A fossil freshwater snail inside a broken freshwater mussel

[Vopros]

Hi,

I wonder if somebody knows what a freshwater snail could have been doing inside a broken freshwater mussel? Was it feeding on it? Was it seeking a shelter in it, or it is just an accident? Has somebody here seen such or a similar fossil of one shell inside another broken one?

Thanks!

[Kane]

As this has been posted in Fossil ID, we would expect to see a fossil to identify.  

[Vopros]

20 minutes ago, Kane said:

As this has been posted in Fossil ID, we would expect to see a fossil to identify.  

Well, here it is. There is at least one and possibly more freshwater snails inside a broken mussel.

[hemipristis]

Interesting!

 

is the white material around it rock or soft sediment?

[Vopros]

2 hours ago, hemipristis said:

Interesting!

 

is the white material around it rock or soft sediment?

It is probably sandstone. It is not soft. There is also a black inclusion. Here are some microscopic images. Any idea what the black inclusion is?

[Rockwood]

Is this look common for fossils found in the area?  It looks suspiciously like synthetic casting resin to me.   

[Ludwigia]

Normally when marine fossils are found within other fossils, the former got washed into the latter after the death of the latter. If this one is sitting in a sandstone matrix then it definitely wasn't feeding.

[Vopros]

6 hours ago, Rockwood said:

Is this look common for fossils found in the area?  It looks suspiciously like synthetic casting resin to me.   

It is not plastic, it is opal from Lightning Ridge, Australia. It has some colors too. I am sure it is a fossil. Not to say that the seller did not even mention another shell [price redacted]

[Vopros]

4 hours ago, Ludwigia said:

Normally when marine fossils are found within other fossils, the former got washed into the latter after the death of the latter. If this one is sitting in a sandstone matrix then it definitely wasn't feeding.

It is not marine. It is freshwater.

[Rockwood]

36 minutes ago, Vopros said:

It is not marine. It is freshwater.

I think more detailed study of the depositional environment would be needed to make a difference. Events that would preserve animals in normal behavioral position are quite rare.

[Ludwigia]

49 minutes ago, Vopros said:

It is not marine. It is freshwater.

I figured you might say that. What I meant was, fossils formed in water. Sorry for the misunderstanding. I should have used the word acquatic I suppose. Anyway, that doesn't have any effect on my other statement.

[jpc]

6 hours ago, Ludwigia said:

Normally when marine fossils are found within other fossils, the former got washed into the latter after the death of the latter. If this one is sitting in a sandstone matrix then it definitely wasn't feeding.

I agree.  I also suspect it is marine.  Aren't the opal beds at Lightning Ridge derived from marine environments?  There are plesiosaurs and belemnites found there, for example.  The snail here does look like a salt water snail, but that is a half educated guess. 

 

Nice piece, nonetheless 

[Vopros]

Maybe there is more than meet the eye? Maybe it is a consumulite from a lung fish? Lung fishes do not get fossilized  (except teeth plates) but shells it ate could.  There are clearly more shells that those two we discussed before…

[TRout]

I agree with @Ludwigia's  comments above. Whether freshwater or saltwater, the most likely cause of these snails being found within the mussel shell is that the inhabitants of these shells died and the smaller snail shells were deposited within the larger mussel shell and then buried by sediment and later fossilized/opalized.

 

Also, while I don't have experience identifying these fossils (or any Australian fossils), my understanding is that Lightning Ridge produces mainly freshwater and estuarine fossils, while other opal beds produce marine fossils. 

 

Since you had asked if anyone had specifically seen an association of freshwater fossil snails within a mussel shell, here is an example that I collected myself: These are freshwater snails within a freshwater mussel shell from central California's Tulare Formation (Pleistocene to Pliocene). Again, the most likely explanation for this association is what was described above.

Edited January 23 by TRout

[Vopros]

2 hours ago, TRout said:

I agree with @Ludwigia's  comments above. Whether freshwater or saltwater, the most likely cause of these snails being found within the mussel shell is that the inhabitants of these shells died and the smaller snail shells were deposited within the larger mussel shell and then buried by sediment and later fossilized/opalized.

 

Also, while I don't have experience identifying these fossils (or any Australian fossils), my understanding is that Lightning Ridge produces mainly freshwater and estuarine fossils, while other opal beds produce marine fossils. 

 

Since you had asked if anyone had specifically seen an association of freshwater fossil snails within a mussel shell, here is an example that I collected myself: These are freshwater snails within a freshwater mussel shell from central California's Tulare Formation (Pleistocene to Pliocene). Again, the most likely explanation for this association is what was described above.

Thank you for your input and pictures! Here is the thing. I do not believe I have ever seen a few shells combined together from  Lighting Ridge. I did see a few  opal shells combined together from another location, where Marine shells  are found. Maybe it is because freshwater lakes and rivers do not have so much wave action to wash  out one shell into another. Anyway, I asked  a paleontologist from Australian Opal Centre, if this could be some kind of Coprolite or whatever. 
Here is her response:

The assemblage is unlikely to be a gastric pellet or coprolite from a lungfish because although lungfish eat molluscs, they grind them into small pieces with their toothplates.  I guess it's possible that the specimen is a regurgitate or gizzard content from a larger vertebrate, however this is speculative only and far from certain.

[JBkansas]

Lakes and rivers have waves and currents so it's most likely a random association (though it sounds like these are less common at the site, making it extra special). 

 

Some of the giant clams here have fish inside, not because they ate fish but because fish got trapped in abandoned shells during the event that buried them:

 

Edited January 23 by JBkansas

[rodrex]

Freshwater, those gastropods are freshwater live bearing (viviparid). I would say that they all washed together in a freshwater stream. The Griman Creek Formation is freshwater, with some occasional marine inputs. this is not the first time I have seen bivalves and gastropods intermixed.  You do get mass mortalities of those gastropods producing gastropod conglomerates.

 

Cheers R

Hamilition Bruce and Kear - LR snails.pdf

[Vopros]

6 hours ago, rodrex said:

Freshwater, those gastropods are freshwater live bearing (viviparid). I would say that they all washed together in a freshwater stream. The griman creek formation is freshwater with some occasional marine inputs. this is not the first time i have seen bivalves and gastropods intermixed.  you do get mass mortalities if those gastropods producing gastropod conglomerates.

 

Cheers R

Hamilition Bruce and Kear - LR snails.pdf 12.28 MB · 1 download

Thank you! The only thing that is bothering me with this “washed together” is that why there are no more of those from Lighting Ridge. I did see patches of shells from Coober Pedy, but I do not recall seeing one from Lightning Ridge.

[rodrex]

10 hours ago, Vopros said:

Thank you! The only thing that is bothering me with this “washed together” is that why there are no more of those from Lighting Ridge. I did see patches of shells from Coober Pedy, but I do not recall seeing one from Lightning Ridge.

Here are some images below that show what i talk about above. see the one with the 2 gastropods which has a cross section of a bivalve.

[Vopros]

1 hour ago, rodrex said:

Here are some images below that show what i talk about above. see the one with the 2 gastropods which has a cross section of a bivalve.

Nice! Did you find them yourself?