Unknown fossil (myodocope ostracod?)

[Mainefossils]

I have been finding these small little fossils all through my specimens from the Leighton Formation, which is Pridoli. I suspect that they are myodocope ostracods, but I haven't found any ostracods that match it from my available literature. The specimen below appears to be an association of two valves. Each individual valve has a small protuberance in the middle, with two pits next to it; they are approximately 4 millimeters long, by 1.5 millimeters wide. 

 

The pictures below are first of photo with direct lighting, then a photo with raking light, to show the protuberances. Any help would be greatly appreciated! 

 

 

 

 

 

 

Edited June 18, 2021 by Mainefossils

[Rockwood]

I would have called it the internal mold of a relatively flat brachial valve from a brachiopod. Do you have a counter part to check ?

[Mainefossils]

1 hour ago, Rockwood said:

I would have called it the internal mold of a relatively flat brachial valve from a brachiopod. Do you have a counter part to check ?

Interesting. Unfortunately, the external mold was preserved in a soft crumbly siltstone, which, when I split the shale open, crumbled almost instantly. But, I have other specimens that are preserved in shale, which I have both cast and mold of, which I will post soon. Thanks so much for your help! 

[Rockwood]

It can be a bit like trying to adjust the picture on one of the old black and white TVs. 

[Fossildude19]

I'm wondering if these aren't some larval state of a bivalve/brachiopod? 

[Mainefossils]

So, I went through my fossils and found another specimen that shows the same characteristics as the first one. I now think that the first pair was not a cast, but an internal mold, as the external mold has a concentric pattern, and no protuberances. It is almost exactly the same size as the previous ones. The first photo is of the internal mold under direct light, the second photo is of it under raking light, and the third photo is the external mold under direct light. Raking light did not bring out any more details for the external mold. 

 

Thanks everyone for your patience! 

 

 

 

Edited June 18, 2021 by Mainefossils

[Rockwood]

15 minutes ago, Mainefossils said:

the external mold has a spiral pattern,

Spiral or concentric ? The distinction is critical.

[Mainefossils]

1 hour ago, Rockwood said:

Spiral or concentric ? The distinction is critical.

Sorry, I meant concentric.

[Fossildude19]

The last image looks like a bivalve, similar to something like Modiomorpha sp. 

[Mainefossils]

3 hours ago, Fossildude19 said:

The last image looks like a bivalve, similar to something like Modiomorpha sp. 

Thanks for your opinion! 

 

I checked our Modiomorpha, but it seems too big - this specimen is only 4 mm. I considered baby bivalves (also mentioned above), but I thought that young bivalves had very fragile shells which wouldn't fossilize well - is that correct?

 

I am still considering myodocope ostracods as a viable possibility, such as an Richteria. sp or a Cryptophyllus. I found ostracods that look similar, with the same concentric rings, in two articles, namely:

 

Pribyl, A. (1988) Ostracodes from the Silurian of Central Bohemia. Sbor. geol. Ved, Paleont., 29. 

http://www.geology.cz/sbornik/paleontologie/29/29-2.pdf

 

Perrier, V., Olempska, E., Siveter, D. J., Williams, M., Legiot, N. (2019) Silurian Myodocope Ostracods from Poland. Acta Palaeontologica Polonica, 64(2). 

http://agro.icm.edu.pl/agro/element/bwmeta1.element.agro-f94a5648-840a-4143-a621-68de552a59e2/c/379.pdf

 

Thoughts?

 

 

[Fossildude19]

Silurian is out of my wheelhouse - was just fishing for similar items. 

Could very well be ostracods - in fact, probably more likely than juvie bivalves.  

[Rockwood]

I can't best the ostracod angle.

[Rockwood]

I didn't find a hot trail, but apparently branchiopods do go further back than I thought.

[Mainefossils]

Thanks @Fossildude19 and @Rockwood! I will continue to look for literature on these little guys, and will keep you posted. Thanks so much for your time, patience, and help!

[Rockwood]

1 hour ago, Mainefossils said:

Thanks so much for your time, patience, and help!

Little secret; finding a way to patiently help is literally ancient medicine.