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Haragan Formation Brachiopod Unknowns


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Having just returned from a trip to Oklahoma, I tried identifying my finds from the Lower Devonian's Haragan Formation. Success was had except these five fossils. Any help is graciously accepted!











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Some nice Haragan fossils. Well done!  I would call #1 an Atrypa oklahomensis bsed on Oklahoma Geological Servey Bulletin 78.  Below is a part of Plate IX which shows the various forms of this species.  You can see the shape is slightly variable, but your length/width ratio and rib count look about right for the species.  I did not go research whether this one has been reassigned anywhere since this publication.




Not sure what #2 is, other than a very crushed brachiopod that essentially has collapsed within itself.


The best I can do for #3 is Orthostrophia strophomenoides.  The shape looks about right (see below) but the rib count on your specimen appears to be much less than what the publication describes.  What does yours look like in profile view?




Not sure what #4 is and agree that #5 is odd looking.  It doesn't look like a foram, but I have not found anything that does look like that.  Maybe @Al Dente  is right and it is not fossil, I'm not really sure.  The mineral wavelite is sort of similar, but not totally.  :shrug:

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@minnbuckeye, I think I now realize why the rib count seemed off to me on #3.  I should have gone and looked at my specimens first and then I would have realized sooner.  I think its a size thing.  I collected a bunch of Orthostrophia at White Mound, Oklahoma (not so many at Black Cat Mtn) and below is a growth series of Orthostrophia strophomenoides.  You can see the larger ones look just like the publication.  But if I read your scale correctly, the one you show is only about one Centimeter wide.  This would compare to the one second from the left below.  Smaller, therefore not as many ribs yet.  We  can see if @Tidgy's Dad has an alternate interpretation.




Here are my two smaller ones next to yours at about the same scale.


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1. Yes, I think it is still Atrypa oklahomensis.

2. I believe to be a rather squished Meristella atoka.

3. This one is the subspecies Orthostrophia strophomenoides parva.

4. :Confused05: Not a clue. Sorry.

5. Wow! I have never seen the like.

But I will say, because of my incurable brachiopod pareidolia, that they are inarticulate brachiopod dorsal valves.

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@ClearLake and @Tidgy's Dad, thanks for your input!! I am now convinced the brachiopod is Orthostrophia strophomenoides parva but included the requested photo anyways.



As for the Atrypa oklahomensis, I just thought it was too ornate.


So I am still stuck on #4 and #5. Here are a few different photos using different light for #5. I said this was from the Haragan Formation. In reality, it came from some grey blue clay close by. The only other fossils present were a few larger orthocone cephalopods. So I am assuming this rock was either just above or just below the Haragan. There was dozens of these specimens sitting on top of little mounds, easily picked up with the surrounding clay eroded away.




























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2 hours ago, minnbuckeye said:

As for the Atrypa oklahomensis, I just thought it was too ornate.

Yes, the "frills" are what's left of the lamellae that are common on Atrypa.  Most of the time they are worn away and/or broken off.  Yours is a fairly nice example where near the margin it looks like some of them are still preserved standing up and away from the shell surface.  The lamellae come in all types of development in different species of Atrypa and there is evidence in some of development into spines.  A paper here if you care to read any more:

Fenton, C. L., & Fenton, M. A. (1932). Alate Shell Lamellae and Spines in the Genus Atrypa. The American Midland Naturalist, 13(4), 203–221. https://doi.org/10.2307/2420269

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@ynot Thanks for an educated opinion!!! Will label these as likely selenite structures.

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