Fossilized crayfish gastrolith? ID help

[NEA Rocks]

I’m struggling to identify this. The closest I’ve found is possibly a fossilized crayfish gastrolith. But I could be way off. I’m very new to fossil ID. I do find a lot of marine life fossils in my area. I had thought perhaps brachiopod, but it looks nothing like my other one. I’ve included a photo of the unidentified piece along side my brachiopod so if I have misidentified it please correct me. Thanks in advance. 
Details:

Northeast Arkansas

Mississippi Alluvial plain 

Along the Eastern edge of Crowley’s Ridge 

I’m 93% certain the material is quartz (chert) 

 

 

[ClearLake]

First, your photography is very nice, excellent pictures. Unfortunately, I’m not sure either one of these is a fossil. I’ve never heard of a crawfish gastrolith, but it looks way to large to be in the stomach of any crawfish I have seen (or eaten). It bears a resemblance to an Ordovician bryozoan called Prasopora, but your geology is all wrong for that (unless it’s just some remnant from river transported gravel). I think it is more likely to be a worn and broken concretion. That does not look like any brachiopod I am familiar with, but it could have some fossiliferous remnants within a water worn rock. 

 

Crowleys Ridge has some Eocene deposits and most everything to the east of that will be Pleistocene and Holocene River sediments. 

[Rockwood]

3 hours ago, NEA Rocks said:

possibly a fossilized crayfish gastrolith. But I could be way off.

It may not be out of reach, but it would be quite a journey. Crayfish are freshwater crustaceans, and their gastroliths are composed of calcium carbonate.

[NEA Rocks]

1 hour ago, ClearLake said:

First, your photography is very nice, excellent pictures. Unfortunately, I’m not sure either one of these is a fossil. I’ve never heard of a crawfish gastrolith, but it looks way to large to be in the stomach of any crawfish I have seen (or eaten). It bears a resemblance to an Ordovician bryozoan called Prasopora, but your geology is all wrong for that (unless it’s just some remnant from river transported gravel). I think it is more likely to be a worn and broken concretion. That does not look like any brachiopod I am familiar with, but it could have some fossiliferous remnants within a water worn rock. 

Thank you for the compliment on the photos. I really put the effort in on them!

 

I appreciate the suggestion on the bryozoan. You may be on to something there. It gives me something to look into. 

 

on the brachiopod I guess I should have clarified it’s supposedly the internal cast. I’m not sure if that’s the right description. Only found 2 or three examples online- and I searched every which way i could think of! I’ll post a snapshot of the page that I got that info from. I’m not familiar with the source so I don’t know how reliable it is.

 

 

[Mahnmut]

Not sure about this one, 

When the structures are Brachiopod-typical I will not object.

but in Australia crayfish gastroliths are called yabbie buttons and happen to be replaced by opal, sometimes even precious opal.

So being replaced by silica is not unheard of. size is also plausible, just a bit on the big side.

Best Regards,

J

Edited February 15, 2023 by Mahnmut
spelling

[Ludwigia]

As previously mentioned, these things are much too large to be considered as crayfish gastroliths. I would however be open to the possibility that the one on the right in the last photo might have something to do with a brachiopod.

[Doctor Mud]

Well I just learned something. I hadn’t heard of crayfish gastroliths before! 
A clever way to conserve calcium in freshwater. 
 

TFF keeps on teaching….
 

 

Edited February 15, 2023 by Doctor Mud

[Mahnmut]

Ok, so marine palaeoenvironment lowers the probability of this being a yabbie button considerably.

[Rockwood]

7 hours ago, ClearLake said:

it looks way to large

I missed the cm indication. That would be one wallopin' crawdad. 

[Mahnmut]

52 minutes ago, Rockwood said:

I missed the cm indication. That would be one wallopin' crawdad. 

Agreed, most are below 1 cm, 1.5-2 seems possible, the OPs find is 2.8cm. If all other circumstances would fit I would not exclude it by size, but they don´t.

Best Regards,

J

[Rockwood]

51 minutes ago, Mahnmut said:

1.5-2 seems possible,

I bet it would uncomfortable though. 

[NEA Rocks]

So apparently I thought lobsters were also called crayfish lol… Here we call them crawfish (or crawdads) and somewhere I picked up that lobsters and crawfish were both crayfish, but I must’ve been mistaken on that fact.

Although I sure would love to find the hole that those mudbugs were hiding in!

I still don’t have the answer but you’re giving me some good clues to research. Feel free to keep throwing ideas at me! Turns out I’m better at hounding rocks than tracking down answers so I really appreciate the feedback. I love this community. 

[NEA Rocks]

7 hours ago, Mahnmut said:

Not sure about this one, 

When the structures are Brachiopod-typical I will not object.

but in Australia crayfish gastroliths are called yabbie buttons and happen to be replaced by opal, sometimes even precious opal.

So being replaced by silica is not unheard of. size is also plausible, just a bit on the big side.

Best Regards,

J

I came across some photos of some beautiful opal yabbi in my early searching and they were the only formations formations that resembled mine. Though it was a product page so I couldn’t find anything that gave me actual details like size. I searched expecting to find examples of yabbi from more common material like chert, but found nothing. 

Searches for crayfish gastrolith only turned up ones that are white and very small (naturally).
So thank you for clarifying. I was feeling very thrown off by what I was seeing. 

[Mahnmut]

Maybe @Budgie B can tell you more about yabbis,

in this thread he posted some of his gastrolith finds:

http://www.thefossilforum.com/index.php?/topic/113312-opalized-yabby-buttoncrayfish-gastrolith-or-something-else/

 

Although I do not think anymore your find is a gastrolith, being found in a marine environment.

