Fossil Pleistocene Fish Scales(?) From Saskatoon

[Pseudogygites]

Hello! Thank you all for taking the time to read this and (hopefully!) help me identify a very interesting find from Saskatoon! I was on a fossil hunting trip to a local exposure of  Pleistocene glacial lake sediments in Saskatoon, and I took home a few samples of it to review later. While looking through one piece (the material is silt but breaks like a rock and is somewhat laminated), I saw this very strange shape. Attached are a few images, some simply in situ, others through a microscope. My apologies if the image quality is not ideal, I do not currently have any better equipment. There are a few images with my fingernail in frame to give you a sense of scale; this thing is very small. It is a kind of dome shape adorned with concentric rings of linked “nodes.” When looking at it, I knew it couldn’t be a pebble or partially buried rock. The thing it reminded me the most of was a Ptychodus tooth or other fish tooth plate, but the “dome” the nodes sit upon is penetrated open in one spot and is hollow. While I suppose this doesn’t rule tooth out, it does make me doubt that possibility. In addition, the nodes appear to resemble fish scales, especially ganoid scales, as some are rhomboidal in shape and all have the glassy coating those scales tend to have. There is also what appears to be a bone fragment near the dome. This is where my own suggestions end, I have no other ideas as to what this weird thing might be! Simple confirmation of the nodes as fish scales would probably satisfy me, but identification of them as ganoid would be even better. Please let me know if I can provide any extra clarification! Thank you! 

[hemipristis]

ah, young eyes... lol

[Pseudogygites]

3 hours ago, hemipristis said:

ah, young eyes... lol

Haha! Is it obvious? Obviously nothing, or obviously something? My eyes are young, but so is my brain!

[RuMert]

hemipristis probably meant it's not that easy to spot such a small object when you are not so young  Actually it happens after 40

[FossilDAWG]

It is clearly "something" organic, but it doesn't resemble any fish scale I am familiar with.  Interesting...

 

BTW do people commonly find fossils in those Pleistocene lake clays?  My understanding was that they are usually barren.

 

Don

[Pseudogygites]

2 hours ago, FossilDAWG said:

It is clearly "something" organic, but it doesn't resemble any fish scale I am familiar with.  Interesting...

 

BTW do people commonly find fossils in those Pleistocene lake clays?  My understanding was that they are usually barren.

 

Don

Interesting indeed! I've never seen anything like it! To answer your question, the idea that the Quaternary glacial/lake clays (and the north/central part of Saskatchewan in general) are completely devoid of fossils is a pervasive one, but it seems that people have rarely (if ever) studied many of them closely or for very long, and the fossil content can vary with the lake deposit in question. For example, there is a Lake Agassiz deposit in Manitoba (wish I could remember the paper) that is quite productive of gastropod shells and the like. I've also seen lacustrine deposits of the same age here that produce absolutely nothing. Also, it is a fairly common occurrence for farmers or construction crews to suddenly "dig up" a mammoth skeleton or isolated bone in this province and others. Information about the geologic origin of these specimens is rare, but I suspect they are found when fossil-bearing layers of such deposits are partially exposed, but the exposures disappear as quickly as they are discovered. Our entire provincial paleontological history has essentially been focused on the Mesozoic deposits in the south, but throughout my time here I've been absolutely fascinated by these large swaths of unexplored deposits. Sometimes I find nothing (things like that are probably the reason why these deposits are thought of as barren), other times I find something like this! There was one lacustrine deposit I studied that produced abundant carbonized plants, diatoms, and invertebrate traces. Another produced a few mammal bones. The layer this specific thing came from also has carbonized plant fragments and one spiral-shaped foraminifera so far, and I've only studied five pieces of it. All in all, I think these types of sediments largely have a preservation bias against all fossils for whatever reason, but that doesn't mean there aren't exceptions.

