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Rocky Stoner

Crinoid ? Holdfast ?

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Rocky Stoner

The symmetry in this little feature really is amazing to me.

Its about 8mm dia.

I'll go out on the limb and guess that it is the mold of a small crinoid holdfast.

(its a very slender, shaky limb though)

Do you recognize it ?

 

Thanks again :)

IMG_0009.JPG

IMG_0007.JPG

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FossilDAWG

How unusual!  I don't think it is a holdfast, as 1) it is very symmetrical and crinoid holdfasts are not, and  2) it does not seem to have a central attachment point for a stem.  However, what it is I don't know.  Very intriguing!

 

Don

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ynot

The hold fasts of crinoids that I an familiar with look like segmented tree roots.

If it is a holdfast I do not believe it is crinoid. But I have no idea what it could be.

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Rocky Stoner

Camera battery went dead. Soon as it charges up I'll get better lighting and provide better pics showing the depths of the holes better.

(ok, I barely skittered back off of that limb just as it was breaking ^_^)

... standing by ......

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DPS Ammonite

My best guess is a placoderm (armored fish) scale. See: https://www.researchgate.net/figure/241075604_fig3_Fig-3-Placoderm-material-from-the-Lochkovian-of-Spain-A-I-Kujdanowiaspis-podolica "First Perigondwanan record of actinolepids (Vertebrata: Placodermi: Arthrodira)from the Lochkovian (Early Devonian) of Spain and itspalaeobiogeographic significance" by Vincent Dupret et al.

 

Note similar bumpy plate with bilateral symetry: figure K.

Placoderm.JPG

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WhodamanHD

Something about it feels crinoid, I don't know what. If it is placoderm, you have found the holy grail! These things are rare in any formation, and I haven't heard of any in the mahantango.

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Rocky Stoner

I do not think the fish plate would fit.

The cystoid plate is a similar pattern of bumps and ridges ... but not quite the same.

The cast of this would have ridges with spikes on them plus some individual spikes.

Tried several photos with the flash and other variations, this is the best I can get.

Keep in mind, it is only about 8mm across.

Thanks

IMG_0016.JPG

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WhodamanHD

I'd agree with cystoid, there are different species with different features. 

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Rocky Stoner

.... one more pic.

7 minutes ago, WhodamanHD said:

I'd agree with cystoid, there are different species with different features. 

The cyctoid plates are apparently all polygonal, the outer edge of this is a curve, not straight lines like a polygon. (clearly seen under the scope)

This is also an irregular pattern, although symmetrical where the cyctoids are a more regular pattern.

I searched many, many illustrations and pictures and found none that resemble this. Have you any pictorial examples ?

I'd really like to see something similar.

Thanks

IMG_0027.JPG

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Arizona Chris

Thats a strange one!  The outside seems to have a crude five fold symmetry suggesting an echinoderm of some sort.  Maybe a crinoid or cystoid calyx?

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Rocky Stoner

Thanks for your input Chris.

Nothing really definitive on this one yet, will keep this item open and un-tagged for now. :fingerscrossed:

Have yet to see any other references that are convincingly similar.:popcorn:

Maybe should call Georgio .... or MUFON :)

 

Thanks again.

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WhodamanHD

This is my guess as to why it is not as straight as would be expected from a cystoid, cystoid plates are curved upward (kinda like a contact lense) and when you split the shale, the top layer came off with it. You can still see the vague outline of the pentagon. I think caryocrinites is found in the mahantango by the way.

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Rocky Stoner
15 hours ago, DPS Ammonite said:

Another possibility is a cystoid plate.

 

14 hours ago, WhodamanHD said:

I'd agree with cystoid, there are different species with different features. 

I'll go with this as well.

I can find nothing else that comes this close.

Thanks Gents,

:)

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abyssunder

I think it could be a blastoid calyx imprint in the matrix,  the circled portion being the imprint of one ambulacral zone.

 

c.thumb.jpg.c9953317538de7b001cd7e553ae949df.jpgb947c1b032f127af25d72c8071fd2a9a--nephilim-gem-stones.jpg.b5d14933a38d30c25f607aff473ac66f.jpg

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Rocky Stoner

Very interesting possibility, thanks for posting !

I tried to prep that little piece off in the center of your circle to maybe see more of the feature but it is part of the matrix.

Try as I may, I cannot get a good pic that shows the depth and shape of the holes.

They are tapered and have a radiussed point at the end.

I'm considering making a cast but would then have to destroy the mold to extract it.

If there was a way to seal the surface, then use a mold release agent before filling it with latex, or silicone I might be able to salvage the mold. Any suggestions ?

Or use some glass reinforced epoxy (or polyester) and destroy the mold as the holes are splayed a bit and would not allow a rigid cast to be extracted. Suggestions ?

 

Thanks to all for your participation and thoughts :)

IMG_0028.JPG

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