Lake Michigan Brachiopod?

[Pippa]

 

I found this little half-shell in SE WI. I think it is a brachiopod, but am not entirely sure. 

Originally it was more thickly encrusted, but I've given it a vinegar bath for about 2 days, and more details have now become visible. It is currently back in fresh vinegar, in the hope more of the crusty layers will dissolve.

I would appreciate your help with identifying the shell and also its interior visible parts if possible. For example, none of the anatomy drawings shows interior "separation walls" such as I see here. And specifically, what is that thick appendix sticking out the side of the shell? Its end looks like fossilized soft tissue to me. Is this the pedicle? If not, what is it? If yes, I thought soft tissue barely ever gets preserved? 

 

 

Interior

 

Side view

 

 

[doushantuo]

NICE!!

[Pippa]

6 minutes ago, doushantuo said:

NICE!!

I agree. Tiny but special! Especially, since it looked like nothing much when I found it.

[Rockwood]

3 hours ago, Pippa said:

. And specifically, what is that thick appendix sticking out the side of the shell?

Those are it's bryozoan buddies. 

[Fossildude19]

Looks more like an oyster than a brachiopod, to me.   

[Ludwigia]

I agree with Tim.

[Rockwood]

You're both crazy. From the Silurian ? and look at the internal side.

[fossilus]

Youngest fossils along lake Michigan would be Devonian.

[Kane]

We might wish to consider that this is not a fossil, but something more modern that might have been dropped there. I am seeing what I can judge by these photos a bit of the natural lustre on what I would expect to see on a non-fossil shell, and it seems possible that it simply became encrusted by being in the lake for some time as that process does not take too long.

[Rockwood]

Isn't this more typical of a brachiopod internal ? 

It has been soaked in a mild acid. The color (luster) doesn't seem a problem to me.

[Peat Burns]

I'm in the palaeozoic, likely Devonian, brachiopod camp on this one.

[Pippa]

14 hours ago, Rockwood said:

Those are it's bryozoan buddies. 

Haha, that's great! The only bryozoans I have are b/w lacy patterns on various mash type rocks. By naked eye the holes of the "appendix" just look like round pores. Blown up though, they ckearly are squarish. So yes, sure looks like you're right. 

10 hours ago, Fossildude19 said:

Looks more like an oyster than a brachiopod, to me.   

I assume oysters are bivalves then?   You guys can see, how little to nothing I know about shelled animals. The only shells I love to eat are scallops, and I recognize their shells.  Oysters, clams, mussels on the other hand make me gag and shudder...

10 hours ago, Ludwigia said:

I agree with Tim.

Tim being fossildude? Hi Tim!

4 hours ago, Rockwood said:

You're both crazy. From the Silurian ? and look at the internal side.

SE WI beaches have definitely different fossils than the Chicago area. The Milwaukee area is devonian. This little guy was found about 40 miles south of Milwaukee after a period of strong storms on a swimming (sand only) beach. Well that beach was covered in rocks, Big large ones to tiny pebbles. So I assume a little devonian shell could easily have been transported to that beach. 

4 hours ago, fossilus said:

Youngest fossils along lake Michigan would be Devonian.

Yep.

1 hour ago, Kane said:

We might wish to consider that this is not a fossil, but something more modern that might have been dropped there. I am seeing what I can judge by these photos a bit of the natural lustre on what I would expect to see on a non-fossil shell, and it seems possible that it simply became encrusted by being in the lake for some time as that process does not take too long.

Eh, I have a hard time believing this. How would the bryozon have turned into stone that quickly? And it IS stone, hard! Unmistakable. I believe the current freshwater bryozoans in Lake Michigan are modern invaders and hail from SE Asia and NE Africa. 

https://nas.er.usgs.gov/queries/greatlakes/FactSheet.aspx?SpeciesID=278&Potential=N&Type=1&HUCNumber=DGreatLakes

1 hour ago, Rockwood said:

Isn't this more typical of a brachiopod internal ? 

