piece of fin spine- Onchus or acanthodian?

[D.N.FossilmanLithuania]

Dear Guys,

 

Several years ago I found this piece of fin spine that is 3.5 mm width and by me it looks more similar to primitive shark like Onchus problematic fossils. 

Here is visible vertical groove texture and also oblique area of little oblong tubercles. 

The fossil is found in Late Silurian limestone erratic, the location was Varena town, South Lithuania.

Please help me to know, is it more like acanthodian or Onchus chondrichthyan?

 

Best Regards

Domas 

[Fossildude19]

This could be a piece of spine, or some bit of a skull. Many fish have squamation on skull plates. 

At the small size this is, I would think bit of a skull may be a better fit than spine. 
Just a guess, however. 

[Tidgy's Dad]

Not a clue, but it's very pretty! 

[Archie]

Cant help much other than to say the ornamentation does remind me a lot of many chondrichthyan spines Ive seen but not any acanthodian spines, amazing to see vertebrate remains of this age thanks for posting!

[D.N.FossilmanLithuania]

@Archie thank you very much for the opinion, I also think it is more shark like because here is specific ornamentation visible and the fragment is wide,

Silurian acanthodians were probably smaller. Talking about shark spines from Silurian there are two main possibilities- Onchus and also less likely Sinacanthus 

because sinacanthid sharks are also found in several different regions including China and Bolivia.

 

Best Regards

Domas  

 

[D.N.FossilmanLithuania]

Here is another one from Early Eifelian, 1.2 cm length and with long lower growth.

Please comment what do you think about this specimen. 

 

Best Regards

Domas 

[abyssunder]

I'm wondering if the second specimen can't be acanthodian fin spine.

 

excerpt from Jerve et al., 2017

[Pemphix]

I agree with fin spine on second one... 

[Archie]

I would have guessed the second was chondrichthyan rather than acanthodian but it would just be a guess, again very nice specimen!

Regards,

Sam