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GeschWhat

While scanning some of the fossil plates I found hunting with @Bev and @minnbuckeye, I noticed this little star-shaped discoloration on one of the brachiopods. Anyone have any idea what could have produced this mark? 

Maquoketa-Brac-Star2.jpg

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minnbuckeye

Very interesting. Was that on the large brachiopod?

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ynot

2 thoughts.

An attachment scar (not crinoid) or a mineral stain from a piece that was resting against it.

 

I like the latter idea better.

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GeschWhat
2 minutes ago, minnbuckeye said:

Very interesting. Was that on the large brachiopod?

Just one of the average size ones. I can post a photo if it helps.

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minnbuckeye

Would love to get a perspective on the brach in case this is truly something. Sure looks like something!

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Dretsend
20 minutes ago, GeschWhat said:

While scanning some of the fossil plates I found hunting with @Bev and @minnbuckeye, I noticed this little star-shaped discoloration on one of the brachiopods. Anyone have any idea what could have produced this mark? 

Maquoketa-Brac-Star2.jpg

Definitely looks like an asterina starfish, but being all soft tissue, it would be very weird it left any mark? And never seen one that small...

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GeschWhat

It is from one of the larger plates up where we were finding the sponge spicules. What was the name of that cliff?

Maquoketa-Brac-Star3.jpg

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GeschWhat
5 minutes ago, Dretsend said:

Definitely looks like an asterina starfish, but being all soft tissue, it would be very weird it left any mark? And never seen one that small...

I guess it's possible that it could be a stain left by something with soft tissue, but it's weird that it is just an outline. 

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GeschWhat
6 minutes ago, piranha said:

It is the remnant of a crinoid holdfast showing stellate attachment.  Very unusual and interesting association piece! :fistbump:

 

IMG1.png.1fc118ecf285bc63130f85a606df0d76.png

Thank you! I was kind of wondering if crinoids could have attachment points like that. The only thing is, I don't recall finding any crinoids in that layer/area. @Minnbuckeye is much more familiar with the location. Did you find any, Mike?

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Auspex

Can you help me understand how that would leave a 'hollow' star tracing like this?

~~.jpg

Seems that, assuming the star-shaped hole goes all the way through the holdfast, the image would more likely be a solid star, within an amorphous field (being the footprint of the holdfast).

 

I was actually wondering whether it could have transferred from contact with wrapping material.

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ynot

The problem I have with a crinoid hold fast is the lack of evidence of arms beyond the star.

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piranha
30 minutes ago, Auspex said:

Can you help me understand how that would leave a 'hollow' star tracing like this?

~~.jpg

Seems that, assuming the star-shaped hole goes all the way through the holdfast, the image would more likely be a solid star, within an amorphous field (being the footprint of the holdfast). I was actually wondering whether it could have transferred from contact with wrapping material.

 

It is not a perfect tracing.  Look again closely, there is varying thickness to the 'outline'.  The lack of a filled void is probably a diagenetic artifact.

 

 

28 minutes ago, ynot said:

The problem I have with a crinoid hold fast is the lack of evidence of arms beyond the star.

 

I think your argument is flawed, unfortunately we can't always special order fully intact Ordovician fossils.  A better explanation is: the arms are absent.

We do have a great clue in this case and it appears to be fairly obvious.  Btw, I'm all ears if there is another more obvious explanation for this fossil:popcorn:

 

 

These holdfasts types are described with pentaradial symmetry that extends into the multiplated holdfast:
"Pentapartite stems with stellate axial canals are virtually restricted to crinoids, so it is reasonable to eliminate the noncrinoid taxa from consideration."

 

Lewis, R.D. 1982

Holdfasts. pp. 57-67

In: Sprinkle, J. (ed.)

Echinoderm Faunas from the Bromide Formation (Middle Ordovician) of Oklahoma.

University of Kansas Paleontological Contributions, Monograph 1:1-369   PDF LINK

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GeschWhat
26 minutes ago, Auspex said:

I was actually wondering whether it could have transferred from contact with wrapping material.

It wasn't wrapped. There was nothing that it could have transferred from (other than another rock). You can see a little of the iron oxide on it from one of the rocks with sponge spicules.

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Auspex

I really don't doubt that Scott has the right of it, I'm just working on understanding the mechanics.

