Silurian Fish Remains

[Mainefossils]

I wanted to start this thread on the identification and discussion of silurian fish remains. I have been learning a lot about this subject, and hope to share my own finds and discoveries with you. 

 

I also hope that this thread will not only include my finds, but finds of all members of the Fossil Forum who have such materials, so that we may share our knowledge on these amazing fish. 

 

Some of our members( @jdp, ... ) are quite knowledgable on such finds, and I am looking forward to working with you guys more.  

 

On each post, please include size, stratigraphic data, and taxonomy, if known. 

 

I look forward to seeing your specimens. 

Edited April 25, 2021 by Mainefossils

[jdp]

I'm really really excited to see what you all have here! Silurian fish fossils are incredibly rare, and there are some very important evolutionary transitions that happened at that time!

[Mainefossils]

I'll start things off with three views of an acanthodian fish scale, most likely Thelodus parvidens. It is 200 microns long, by 250 microns wide by 200 microns deep. It is from the Leighton Formation, Maine. 

 

Literature on the species: 

 

Burrow, C. J.; Nowlan, G.; Turner, S; Denison, R.H.(2013) Silurian Microremains from the Silurian of Arisaig, Nova Scotia, Canada. https://www.researchgate.net/publication/258442501_Vertebrate_Microremains_from_the_Late_Silurian_of_Arisaig_Nova_Scotia_Canada

Turner, S; Burrow, C.J.(2018) Microvertebrates from the Silurian-Devonian boundary beds of the Eastport Formation, Maine, eastern USA. 

https://www.erudit.org/en/journals/ageo/2018-v54-ageo04224/1055415ar.pdf

Bremer, O; Jarochowska, E.; Marss, T.(2019) Vertebrate Remains and Conodonts in the Upper Silurian Hamra and Sundre Formations of Gotland, Sweden. 

https://www.tandfonline.com/doi/pdf/10.1080/11035897.2019.1655790

 

     

 

 

 

 

[Fossildude19]

Cropped and brightened:

 

[Mainefossils]

Thanks!!!

[Mainefossils]

@jdp, do you know of any records of Phlebolepis in the USA? Thanks!

 

[jdp]

I'm not an expert on thelodont biogeography, but I did a quick check on the PBDB and it looks like that taxon is restricted to the North Sea/Baltic region at that time interval (pale green dots):

 

 

I can do a deeper dive into the literature for you if you get back to me in a few weeks (I have an imminent thesis submission deadline coming up)

[Mainefossils]

Thanks so much for the response! I was curious because I found scales that are quite similar to Phlebolepis, of which I will post pictures soon. I thought that it was restricted to Europe, but was unsure. Thanks again!

[Mainefossils]

@jdp , here are the pictures of the supposed Phlebolepis sp. It is from the Leighton Formation, Maine, and is about 1.5 mm long by .375 mm wide. Here is the picture:

 

 

 

 

 

[jdp]

That seems a feasible ID. Very nice scale.

[Mainefossils]

53 minutes ago, jdp said:

That seems a feasible ID. Very nice scale.

Thank you! Do you know a specialist that I could submit it to for study?

[jdp]

I can ask around...my understanding is there's not a ton of people working on thelodont microfossils right now.

 

Alternately we could do some reading together and I can help you write this up.

[Mainefossils]

10 hours ago, jdp said:

I can ask around...my understanding is there's not a ton of people working on thelodont microfossils right now.

 

Alternately we could do some reading together and I can help you write this up.

Thank you so much! I would appreciate your help on a research paper. 

Edited May 14, 2021 by Mainefossils

[Mainefossils]

@jdp, would you prefer to carry this project out via PM, or on this thread?

[jdp]

Let's go to PM!

[Mainefossils]

Got it! 

[FossilDAWG]

On 4/25/2021 at 2:04 PM, Mainefossils said:

I also hope that this thread will not only include my finds, but finds of all members of the Fossil Forum who have such materials, so that we may share our knowledge on these amazing fish. 

 

Some of our members( @jdp, ... ) are quite knowledgable on such finds, and I am looking forward to working with you guys more. 

I hope it's OK if I take you up on your offer to post Silurian fish material here.

