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Rockhopper

Marine invertebrate, Permian (?), Death Valley

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Rockhopper

I found this fossil associated with crinoid fragments, a fish spine, and corals. The location was a small canyon in the Cottonwood Mountains of Death Valley. Collecting is not allowed, so unfortunately I have only the one field photograph. Any ideas? It's small; length is about 1.5 cm, a little over half an inch.

 

 

Unknown1a.jpg

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Foozil

Maybe a bryozoan or coral encrusted crinoid stem.

Also do you have any pics of the fish spine?

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Tidgy's Dad

Looks like a fossil chiton to me. 

It's very beautiful! :)

Oh, and hello, and a very warm welcome to TFF from Morocco! 

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abyssunder

Chitons have eight segments.

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Rockhopper

I was wondering if the grayish projections were secondary growths. Here's a picture of the fish spine. (edit: it's about 6 cm long, about 3 inches. Not a fish you'd keep for dinner, exactly.)

 

FishBackbone.jpg

Edited by Rockhopper

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Tidgy's Dad
33 minutes ago, abyssunder said:

Chitons have eight segments.

True.

Okay a related early polyplacophoran? 

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GeschWhat

Beautiful! :popcorn:

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DevonianDigger

Whatever it is, it's quite cool! At least you'll always have the picture.

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ynot
2 hours ago, Tidgy's Dad said:

True.

Okay a related early polyplacophoran? 

Have to disagree with this.

We are looking at a transverse cross section with an internal structure exposed.

There is a smaller one that is a better cross section just below the main piece.

I agree with an encrusting bryozoan on something (crinoid or cephalopod?).

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TqB
7 hours ago, Foozil said:

Maybe a bryozoan or coral encrusted crinoid stem.

Also do you have any pics of the fish spine?

 

I agree, bryozoan on crinoid.

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Rockhopper

Nice ID, thanks all. And thanks for the welcome to the forum!

 

-- Don

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Coco

Not a chiton. Have a  look on my signature, you can find some publications about recent polyplacophora. As Abyssunder said : chitons always have 8 plates.

 

Coco

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Rockhopper

I'm slightly embarrassed, as the segmented section in the original post pretty much exactly matches the crinoid segments found in other rocks at the site -- clearly a fragment of crinoid stem. I should have figured that out from the context. The grayish halo of other material may be badly weathered: wherever the other fossils included similar grayish mineral, the mineral appears to have weathered much faster than the rusty-brown matrix. Perhaps it's a carbonate, and particularly soluble. Given the degree of probable erosion, I wouldn't know a bryozoan from an encrusting coral. Or from bubblegum. In the image below, from the same site, you can see crinoid segments which have eroded preferentially, leaving in one case something that looks very much like vertebrae -- but which is really the cast of the inner canal of the criniod stem, I think, surrounded by the eroded mineral of the stem discs. To the right are a couple of stem segments that have mostly lost the gray mineral, leaving the inner canal surrounded by the radially-grooved inter-segment surfaces. At least, that's how I interpret it. Tricky stuff, these fossil tricks.

 

image.thumb.png.eaa15365d23a4c6fbd01dd76f3d72367.png

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