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minnbuckeye

I plotted the points of the star on a piece of paper then connected the dots. It measures out to be a perfect star!!! The problem is the marker bled through the paper and left 5 big dots on my computer screen. Is there a forum to ask how to remove this stupid mistake from my screen???

 

I do not find many crinoids in this matrix, but not saying there isn't an occasional one. 

 

@GeschWhat, did you see the star with your naked eye or were you playing with that microscope again? It is pretty small on a tiny brachiopod.

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GeschWhat

I just went up and took another gander at it under the microscope and brushed it with a soft brush. It isn't mineral staining. The star appears to be somewhat translucent. Most of the shell material appears to be missing, so perhaps a pentacrinoid holdfast??? 

2 minutes ago, minnbuckeye said:

 

@GeschWhat, did you see the star with your naked eye or were you playing with that microscope again? It is pretty small on a tiny brachiopod.

Playing with the microscope of course! I like to scan everything for microfossils. :D

 

Is this something someone is interested in or should I donate it? Mike, of course, would get first dibs.

Maquoketa-Brac-Star4.jpg

Maquoketa-Brac-Star5.jpg

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Auspex
6 minutes ago, minnbuckeye said:

how to remove this stupid mistake from my screen?

A label remover called ZO-EZE (1,1,1 trichlorethylene and isopropanol) will take it right off, without damaging your screen.

(Don't ask me how I know this....):blush:

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abyssunder

If, the star-shaped pattern represent a crinoid columnal or scar in transverse section, I'm wondering where is the lumen from the center, or if it's the lumen / cirrus scar of a crinoid, where is the crenulae or the outer mark of the columnal / cirrus? - I would eliminate a central columnal or a scar considering the patterns outside of it.
If, what it looks to be in the center is the mouth and the sticking-out crescent is the anus, I could go with crinoid crown, according to this photo, but again, the outside pattern is strange for me. There could be arms with pinnules in my thinking. Maybe there are superposed tiny layers in the sediment, making more difficult the ID?

 

fig025.jpg.eb67ec9c7177c1cbf120db070e9c3ca5.jpg

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minnbuckeye
1 hour ago, Auspex said:

Don't ask me how I know this....):blush:

@Auspex, your response has to be followed by a question, HOW DID YOU KNOW THIS! Hopefully the story will lessen how foolish I feel!

 

@GeschWhat, if you are going to discard it, Yes I would take it. But you have more contacts than I for proper ID. Though the responses have me pretty well convinced.

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GeschWhat
3 minutes ago, minnbuckeye said:

@GeschWhat, if you are going to discard it, Yes I would take it. But you have more contacts than I for proper ID. Though the responses have me pretty well convinced.

If it is something unusual, I think a brach person should have it. I just brought the brachs and slabs home to give to kids (after I scanned them for hidden treasures under the microscope). If I don't limit myself to ichnos, I'd have to get a second home to store my husband fossils. :D

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minnbuckeye
27 minutes ago, GeschWhat said:

If it is something unusual, I think a brach person should have it.

 

@Peat Burnsis a relatively close brachiopod person. I know he likes epibionts. We will see if he has seen this yet.

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Herb

tattooed brachiopod

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Peat Burns
2 hours ago, minnbuckeye said:

 

@Peat Burnsis a relatively close brachiopod person. I know he likes epibionts. We will see if he has seen this yet.

I'm afraid I'm not going to be much help:(.  All the above suggestions seem reasonable.  The only other thing I could think of while brainstorming was the faint scar of an unusually stellate edrioasteroid, but I am unfamiliar with the possible taxa from that locality and their forms. (Isorophusella?) 

 

Screenshot_20180604-234430.thumb.jpg.1f5abec90324e1feae0bde898e91b03f.jpg

 

20180604_231617.thumb.png.1f86eec64ce9eaeec7c743fdd36403f6.png

 

I think its an unlikely possibility for a number of reasons.

 

Another possibility is that the star shape is pure coincidence and not biological.  

 

:shrug:

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doushantuo

Looks like an edrioasteroid to me

edit: an agelacrinid one

edit two: apologies to Peat,didn't see his post.He's got it right on the dot,obviously

alhhliftekkhhrnakristlanthc.jpg

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