Fish Coprolite?

[Mainefossils]

I have read in multiple papers that there are three theories to the preservation of thelodont scales. First, a rapid burial when the thelodonts have died under still circumstances, e. g., in a lagoon or other still body of water. This results in associated scales. Second, the thelodonts die  and disintegrate in the open ocean, leaving behind disassociated scales. Third, the thelodonts were eaten, and deposited as coprolites. 

 

Now, I have just found an array of thelodont scales in a single small spot. The stone they are preserved in is a lighter color than the rest of the shale. The majority of the scales are Phlebolepis elegans, with one being of a Thelodus parvidens. I was wondering if it could be an example of a coprolite? 

 

It is from the Leighton Formation, Maine; which is Pridoli, Silurian. The pictures below first show the cross section of the specimen, and then the top of it. I will take pictures of the individual scales as soon as possible. It is rather hard to see the cross sections in the pictures, but the bluish pieces are thelodont scales. Unfortunately, I don't think it will be able to be prepped without destroying some of the details. 

 

Thanks in advance for your help!

 

@GeschWhat @Rockwood @jdp

 

 

 

 

 

[Fossildude19]

Another possibility to consider is regurgitant.

[Mainefossils]

Thanks for your opinion! It makes me wonder, though, whether there is any evidence pointing to Silurian fish doing this? I'll be interested to hear what others say about this. Thanks for your help! 

[abyssunder]

3 hours ago, Fossildude19 said:

Another possibility to consider is regurgitant.

Not a bad idea, in my opinion. 

[Rockwood]

I could have thousands of them. I'd never know it. 

[westcoast]

7 hours ago, Rockwood said:

I could have thousands of them. I'd never know it. 

Yes, i've recently been finding a lot of potential examples i had overlooked previously.

[jdp]

The phosphatic material surrounding the scales does make me think possible regurgitant. If it was a coprolite, you'd think there would be traces of the spiral valve.

[Mainefossils]

17 minutes ago, jdp said:

The phosphatic material surrounding the scales does make me think possible regurgitant. If it was a coprolite, you'd think there would be traces of the spiral valve.

I was thinking that if it were a coprolite, it could be from something like an acanthodian, whose coprolites do not have a defined shape. Do acanthodians, or for that matter any Silurian fish, have spiral valves? I have read that the "spiny sharks" had a physiology and morphology similar to sharks, but I don't think any specimens that exhibited soft body preservation have been found. In this case, would a coprolite still be a possibility for this specimen?

 

Please understand that I am not arguing with you - just picking your brain to try to understand more about such specimens. Thank you for your time and patience!  

[jdp]

Chondrichthyans have a spiral valve. Early osteichthyans up through relatively advanced stem-group tetrapods have a spiral valve. Placoderms seem to have had a spiral valve. So it seems reasonable to assume that acanthodians had a spiral vale.

[Mainefossils]

Just now, jdp said:

Chondrichthyans have a spiral valve. Early osteichthyans up through relatively advanced stem-group tetrapods have a spiral valve. Placoderms seem to have had a spiral valve. So it seems reasonable to assume that acanthodians had a spiral vale.

Thanks for the info! 

[jdp]

no problem!

[GeschWhat]

 

On 7/5/2021 at 2:20 PM, jdp said:

Chondrichthyans have a spiral valve. Early osteichthyans up through relatively advanced stem-group tetrapods have a spiral valve. Placoderms seem to have had a spiral valve. So it seems reasonable to assume that acanthodians had a spiral vale.

I haven't heard anything about stem-group tetrapods (not sure what you mean by this group) and placoderms having spiral valves. Is this something new? If so, have these findings been published?

 

Your find does give off a bromalite vibe. It would be hard to determine whether it is a regurgitalite or eroded/dissolved coprolite. Either way, it's is a wonderful find!

[jdp]

I don't remember the placoderm reference offhand but the aistopod Lethiscus is described as having a spiral valve by Wellstead (1982) and that animal is stem tetrapod according to, well...me, in Pardo et al (2017). There might be some records for tristichopterids and rhizodonts as well but I don't remember those offhand.

 

By stem group I mean animals related to tetrapods but not descended from the last common ancestor of modern amphibians and amniotes.

Edited July 8, 2021 by jdp

[doushantuo]

Jdp,could the placoderm reference have been a piece by Goujet?

[jdp]

Could have been

[Mainefossils]

Thanks for all the information, @GeschWhat and @jdp!

 

I have just finished taking pictures of the bromalite. The pictures below are both of the bromalite. The first picture is of the left of the specimen, and the second of the right. The first picture shows three scales of P. elegans. The second picture shows two scales of P. elegans, and one of a T. parvidens. The T. parvidens is near the middle of the picture. It is a small round scale, with very little ornamentation on the crown. There is a possibility of it being a worn oral scale of a P. elegans, but I am not certain. 

 

Thanks everyone for reading!