[Pseudogygites]

Update! I’ve taken some more pictures at some different angles and magnifications, revealing some more details. The “bone fragment” connected to the nodes does not have the usual semi-smooth texture of bone, but is covered in many visible raised bumps (seen in the picture as spots of light). On each side of the specimen, there is a “rib” hemming the nodes in. The “rib” is a long, curved, singular structure similar in texture and appearance to the “bone fragment.” On the back of the specimen, the nodes or “scales” fuse. That angle is now shown in a few of these pictures. It is my hope that these extra details might help us to at least determine what material this is (bone, scale, tooth, etc), which might help us further identify it.

 

 

 

Edited September 23, 2022 by Pseudogygites

[hemipristis]

14 hours ago, RuMert said:

hemipristis probably meant it's not that easy to spot such a small object when you are not so young  Actually it happens after 40

              

That is indeed what I meant.  I'd need a magnifying glass and my reading glasses to see it  

[Pseudogygites]

Further update! I have been in contact with a good friend of mine who studies ichthyology. At her own admission, she does not know absolutely everything about fish anatomy, but she has been studying this for years now. When showed a few pictures of the specimen without any other information, she suggested reasonably confidently that they were placoid scales, specifically likely from a chimaera or ray. Salt water fish would, generally speaking, not be able to survive in the lake environment. Also, since Saskatoon is pretty much as landlocked as is physically possible, it would be quite the trip! As @FossilDAWG pointed out, they look very unusual for fish scales, and my friend even suggested this suggestion may be inaccurate. However, I'm going to pursue this suggestion, as I don't have any other leads at the moment! It also makes me wonder if the "bone fragment" could, in fact, be cartilage. Maybe some experts on fish mouth plates, chimaeroids, rays, fish scales, etc. on the forum could help!

@oilshale

@will stevenson

@MarcoSr

@digit

[digit]

Very cool find! Definitely an interesting fossil but well outside my bailiwick. Looking forward to seeing if we get a good match for an ID on this one.

 

 

Cheers.

 

-Ken

[Coco]

I didn’t see the size of your object.

 

Coco

[Pseudogygites]

7 minutes ago, Coco said:

I didn’t see the size of your object.

 

Coco

I'm trying to find a way to get a picture with a ruler included right now. Stay tuned!

Edited September 23, 2022 by Pseudogygites

[Pseudogygites]

12 minutes ago, Coco said:

I didn’t see the size of your object.

 

Coco

The scale is in centimetres! The object is the round, circular, dark coloured object directly to the right of the ruler.

[Coco]

OK, 1 mm !

 

Coco

[FossilDAWG]

If 1 mm, perhaps an ostracod?  Can we exclude a seed of some sort?

 

Don 

[Pseudogygites]

3 hours ago, FossilDAWG said:

If 1 mm, perhaps an ostracod?  Can we exclude a seed of some sort?

 

Don 

With the particular asymmetry of this specimen combined with its distinct preservation compared with the other plants from this unit, I’d say seed is unlikely. However, I think you’re right on the money with ostracod! I was only familiar with the stereotypical smooth, seed shaped morphs, but after some research I’m stunned by the real diversity of this group! I haven’t found an exact match, and I likely never will with the resources I have and the number of species, many without photographs, of ostracods, but I have found many near perfect matches! For example, this fossil ostracod below. The concentric rings of nodes match up almost exactly, down to the way they fuse with the edges of the shell. I can’t photograph this region, but there is one portion of the specimen composed on one fused plate of material with many pits in it, exactly like some of these ostracod shells. This also explains how the nodes seemingly fuse, as fish scales never really do. We’re not looking at many things floating on top of sediment, we’re looking at one shell partially buried by sediment, with the low points filled in! Now that I at least think I know now what kind of animal this is, I can really appreciate the pristine preservation!

[Al Dente]

8 hours ago, FossilDAWG said:

Can we exclude a seed of some sort?

Seed was my first thought when I saw this.