If your round find is a Brachiopod like the other one, maybe @Tidgy's Dad has an idea, though there is not much detail to go on for an ID.

Best Regards,

J

 

[Rockwood]

4 hours ago, NEA Rocks said:

I thought lobsters were also called crayfish lol

A down east Maine Lobstah fisherman would call 'em bugs. 

[Doctor Mud]

2 hours ago, Rockwood said:

A down east Maine Lobstah fisherman would call 'em bugs. 

They have a type of crustacean in Australia they call a Morton Bay Bug. I thought they were talking about eating insects at first 

[Rockwood]

24 minutes ago, Doctor Mud said:

They have a type of crustacean in Australia they call a Morton Bay Bug. I thought they were talking about eating insects at first 

Downeasters don't use more words than necessary. Mosquito, Stink bug, horseshoe crab, lobster. Bug will do. 

[Doctor Mud]

22 minutes ago, Rockwood said:

Downeasters don't use more words than necessary. Mosquito, Stink bug, horseshoe crab, lobster. Bug will do. 

Similar to Australia - paramedic = Ambo, firefighter = Firey, politician = poly

[ClearLake]

On 2/15/2023 at 9:28 AM, NEA Rocks said:

So apparently I thought lobsters were also called crayfish lol… Here we call them crawfish (or crawdads) and somewhere I picked up that lobsters and crawfish were both crayfish, but I must’ve been mistaken on that fact

No problem. you have just (re)discovered the problem with common names (such as crayfish, crawfish, etc) and why the scientific world invented the whole binomial nomenclature thing for animals/plants/fossils/etc.  Common names may vary widely across a country and especially the world as multiple folks have given examples here.  Common names are fine and have their use, but can often lead to confusion when talking with others outside your area.  

 

But back to your two fossils.  I think you are right on the brachiopod, it is a very worn internal mold of a brachiopod shell.  I am familiar with the website you referenced, it is a very helpful one and I believe the author is a TFF member.  The other one, I'm pretty certain has nothing to do with any crustacean, may be a bryozoan, or may be a concretion type rock.  both of them, as fossils, are way out of their "home" where you found them in NE Arkansas, east of Crowleys Ridge.  I assume you are finding these in stream or other gravel deposits??  If that is true, they have been transported from somewhere north of you by the rivers, glaciers, or more likely a combo of the two (the continental glaciers of the Pleistocene did not reach as far south as you, but the strong outwash as they melted had a very profound impact on your area).  The point of all this is that they are out of their original depositional age and environment and have been very worn by the trip south and therefore identifying them becomes much more difficult.

 

You may find this publication from Mississippi on fossils in gravel of interest:

https://www.mdeq.ms.gov/wp-content/uploads/2017/06/Circular-7.pdf

[Tidgy's Dad]

I agree with the internal mold of a brachiopod for the one photo, I can make out what appear to be muscle scars and a median septum, the others I have no idea. 

[NEA Rocks]

On 2/16/2023 at 10:56 AM, ClearLake said:

No problem. you have just (re)discovered the problem with common names (such as crayfish, crawfish, etc) and why the scientific world invented the whole binomial nomenclature thing for animals/plants/fossils/etc.  Common names may vary widely across a country and especially the world as multiple folks have given examples here.  Common names are fine and have their use, but can often lead to confusion when talking with others outside your area.  

 

But back to your two fossils.  I think you are right on the brachiopod, it is a very worn internal mold of a brachiopod shell.  I am familiar with the website you referenced, it is a very helpful one and I believe the author is a TFF member.  The other one, I'm pretty certain has nothing to do with any crustacean, may be a bryozoan, or may be a concretion type rock.  both of them, as fossils, are way out of their "home" where you found them in NE Arkansas, east of Crowleys Ridge.  I assume you are finding these in stream or other gravel deposits??  If that is true, they have been transported from somewhere north of you by the rivers, glaciers, or more likely a combo of the two (the continental glaciers of the Pleistocene did not reach as far south as you, but the strong outwash as they melted had a very profound impact on your area).  The point of all this is that they are out of their original depositional age and environment and have been very worn by the trip south and therefore identifying them becomes much more difficult.

 

You may find this publication from Mississippi on fossils in gravel of interest:

https://www.mdeq.ms.gov/wp-content/uploads/2017/06/Circular-7.pdf

Thank you for the info!!

The brachiopod I actually found at a site on a high spot of Crowley’s ridge along with a good collection of artifacts. It has been suggested that the chipped spot of the brachiopod may have been where a hole was drilled to make a necklace which then broke at some point. Looking at the break up close I’d say that’s a likely possibility. So with that theory in mind the piece could have traveled from anywhere. 

The other unidentified piece is one of the very few rocks that I don’t remember exactly when and where I found it. Which is unusual for me, so there’s a chance it was added to my collection as a gift from my brother at some point. While everyone else in my life tolerates my hobbies, he’s the only one who actually contributes! Lol 

Though I have asked him and he doesn’t remember it either. So I will just enjoy it as a fun mystery I suppose. 

[Budgie B]

I find a lot of Yabby buttons ( greyfish gastroliths where I live in Oz and can say yours have completely different centre rings and shape to the ones I find, so I would have to say that’s a no for me. 
 

but I would really love to know why they’re call gastroliths in the first place? Does anyone have any idea where these little calcium buttons are located ? That might be a good story another day! 

[Mahnmut]

Hi Budgie B, 

although "gastro" most often refers to the stomach as an organ, it can simply mean abdomen, belly, tummy.

So its just saying belly stone.

Where exactly they form I will try to find out. -

 

Update: there are special tissues called gastrolith disks that sit on the inside of the shell, relatively far to teh front of the head where the gastroliths form.

Best Regards,

J

Edited April 11, 2023 by Mahnmut
additional info