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BobWill

Odd protruberance on Pennsylvanian Sponge(?)

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BobWill

I found this twiggy fossil at the Lost Creek Dam site in Jacksboro Texas. It's the Finis Shale Member of the Graham Formation, Upper Pennsylvanian. I thought it might be a Fissispongia jacksboroensis but now I'm wondering if that is right. The two branch-like protuberances  have some wavy striations on them I haven't seen before. Any ideas?

5c6f00046837f_twiggys001.jpg.6f5c9ebfc90ebb54f13bc257b9affd52.jpg

 

5c6f00582545f_twiggys007.jpg.2c94bb0a000ffc69ad1e9dfc4a98c00a.jpg

 

5c6f001c01b5f_twiggys003.jpg.e0762c6ade0ebe48ef0a563acd63f00f.jpg

 

5c6f00300e39b_twiggys005.jpg.95c3f555dbb98aea8b8a08e3bc8efe4f.jpg

 

5c6f0040c94a8_twiggys006.jpg.748bbd8ca3a4edd07148276e8a15cadd.jpg

 

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fifbrindacier

Other sponges ?

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BobWill

Polishing the end did not expose anything useful but I realized that there are two and a possible third branch, all in a row.  Looking through Index Fossils of North America at some bryozoans with fenestrate architecture I found  an older species, Fenestrellina stellata, described as having "pecular channeling of branches and dissepiments [cross bars]" so I think Dr. Neuman may be on the right track.

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Archie

Sorry cant help with ID but it's very beautiful whatever it is! 

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Al Dente

Gorgonians have very similar holdfasts.

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BobWill
1 hour ago, Al Dente said:

Gorgonians have very similar holdfasts.

Great! I'll just label it "Coral, Sponge or Bryozoan" and let the observer choose :)

 

I'm afraid I know very little about all of them so my question may not make sense but can a coral have two holdfasts beside each other like this, or do you think the branches with the wavy grooves are where two corals attached to whatever this stick is?

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Al Dente
49 minutes ago, BobWill said:

'm afraid I know very little about all of them so my question may not make sense but can a coral have two holdfasts beside each other like this, or do you think the branches with the wavy grooves are where two corals attached to whatever this stick is?

I think it can be more than one individual or a single one that branched. This thread has nice photos of modern soft corals with grooved bases.http://www.thefossilforum.com/index.php?/topic/81182-what-is-this/

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abyssunder

My first thought, seeing those special details, was holdfast. I agree that the gorgonian coral holdfast(s) might be a possibility, but what is bothering me, is that I don't know if they were present in the Carboniferous. :headscratch:

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abyssunder
5 hours ago, BobWill said:

Polishing the end did not expose anything useful but I realized that there are two and a possible third branch, all in a row.

Can we have some images of the polished ends, Bob?

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BobWill
37 minutes ago, abyssunder said:

Can we have some images of the polished ends, Bob?

I'm afraid this is all I could manage to expose with some 400 grit sandpaper. I don't know what else I should use.

 

WIN_20190222_18_56_02_Pro.jpg.5251340b160f5e36cf01c1c25eda187a.jpg

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daves64

600 & 1000 grit wet/dry sandpaper may expose more, simply by smoothing the scratches away. I hand sand rocks & amber & generally end up going as high as a 14,000 grit equivalent bonded sanding sheet, but 600 followed by 1000 should do the trick for "cleaning a window" so to speak.

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abyssunder
18 hours ago, BobWill said:

I'm afraid this is all I could manage to expose with some 400 grit sandpaper. I don't know what else I should use.

Thank you for the picture, Bob. I'm late as always. Eric has posted what I want to post yesterday.
The reason why I asked for the polished transverse section was to see the concentric "rings", but I'm not sure I can see them in your specimen.

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