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Rocky Stoner

Another crinoid calyx

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Rocky Stoner

Good day folks,

  I found another crinoid calyx similar to the ones found earlier but with a little bit more definition. I exposed this one with a split, the others were on the exposed surface of a piece of shale that was loose in the plowed up rubble. I was hoping to find more of these, this one was just a few feet from where I found the other two. The gastropod was a bonus.

And of course, two more trilobite pygidia along with this small cephalon ... # 29.

 

 

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Foozil

Awesome! :wub:

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Fossildude19

Very cool, Rocky. :) 

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minnbuckeye

Mother nature has provided you with very eye appealing hash plates!!! Very "artistic" . Love to see your finds.

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JohnBrewer

Nice!

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WhodamanHD

That's a purty snail! Nice calyx and trilo-bit as well!

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Jeffrey P

That's an awesome find. Congratulations and thanks for sharing. 

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crinus

That is not a crinoid.  It is a Hexagonaria coral.

Joe

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Rocky Stoner
10 minutes ago, crinus said:

That is not a crinoid.  It is a Hexagonaria coral.

Joe

Hi Joe, thanks for chiming in !

Here is another one I found about a month ago in the same area.

Does this also resemble the Hexagonaria coral ?

Thanks again.

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Fossildude19

They do look quite a bit like Pleurodictyum corals. - Honestly  that was my first thought on the first picture. But the presence of the single crinoid type columnal - (the first one posted here has what appears to be a 5 sided star shaped nub, the second has a pentagonal shaped nub.) in the center of the fossil  has me scratching my head. Could be a coincidence, I guess. :headscratch:

 

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piranha

These specimens match well with the Mahantango crinoid: Arthroacantha sp.

 

figure from:

 

Burns, J. (1991)
Fossil collecting in the Mid-Atlantic states with localities, collecting tips, and illustrations of more than 450 fossil specimens. 
The Johns Hopkins University Press, 216 pp.

 

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Rocky Stoner
44 minutes ago, Fossildude19 said:

They do look quite a bit like Pleurodictyum corals.

Just picked these up today.

I have these labeled Pleurodictyum americanum from previous ID posts.

Similar ?

Thanks.

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WhodamanHD

Was about to say, the connection point is on top so it's must be a crinoid...

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ynot
51 minutes ago, Fossildude19 said:

- (the first one posted here has what appears to be a 5 sided star shaped nub, the second has a pentagonal shaped nub.) in the center of the fossil  has me scratching my head. Could be a coincidence, I guess. 

In the first piece the 5 sided columinal does not match the 6 sided plates and there are no smaller joining plates. coral seems a good id.

In the second one the columnal matches the surrounding pattern (both are 5 sided) and there are smaller joining plates around the columinal joint.  Calyx sounds good for this one.

 

 

Edit- In @piranha's diagram the columnal is round and the first plate is pentagonal, where as the op's pieces are different.

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Rocky Stoner
3 minutes ago, piranha said:

These specimens match well with the Mahantango crinoid: Arthroacantha sp.

 

figure from:

 

Burns, J. (1991)
Fossil collecting in the Mid-Atlantic states with localities, collecting tips, and illustrations of more than 450 fossil specimens. 
The Johns Hopkins University Press, 216 pp.

 

IMG.thumb.jpg.c0a3a2ab3091aebfcce7598766b6e547.jpg

I don't think one can get any closer than that for verification !

Thank you piranha !

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piranha
43 minutes ago, ynot said:

Edit- In @piranha's diagram the columnal is round and the first plate is pentagonal, where as the op's pieces are different.

 

 

There is variability in different specimens.  Here is another Arthroacantha sp. with all hexagonal plates.

 

IMG.jpg.19da82ed0a9eb2d3b1fcae769f32289a.jpg

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ynot
1 minute ago, piranha said:

There is variability in different specimens.

OH Duh! (emoji hits forehead).

 

 

@Pagurus Hey Mike - can You do a forehead slapping emoji? (I seem to need one quite often.)

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Rocky Stoner

This is a polygon shape with star like patterns throughout.

Hard to get a pic just right but hope you can make it out ok.

Could this be related ?

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WhodamanHD
24 minutes ago, Rocky Stoner said:

This is a polygon shape with star like patterns throughout.

Hard to get a pic just right but hope you can make it out ok.

Could this be related ?

It's an bryozoan of some sort.

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FossilDAWG

I agree that the specimen in question is an internal mold of a crinoid calyx.  One thing that confuses me is that there appear to be 6 basal plates (assuming the central one with the attachment point is an infrabasal).  The illustration shows 5 basals, but the photo of another specimen shows 6 basals.  5 would be expected for crinoids in general (pentameral symmetry).  However a few crinoids, such as Hexacrinus, have an unusual 6-fold symmetry.  Does Arthrocantha sometimes have an extra basal?

 

Don

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piranha
1 hour ago, FossilDAWG said:

I agree that the specimen in question is an internal mold of a crinoid calyx.  One thing that confuses me is that there appear to be 6 basal plates (assuming the central one with the attachment point is an infrabasal).  The illustration shows 5 basals, but the photo of another specimen shows 6 basals.  5 would be expected for crinoids in general (pentameral symmetry).  However a few crinoids, such as Hexacrinus, have an unusual 6-fold symmetry.  Does Arthrocantha sometimes have an extra basal?

 

 

Probably not.  The photo showing 6 is from a google image search for Arthroacantha.  

After visiting the photo source, it's only listed as an unidentified Windom Shale calyx.

 

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crinus

The second specimen is a crinoid.  Which crinoid, I have no idea.  The first specimen still looks like a coral.  I just used Hexagonaria because that is what I am familiar with.  Not really a coral collector.

Joe

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Arizona Chris

Fantastic images, Id like to find a site like this!  That cephalon with the eye sticking out is absolutely outrageous. ;)

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Rocky Stoner

Thanks Chris :)

Picked these up at lunchtime today.

I'd almost rather find cephalons in good condition rather than complete trilobites buggered up.

This little guy is # 33.

I'm still amazed by those eyes. The mold of the underside of the moult is more impressive that the mold of the outer surface, especially regarding the eyes. Pretty eyes !

 

Kind regards.

 

 

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ynot

Ya really got some nice hash plates coming out of Your yard there!

Thanks for sharing.

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