry compare to wet.... the image shown is taken with the star fossil submerged in a film of water to change the refractive index.... and bring out the details.... when wetted

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This is what the fossil looks like prior to wetting....

Lower bottom right is a crinoid crossection.... est. 0.75mm is size.

post-2446-0-78352400-1294703810_thumb.jpg

And now hydrated ...

post-2446-0-15283200-1294703944_thumb.jpg

Edited by pleecan

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Wow what great pics Pleecan! could you post a note with respect to the photographic details?

Your macro/micro pics are really clear. I've been following in the photography forum and appreciate your 'candidness':D

I don't suppose starfish fry looked like starfish?

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Funny.....why do they have a Trilobozoan (eurypterus) and an arthropod (Tribranchidium) on their echinoderm page?

Anyway...

This piece seems more translucent than I'm used to seeing in crinoid fossils. It's much more like some of the forams or diatoms (though it may be too big for a diatom) I've seen.

Do we have any actual crinoid examples (columnal or other) that have this translucent appearance?

Yeah, I felt quite the idiot wondering why those others were there

funny to hear you ask bout translucent crinoid, I spent 3 or 4 hours cleaning one this afternoon.'Course when I finally tried to shoot it, it was dark, and the pics are unsatisfactory.

As far as the star, I have alot of crinoids that are the perfect shape and size to have made this, but I've never seen a hint of calcification in those hollows, so I hope it's something else.:)

Edited by xonenine

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This is what the fossil looks like prior to wetting....

Lower bottom right is a crinoid crossection.... est. 0.75mm is size.

post-2446-0-78352400-1294703810_thumb.jpg

And now hydrated ...

Cool. Thanks for the two conditions.

So, not for argument, but just for clarification....do you have positive ID of that roundish item bottom-center-right being crinoid columnal, or is that conjecture based on formation and/or proximity to other organisms?

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Wow what great pics Pleecan! could you post a note with respect to the photographic details?

Your macro/micro pics are really clear. I've been following in the photography forum and appreciate your 'candidness':D

I don't suppose starfish fry looked like starfish?

Here is the camera configuration:

post-2446-0-31267900-1294708368_thumb.jpg

Camera is 3 mega pixel Nikon Coolpix 995 3x zoom

Direct coupled with a 3" custom made projection tube with RMS thread to accept std. microscope objectives

I am using high end microscope objectives in this case 10X Apochromatic Objective , infinity corrected ( worth more that the camera )

Lighting is CFL spiral bulb at 6000K

I put the scale there to show you that the objective lens is huge.

I was wondering if indeed this is a baby starfish????? but at 1mm???

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Cool. Thanks for the two conditions.

So, not for argument, but just for clarification....do you have positive ID of that roundish item bottom-center-right being crinoid columnal, or is that conjecture based on formation and/or proximity to other organisms?

The circular objects are common and I think they are crinoid stem crossections... this is Arkona Shale / rotted to clay identical to the fauna and flora of Michigan Basin.. Middle Devonian. ... this material is from the sediments that collected at the bottom of my ultrasonic cleaner unit... normally I would throw the stuff out but now saved and analysed for microfossils... lots of fun.

Edited by pleecan

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Thanks Pleecan, good luck with the starfish ;):D

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I would quess weird crinoid stem. Could it be a cast of the flower/star shaped hole inside the crinoid ring???

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I found an identical star shaped object from the following website:

http://www.eeob.iastate.edu/faculty/DrewesC/htdocs/fossil-buttons.htm

left hand side.... described as a "crinoid fragment" yet ROM disagrees

Well, actually....it's not an "identical" match (consider the texture and apparent pattern on the one in the new link). So, while I couldn't deny they're the same thing, they certainly look like they could be from totally different organisms.

Whatever it is, it could be the same thing if the one in the OP is just much more weathered, but they're not even in the same size range.....this one is 1/10th of a mm, while I think the original one in this thread is 1 mm.

Not that that would mean they can't be different sizes of the same thing.....there are indeed crinoid columnals of both sizes that are generally star shaped.

This one just seems different.....I guess the translucence still throws me off.

Are there any positively identified crinoid pieces/parts from this same formation, and if so, what are they replaced with?

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Well it still remains an interesting mystery fossil....

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Here's one that I found; however Silurian in age, that's quite similar as well. I still dont have a possitive ID on my fossil.

post-2411-0-69068700-1295117979_thumb.jpg

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^^^^^ another interesting specimen, Rob.

Hmm, I don't know. With all three of these specimens so far, the only thing in common between them is the fact that they are all star shaped.

Of course, any good 'fossil shape identifier' guide would suggest that, if it's a star shape (especially if it's got 5-sided radial symmetry), it's probably an echinoderm.

This one actually has a shape that looks quite star-fish-like, but I have no idea what their 'young' are like, etc.

To be clear, I'm still not saying that these things are for sure not crinoid pieces. I just don't think we can say for sure yet with the info available thus far.

Edited by Mr. Edonihce

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