It has been soaked in a mild acid. The color (luster) doesn't seem a problem to me.

I've googled both bivalves and brachiopods for internal views, I didn't find a single photo or drawing showing these structures. Not knowing the term doesn't help, obviously.  I think I tried internal walls? separation walls? septae? just as in corals)  No luck. 

[Mark Kmiecik]

1 hour ago, Kane said:

and it seems possible that it simply became encrusted by being in the lake for some time as that process does not take too long.

By freshwater Bryozoans? Trust me, there's nothing in the Great Lakes that could produce that pattern!

[Pippa]

Thanks guys, what fun it is to read different people's take on these 2 little fossil buddies.

To think, that my little find caused such interest and diverse ideas...

What a great site and wonderful people!

 

Just wondering what @TqB would have to say...

 

 

[TqB]

7 hours ago, Pippa said:

Thanks guys, what fun it is to read different people's take on these 2 little fossil buddies.

To think, that my little find caused such interest and diverse ideas...

What a great site and wonderful people!

 

Just wondering what @TqB would have to say...

 

 

I'd guess brachiopod (and bryozoan) but have no idea which one - try googling "brachiopod septal plates" for a range of internal ridges. The slight depression you label in the first photo could be a sulcus.

The sheen does look oyster like but that might be a photographic artefact, along with the acid treatment.

[Wrangellian]

I don't know about that location but in my local Cretaceous there are brachiopods with sort of nacreous shell.

[Pippa]

21 hours ago, TqB said:

I'd guess brachiopod (and bryozoan) but have no idea which one - try googling "brachiopod septal plates" for a range of internal ridges. The slight depression you label in the first photo could be a sulcus.

The sheen does look oyster like but that might be a photographic artefact, along with the acid treatment.

Thanks for giving me the terminology to google more successfully. 

As to the lustre, that's interesting. I've never heard of "photographic artifacts" before.  But obviously, it's a real phenomene. I guess Newton Rings would qualify as well? I think the LED spots above my kitchen counter also might contribute to the shine. Everything does look fresher, cleaner and somehow sharper under them. They give of a very different light compared to fluorescents, incandescents or even halogens. 

 

20 hours ago, Wrangellian said:

I don't know about that location but in my local Cretaceous there are brachiopods with sort of nacreous shell.

 

Interesting. Just came upon this site:   http://inyo.coffeecup.com/site/brachiopods/brachiopods.html

 

Here is an excerpt of what "Inyo", the author of the website writes about two Devonian Period Brachiopods:
 

Quote

 

"Brachial and pedical views, respectively, of two Atrypa brachiopods I collected from the Upper Devonian Guilmette Formation, Nevada. At the horizon I explored several years ago, such Atrypa brachs weathered out by the "zillions" from well-exposed dark gray, thin-bedded limestones. The specimens are silicified, by the way, replaced by silicon dioxide, and imbued with minor amounts of iron minerals, which lend them an unusual pearly-golden glow."

 

 

 

        

 

 

 

 

And a description of a Pleistocene Epoch Brachiopod       (I have no idea if what the author describes below, is even possible:) 

Quote

"What's particularly fascinating about this Santa Barbara brachiopod is that the original shell material is preserved fully intact, without any kind of mineralisation (such as silification, for example)."

 

is 4

 

 

 

[Kane]

What makes me uncomfortable about a brach diagnosis is the symmetry aspect. I suspect that this is what prompted others to say "oyster." I'm happy you told us more about the piece and that it was rock-like (we can only do so much from photos!). As someone who is pretty much surrounded by three great lakes, this is not a piece I have seen (but my focus is on trilobites). I'd like to hear more from @Peat Burns as to why he sees this as a brach given the apparent symmetry issues.

[Pippa]

8 minutes ago, Kane said:

What makes me uncomfortable about a brach diagnosis is the symmetry aspect. I suspect that this is what prompted others to say "oyster." I'm happy you told us more about the piece and that it was rock-like (we can only do so much from photos!). As someone who is pretty much surrounded by three great lakes, this is not a piece I have seen. I'd like to hear more from @Peat Burns as to why he sees this as a brach given the apparent symmetry issues.

