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SteveE

Silurian - crinoid vertebra?

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SteveE

Central PA,  Mifflintown-Bloomsburg (undividied)    Block collected from roadsite float.  Its pretty variable, with a flaky/fissile layers alternating with slightly more cohesive ones.  Lots of broken brachiopod bits.   For an experiment to I dropped an unremarkable flake the size of a large coin in some vinegar and let it soak for a day.  The flake had a couple brachiopod bits and I wanted to see if they would fall free or dissolve in place.   The brachiopds disappeared and I was left with this (see pics).    Of course I got really excited and thought I had an early fish spine, but now I think I dissolved a crinoid stem and what we see is the matrix that filled in the soft bits.  What do you think?  Total length is 3/4"

IMG_0850.JPG

IMG_0871.JPG

IMG_0874.JPG

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abyssunder

Although the pictures are a bit blurry, it looks like there were crinoid pluricolumnals, now almost totally dissolved, leaving behind external molds of columnals and internal molds of lumens with the crystallized sediment infill between what once were columnals.

 

eroded-crinoid-stem-from-lake-cumberland-kentucky-mississippian-period-fort-payne-formation-4.jpg.6dc66ccc9f3d58389a2c8f61645d9485.jpg

picture from here

 

crinoid-internal-mold-lumen-copy.jpg.f871188330c35f938f0d7349a91bfab2.jpg

picture from here

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SteveE
5 hours ago, Rockwood said:

Yes that is a lumen cast from a crinoid stem inside the mold of it.

Edit: Vertebra does not apply.

Thanks Rockwood, that's what I thought.   Searching google images on _Crinoid vertebra_ led to a web page that has a diagram of various cross sections labeled "vertebra".  I thought that must be trade jargon.   It's really fun realizing the flake showed no sign of this stem, but a day in Vinegar and...... voila!   Makes me wonder what else is (was) in all the rocks I "threw back".

Edited by SteveE

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SteveE
1 minute ago, abyssunder said:

Although the pictures are a bit blurry,

 

Heh.... that's shooting with a handheld IPod through a handlens for you!  Nice pics  MOTM... that's some careful prepping

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abyssunder
6 minutes ago, SteveE said:

Nice pics  MOTM...

abyssunder is my username..., MOTM means "Member of The Month", a very nice appreciation from TFF. :)

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Rockwood
2 hours ago, SteveE said:

Thanks Rockwood, that's what I thought.   Searching google images on _Crinoid vertebra_ led to a web page that has a diagram of various cross sections labeled "vertebra".  I thought that must be trade jargon.   It's really fun realizing the flake showed no sign of this stem, but a day in Vinegar and...... voila!   Makes me wonder what else is (was) in all the rocks I "threw back".

It was once thought that crinoid columnals were homologous to vertebra. The idea has since been dismissed though. 

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Zenmaster6
4 hours ago, abyssunder said:

abyssunder is my username..., MOTM means "Member of The Month", a very nice appreciation from TFF. :)

:hearty-laugh:

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SteveE

well I always like making others laugh or smile..... note to self, user names on my screen are nearly invisible (white on light grey) until AFTER I log in....  Hmmm next time I'm at a roadcut, I'll have to try logging in, and then maybe I'll see more fossils....

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