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Tiesta

Diverse Trace And Corpolite Fossils Of The Twin Cities

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Tiesta

Hopefully this picture works. I found this one a few weeks ago in lilydale - seem to be soft Decorah limestone. For a bit while I thought it was a unusual feeding tracks type but the patterns seem to be too regular - I can't see any exoskeletions on this one that would be typical of crinoids but my research hadn't come up with anything else for it. Nothing in books and internet about echinodermata that looks like this one. The only way to describe it is all the branches come from the central stem section and that it once had some kind of organic skeleton that held together long enough for fine sediments to get in before rotted away completely leaving behind a mold.

post-2767-0-00023600-1435425342_thumb.jpg

Edited by Tiesta

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FossilDAWG

Sorry, but I am pretty sure it is a trace fossil, not a crinoid. There is no evidence of any plates or ossicles, and although you say the "patterns seem too regular" I don't see that. If it were an impression or mold of a crinoid we would still be able to see the arms bifurcating in a consistent manner, i.e. all the arms dividing at the same distance from the "calyx". In this case there is no calyx, just "arms" bundled together, and the "arms" divide (or not) at irregular intervals.

Don

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howard_l

Crinoids seem to be some of the most resistant fossils to solutioning they are pretty much pure calcite while living not Aragonite like a lot of marine fossils during life. I would think even if it was solutioned out the mold and cast would have shown more detail. I vote trace fossil also.

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piranha

This one appears to be Phycodes isp. OrdovicianAtlas.org has a couple of good examples that match well with the posted image: LINK

 

IMG1.jpg

 

figure from:

 

Miller, W., (2007)

Trace Fossils: Concepts, Problems, Prospects.

Elsevier Scientific Publishing, 611 pp.

 

 

 

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Tiesta

Thanks piranha. Now I will have to rename this section trace fossils since I have plenty of other trace fossils. Beside fossildawg I am still learning. I know of modern day limpets making branch paths as they feed on algae on rocks then return back to the same spot but a tree style feeding path in the muck by a unknown animal? That's new for me.

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