Unknown Pleistocene Fossil (Possibly Limpet)

[Pseudogygites]

Hi! I’m still trying to identify one fossil from a particular unit of Pleistocene/Early Holocene lacustrine silt from my hometown of Saskatoon, but I figured I would  look away from it for a bit to try and identify another fossil from the same unit I’ve been unable to classify. I have two specimens, both apparently of the same species. They are both approximately 0.5 millimetres across. They are perfectly circular, with lines radiating from the centre and rings of alternating colours (possibly representing growth lines). One specimen is photographed dorsally, showing its circular shape, the other in profile, showing its umbrella-like, protruding outline. All photos are taken through a microscope with my best camera currently available, an iPhone! My main areas of middling expertise are arthropod and vertebrate fossils, so I have no idea what this is! I have briefly studied fossil foraminifera and diatoms in the past, but it looks like nothing I’ve seen in those areas as well. It reminded me of a small limpet, some type of seed or spore, or perhaps even a strange fish scale, but I have no formal suggestions. I’d highly appreciate any help! I will try to supply any additional information you may need. Thank you!

Edited September 25, 2022 by Pseudogygites
Measurement error

[Pseudogygites]

I'm not even very confident in my pseudo-suggestion of limpet, it's just the only thing I've seen before that looks anything like this! "Limpets" are a group of many different families of Gastropoda which have independently developed the short, cone-like shell, and some are native to freshwater. Others can tolerate brackish or particularly salty water, which may or may not have been the case with this unit. Based on the size, this could only be a young or larval form, but if I recall correctly Gastropod hatchlings and juveniles look mostly like the adult equivalents, and this one lacks any type of coiling or spiralling. Most (if not all) of my initial suggestions are wrong, so I'm excited to see what the much more knowledgeable people here may think! To get the ball rolling, let's see if we can rule limpet out!

@FossilForKids

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@masonboro37

@PA Fossil Finder

@John Hamilton

@Wrangellian

@ted coulianos

@tmaier

@Micah

[Mahnmut]

Interesting little fossils. 

No idea what they are, but if they are lacustrine, that rules out limpets, as those are purely marine as far as I know.

Curious to hear more voices on this.

Best regards,

J

[Plax]

Any chance this is a modern contaminant? Don't know what it is but have seen it in screenings from Maryland where I assumed it was modern.

  Algal cyst?

Edited September 28, 2022 by Plax
additional information

[Plax]

didn't see an algal cyst in the google images that looked like this. Commenting o/n my own post...

[Wrangellian]

Sorry, I don't recognize it and my only guesses would be ones you've already mentioned. Anyway if it's Pleistocene/Holocene then it's possible that whatever it is might still be extant in your area, so if you know anyone who knows about modern lacustrine or terrestrial ecosystems in Sask, you might show it to them..

[IsaacTheFossilMan]

I'm going to say a diatom. cf. Stephanodiscus klamathensis.

 

From a completely different area, you can see similar diatoms of similar age in lacustrine environments: 

(PDF) Cyclotella petenensis and Cyclotella cassandrae, two new fossil diatoms from Pleistocene sediments of Lake Petén-Itzá, Guatemala, Central America (researchgate.net)

 

This article Atlas of diatoms (Bacillariophyta) from diverse habitats in remote regions of western Canada (pensoft.net) may be of direct help.

 

Note that diatoms are never considered "true fossils" as their cell walls are never replaced by another mineral.

Edited October 3, 2022 by IsaacTheFossilMan