 

This is the first fossilized brachiopod or bivalve I've ever found at Lake Michigan that's not just tiny bits and pieces, or hidden to 99.9% in matrix.

I've never seen shellfish fossils at beaches in my area, other than barely recognizable parts in mash. But an hour north into WI, and fossils abound. 

And I go and pick up the one and probably only one that's not straightforward either brach or bivalve.   Figures  :-) 

 

[Rockwood]

2 hours ago, Kane said:

What makes me uncomfortable about a brach diagnosis is the symmetry aspect. I suspect that this is what prompted others to say "oyster." I'm happy you told us more about the piece and that it was rock-like (we can only do so much from photos!). As someone who is pretty much surrounded by three great lakes, this is not a piece I have seen (but my focus is on trilobites). I'd like to hear more from @Peat Burns as to why he sees this as a brach given the apparent symmetry issues.

I don't see a symmetry issue at all. Can you explain why you do ?

[Peat Burns]

6 hours ago, Kane said:

(but my focus is on trilobites). I'd like to hear more from @Peat Burns as to why he sees this as a brach given the apparent symmetry issues.

I think this is an incomplete / eroded valve of a brachiopod, which complicates visualization of it's original shape / symmetry. I think the features highlighted in the interior valve are not part of the valve but rather bits of other fossils. The shell appears to have a sulcus.  I've seen the silvery lustrous quality commonly on Devonian brachiopods around here, especially when the outer layers of the shell have been eroded or fractured away. 

 

Part of my assessment is also based on probability considering location, possible rock units, and relative abundance of brachiopods vs. bivalves in those units.

 

Of course I could be totalling wrong, but without holding the object in hand and putting it under my microscope, this is what I'm seeing/concluding based on the photo.

 

 

[Rockwood]

Creating a mental CT image from the three views does leave ample room for error. I could be over simplifying it. 

[Kane]

Thanks, @Peat Burns! I knew you'd get it in one.  

The apparent curvature of the plications was... throwing me a curve ball.  

I've seen the shiny nacreous appearance on mainly lower Devonian brachs, but the eye-popping shine from the photo seemed a bit different (the shine I see is generally more silvery, but this one could be an artifact of the camera and lighting). 

 

It will be neat to see once the OP has it completely cleaned up.

[Pippa]

7 hours ago, Peat Burns said:

I think this is an incomplete / eroded valve of a brachiopod, which complicates visualization of it's original shape / symmetry. I think the features highlighted in the interior valve are not part of the valve but rather bits of other fossils. The shell appears to have a sulcus.  I've seen the silvery lustrous quality commonly on Devonian brachiopods around here, especially when the outer layers of the shell have been eroded or fractured away. 

 

Part of my assessment is also based on probability considering location, possible rock units, and relative abundance of brachiopods vs. bivalves in those units.

 

Of course I could be totalling wrong, but without holding the object in hand and putting it under my microscope, this is what I'm seeing/concluding based on the photo.

 

 

@Peat Burns, you sure hit the nail on the head! 

I took the shell out of its vinegar bath today it became immediately clear that those ridges are not septal plates at all, but shell bits that are only connected to my shell by the limey deposit cementing them together.

Thank you Peat!

 

 

[Pippa]

8 hours ago, Kane said:

It will be neat to see once the OP has it completely cleaned up.

That's, if by the time it's cleaned up, there will still be something left of it... 

See, you might be overestimating my ability to not destroy that shell while trying to clean it up. It seems that every time I touch it, more of it is breaking off. That thing is super fragile.

Still, as you can see in the newest pic above, more cleanup is not really necessary to see that there are no plications, just two random shell shards sticking up and confusing (almost) everyone.

Maybe I'll continue the acid treatment to free the bryozoan from whatever will be left of the shell. 

 

What do you all think, can the bryozoan be ID'd further?  Leioclema? Rhombopora? Other?