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Crinoid, Cephalopd, Or Something Else?


Indian_money

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I have created a pretty large collection out of crinoid stems from creeks here in Tennessee, but after looking through many fossil fragment photos online I have suddenly become unsure of a couple of pieces in my collection.

Are they crinoid fragments as I originally assumed, or are they cephalopods or maybe something else? And hey, maybe they are just crinoid stems but I will always wonder if I don't ask.

I appreciate all of your help :) :)


EDIT: I added a photo of the backside of the last fossil

post-16024-0-76190000-1406832191_thumb.jpg

post-16024-0-63518700-1406832201_thumb.jpg

post-16024-0-44351100-1406832241_thumb.jpg

post-16024-0-94626400-1406838586_thumb.jpg

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They are cephalopods. In the middle photograph you can see a remnant of the siphuncle, a tube that ran the length of the shell, penetrating through all the camerae (chambers). Also the septa (the part of the shell that divides the camerae) are highly curved, and the camerae are hollow. In contrast, if this specimen (and the others) were crinoid stems the discs of the stem would be solid, and the juncture between the discs would be flat not curved or bowl-shaped.

The specimens are a bit too worn to identify the genus, much less the species, with much confidence. An accurate ID would require a clear view of the structure of the siphuncle.

Don

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They are cephalopods. In the middle photograph you can see a remnant of the siphuncle, a tube that ran the length of the shell, penetrating through all the camerae (chambers). Also the septa (the part of the shell that divides the camerae) are highly curved, and the camerae are hollow. In contrast, if this specimen (and the others) were crinoid stems the discs of the stem would be solid, and the juncture between the discs would be flat not curved or bowl-shaped.

The specimens are a bit too worn to identify the genus, much less the species, with much confidence. An accurate ID would require a clear view of the structure of the siphuncle.

Don

Sorry I'm a cephalopod novice :blink:

These fossils are from inside the shell? Meaning they are the filled up cavities of the inner shell?

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The third one looks like it could have been a pretty large crinoid stem piece. Any pictures from the end?

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The third one looks like it could have been a pretty large crinoid stem piece. Any pictures from the end?

Actually Ryan, after searching this site I have found my own answer on the last fossil!

check out this previous post, and someone has a picture of pretty much the same thing I found, and a seriously knowledgeable guy named @BobWill explains the species perfectly.

http://www.thefossilforum.com/index.php?/topic/39056-cephalopod-question/

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