Segmented Cambrian fossil

[jj_MT]

Hi there!

 

I picked up this fossil while trilobite hunting over the summer along the continental divide in Montana. I keep looking at it and my curiosity is getting the better of me. I don't know if it is a trace fossil or a plant or something else. All I know is its not a trilobite. Maybe related to a stalked echinoderm or a crinoid, unfortunately I haven't found any applicable literature.

 

This was found loose among various trilobite fragments at the base of Dearborn Limestone cliffs with Pagoda Limestone, Pentagon Shale and Steamboat Limestone above so this should be Middle Cambrian.

 

The intriguing aspect to this fossil is the seemingly segmented appendages stemming from a central stalk. I am just another novice collector who enjoys all aspects of the natural world with limited geology experience but I more fossil hunts planned.

 

 

Thanks for looking,

 

jj

[ynot]

Welcome to TFF!

I think they are burrow cast (trace fossils).

[jj_MT]

Interesting, thank you!

 

Any ideas on what critters would have made them?

[ynot]

Not until one shows up in the burrow.

[jj_MT]

Haha sounds good, I'll keep chipping away...

 

 

Same locality. More burrows or trails? Much larger in size, probably close to 1cm wide "trails"

 

This was too big to pack out so it's still out there.

[ynot]

4 minutes ago, jj_MT said:

More burrows or trails?

Yes.

[jj_MT]

Very cool, much appreciated!

[westcoast]

1 hour ago, ynot said:

Welcome to TFF!

I think they are burrow cast (trace fossils).

Overall they do look like burrows however i am drawn to the 'segmented' appearance. Are they post depositional micro joints or part of original? 

[ynot]

4 minutes ago, westcoast said:

Overall they do look like burrows however i am drawn to the 'segmented' appearance. Are they post depositional micro joints or part of original? 

I think they are an artifact of the animal that made the burrow.

The length of the segments are inconsistent and the "branching" looks more like coincidental contacts.

[abyssunder]

The bifurcating, segmented, running in all directions character of the appendages of the  first specimen reminds me of rhizoids, so I think they might be from the anchoring system of echinoderms.

 

[ynot]

7 minutes ago, abyssunder said:

  first specimen reminds me of rhizoids, so I think they might be from the anchoring system of echinoderms.

Shouldn't the segmentation of an echinoid be consistent in length, and the branching should be more frequent.

 

I do not see echnoid in the piece.

[abyssunder]

The segmentation could be irregular or missing. High-res images are needed for a better ID.

 

[jj_MT]

Some additional pictures, hope these help clarify. These are as high-res as I can get.

 

 

edit: I am trying to upload two closer pictures, but the upload is failing. I will try again shortly. The wider "structure" is flat while the narrow one is more rounded.

 

Edited February 25, 2018 by jj_MT

[westcoast]

Are you sure these are middle Cambrian?

 

[jj_MT]

@westcoast I've read nothing to suggest anything other than middle Cambrian. Highly unlikely someone would have planted anything at this locality.

 

Here is an excerpt (apologies to the following citation) from "Correlation of the Cambrian Formations of North America" by the Cambrian Subcommittee. Bulletin of the Geological Society of America, Vol. 55, PP. 993-1004, 1 PL. 1944.

 

[piranha]

Do you have this one?

 

Deiss, C. (1939)

Cambrian stratigraphy and trilobites of northwestern Montana.

Geological Society of America Special Papers, 18:1-135

 

 

Here is another excellent correlation chart for the Middle Cambrian of Montana:

 

Theodosis, S.D. (1955)
Cambrian System in northwestern Montana. 

In: Guidebook: Sixth Annual Field Conference.

September 7-9, 1955, Billings Geological Society 

 

[abyssunder]

2 hours ago, jj_MT said:

The wider "structure" is flat while the narrow one is more rounded.

Plants didn't exist at that time and the specimen is not enough flat to be alga / seaweed, in my opinion, although it has some characters of them (somehow reminding of Jania), considering the character of the later myelodactilid cirrals I would remain in the realm of my original thought.

 

[jj_MT]

@abyssunder Thanks for the additional info and great images! Do you have any resources for Cambrian rhizoids?

 

I'll continue to try uploading additional pictures.

 

@piranha I have the 1939 Deiss paper, it's basically what I followed to find the locality. Excellent resource!

 

I am not familiar with the 1955 Theodosis, I will have to check it out, thank you!

[doushantuo]

possibly eocrinoid holdfast?

[abyssunder]

24 minutes ago, jj_MT said:

Do you have any resources for Cambrian rhizoids?

No, i haven't.

 

10 minutes ago, doushantuo said:

possibly eocrinoid holdfast?

That was my initial thought.

[jj_MT]

@abyssunder  Anything specifically I might be able to look for to either confirm or rule out an eocrinoid holdfast? 

[doushantuo]

edited by member

[MeargleSchmeargl]

As far as what left it, I'm no expert, but that is quite a neat trace fossil! 

[jj_MT]

@MeargleSchmeargl thanks! The irregular segments really caught my eye as something different. 

[EMP]

20 hours ago, jj_MT said:

Hi there!

 

I picked up this fossil while trilobite hunting over the summer along the continental divide in Montana. I keep looking at it and my curiosity is getting the better of me. I don't know if it is a trace fossil or a plant or something else. All I know is its not a trilobite. Maybe related to a stalked echinoderm or a crinoid, unfortunately I haven't found any applicable literature.

 

This was found loose among various trilobite fragments at the base of Dearborn Limestone cliffs with Pagoda Limestone, Pentagon Shale and Steamboat Limestone above so this should be Middle Cambrian.

 

The intriguing aspect to this fossil is the seemingly segmented appendages stemming from a central stalk. I am just another novice collector who enjoys all aspects of the natural world with limited geology experience but I more fossil hunts planned.

 

 

Thanks for looking,

 

jj

 

I think the lined burrows could be neonereites:

 

 

19 hours ago, jj_MT said:

Haha sounds good, I'll keep chipping away...

 

 

Same locality. More burrows or trails? Much larger in size, probably close to 1cm wide "trails"

 

This was too big to pack out so it's still out there.

 

These are a little harder. They're not Skolithos, maybe some kind of planolites?