 

The specimens I'll post here came to my collection when Owen Dixon at the University of Ottawa cleaned up his lab and discarded fossils left behind by grad students over the years (this was back around 1982-83).  Almost all of these discards had become separated from their original locality data unfortunately.  All I know is that the lab was very involved in fieldwork studying mainly Silurian rocks on Devon and Cornwallis Islands in the Canadian Arctic Archipelago, in what is now known as Nunavit territory.

 

The first specimen is a solitary ostracoderm shield (33.9 mm long x 23.1 mm wide at the widest point):

 

 

The second specimen has several five complete or partial shields clustered on one rock, plus a worn shield on the other side.  The fossils are quite 3-dimentional, you can see that one individual at least preserves both the "top" and the "bottom".  The ones in the cluster are all 33-33.4 mm long by 17-18 mm wide, and the one on the bottom (visible mostly as an outline/mold with most of the "shell" eroded away) is 45 mm long by 23 mm wide.

 

 

 

 

 

Any suggestions about possible IDs and collection localities would be much appreciated.  @jdp, does any of this look familiar?

 

Don

[jdp]

whoa. those look like cyathaspids. I'll do some reading and get back to you.

[EMP]

Following @FossilDAWG's lead.

 

 

Onchus (??) sp. 

 

I have a few things from the Clinton Group (early Silurian) in central Appalachia. This is the best of the spines. 

[Mainefossils]

@FossilDAWG @EMP

 

Very nice!

 

@FossilDAWG

 

I found this article on a new species of cyathiaspid that was found in the Canadian Arctic. 

 

Elliot, D., Swift, S. L. (2010)  A New Species of Ariaspis (Agnatha, Heterostraci) from the Late Silurian of the Canadian Arctic. Journal of Vertebrate Paleontology, 30(6). 

https://www.researchgate.net/publication/233443086_A_New_Species_of_Ariaspis_Agnatha_Heterostraci_from_the_Late_Silurian_of_the_Canadian_Arctic

 

I cannot find the original description for A. ornata, but I will keep looking. I'm not sure it is possible to identify these specimens to species without being able to see the branchial opening. I think, though, that it is more probable to be A. ornata, because of the number of lateral lamina. 

 

There is a problem with this ID though, and that is that your head shields are very large. 

Edited May 17, 2021 by Mainefossils

[jdp]

That is very likely the exact species. It looks like Dixon collected extensively in that formation and area.

[FossilDAWG]

Thank you gentlemen @jdp @Mainefossils !  I now have a little bit of "light reading" to do.  I wonder if it might also be worthwhile to contact Dr Elliott to see what he thinks. 

 

Don

[Mainefossils]

@jdp @FossilDAWG

 

Thank you very much!

 

I also found this article, on Silurian fish from Canada. The species described, Vernonaspis major and V. epitegosa, seem to me to be another possibility. The size matches better with this genus, as well as the flat topped dentine ridges instead of sharp ridged. 

 

Broad, D. S, Lenz, A. C. (1972) A New Upper Silurian Species of Vernonaspis (Heterostraci) from Yukon Territory, Canada. Society for Sedimentary Geology, 46(3).

https://www.jstor.org/stable/1302975?Search=yes&resultItemClick=true&searchText=vernonaspis&searchUri=%2Faction%2FdoBasicSearch%3FQuery%3Dvernonaspis%26acc%3Doff%26wc%3Don%26fc%3Doff%26group%3Dnone%26refreqid%3Dsearch%3A1ae35c61c12fcc0b803d005f1594051b&ab_segments=0%2FSYC-5878%2Fcontrol&refreqid=fastly-default%3A6d14ea4943ddfbef7300d7687d773cfa&seq=1

 

I think that it would be a good idea to contact Dr. Elliot. If it is an Ariaspis, it is an abnormally large one that is possibly a new species. If it is an Vernonaspis, the genus has not been reported from Cornwallis Island as far as I know, and again, could be a new species. 

Edited May 17, 2021 by Mainefossils

[jdp]

Not sure. The texture looks more shell-y so I'd lean towards brachiopod (or pelycopod) but I couldn't say with certainty.

[Mainefossils]

Thanks!