 

 

Edited September 24, 2022 by Al Dente

[MarcoSr]

The raised ridge zigzag pattern and the shape of your specimen doesn’t match any shark placoid scales (see below picture) (dermal denticles) or any ray placoid scales (dermal denticles), dermal thorns or scutes that I’m familiar with.  Bony fish scales (see below picture) have concentric annual/growth rings which your specimen doesn’t have.  Chimaeras have smooth and naked skin, lacking placoid scales except in the claspers.

 

The only places I have seen this raised ridge zigzag pattern is on various shark tooth (crushing type teeth) crowns, in softshell turtle shell, in some flat, very thin, bony fish specimens (not sure where on the fish they are from) that I have and in some fossil seeds that I have donated.  I think a seed is a definite possibility.

 

 

 

Marco Sr.

[FossilDAWG]

Time for a bit of a reality check I think, as it's clear people are not familiar with the geological context of this fossil.  These clays were deposited in large cold freshwater lakes that formed south of the melting glaciers, or as a result of north-flowing rivers being blocked from reaching the Hudson's Bay or Arctic Ocean.  The clay is derived from very fine pulverized rock produced as the glaciers were advancing.  As the glaciers melted till and coarse material was deposited as drumlins, moraine, or till and sand beds.  Fine particles could remain suspended in water and be transported far from the melting glaciers.  Often these clay beds that formed in large glacial lakes are varved: in the summer there was an influx of sediment with a range of particle sizes, but in the winter the lakes would freeze over blocking that influx, so deposition was from the finest particles that could remain suspended in the water for a long time.  As a result you see annual varves, layers that alternate relatively coarse layers formed when the lake was open water with very fine sediment layers formed when the lake was frozen over.

 

So to recapitulate a bit, this fossil was found in a late Pleistocene cold freshwater lake deposit.  Any marine or tropical organisms can be excluded.

 

There are a number of freshwater ostracods that inhabit cold freshwater environments.  There are also some fish, such as char, grayling, etc that inhabit these lakes.  As well vegetation would colonize the land around these lakes. The literature on arctic lakes and flora would be a good place to look to try to ID this interesting fossil.

 

Don

[Pseudogygites]

Wow, there's nothing like refreshing one's thread and finding a bunch of new replies! Thank you all for the valuable insight and information! @Al Dente, do you know what kind/species of seed is shown in that photo? The resemblance is somewhat uncanny, if not exact. I might look into that family of plants to see if I can find an even closer match! @FossilDAWG, thank you as always for the truly comprehensive and helpful info! @MarcoSr, thank you for the info on fish scales as well as that image! Fish fossils are sometimes also known from sediments like this, so it's quite possible your input will be very very helpful in the future!

[Al Dente]

9 hours ago, Pseudogygites said:

do you know what kind/species of seed is shown in that photo?

They are raspberry seeds. They were the first wrinkled seeds I found in a Google search. There are probably hundreds to thousands of species of plants with wrinkled seeds.

[Pseudogygites]

Many thanks to all who have responded to this thread!  I'm torn between ostracod or seed. As detailed in the response above, the patterning on the shell is nearly identical to an ostracod, but the shape is a bit unusual. Ostracod valves have more-or-less straight edges (hinges), at least as far as I'm aware, and yet this fossil has strongly curved edges. It's hard to describe its exact shape, but to use an analogy it looks like a Gryphaea or an enrolled trilobite in profile more so than an ostracod. Maybe the valve has been deformed by pressure? Both ostracod and seeds are usually bilaterally (or radially, in the case of seeds) symmetrical, and I can't imagine how this thing could be one half of something symmetrical with its extremely concave edges. Maybe geological deformation is the best explanation. Thoughts?

[Pseudogygites]

New update! After even more research and comparison, I now believe this is in fact a seed, as @Al Dente and @FossilDAWG suggested! It explains the unusual morphology that doesn't fit an ostracod and the rows of knobs and raised edges, as many seeds I've now seen have. I haven't found an identical match yet, but it seems to be similar to seeds of plants like Saponaria, Silene, Stellaria, and Cerastium. I'll spend the next little while trying to find a closer identification somehow, while I also try to identify some invertebrate fossils from this same unit!