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Ordovician fossils from the Nicolet River Formation, Laprairie, Quebec


Jeffrey P

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Found these on Tuesday at the Hansen Brick Quarry in Laprairie which is just minutes from downtown Montreal. In addition, found a number of bivalves, gastropods, crinoid pieces, brachiopods, and a few partial and one complete Flexicalymene trilobite.

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Thought this might be a piece of nautiloid shell, but have never seen ornamentation like this.

post-13044-0-54001000-1446394494_thumb.jpg

Not sure what this is. Thought it might be a bryozoan covering (something?).

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Here's another view:

post-13044-0-41993900-1446394628_thumb.jpg

This I think is a bryozoan covering a Hormotoma gastropod:

post-13044-0-54055800-1446394783_thumb.jpg

I would appreciate your input. Thanks.

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Hey Jeff,

Neat finds.

I am thinking orthocone possibly, ...on your first item?

The second item is either a bryozoan covering a gastropod, or a "squish-out" of a gastropod.

I found several similar at Deep Springs Road, the gastropod being Paleozygopleura, instead.

Will be interesting to see what others have to say.

Regards,

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Thanks guys. I thought about glass sponge, but when did they first appear? The only other glass sponges I have are Upper Devonian.

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Thanks guys. I thought about glass sponge, but when did they first appear? The only other glass sponges I have are Upper Devonian.

They got their start in the Ediacaran, but the ones your specimen most resembles are indeed Devonian.

Any of that stratum in the area?

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They got their start in the Ediacaran, but the ones your specimen most resembles are indeed Devonian.

Any of that stratum in the area?

No. It is definitely Ordovician. I'm guessing there isn't any Devonian around for at least a hundred miles. Plus the rock type, and other fossils on the matrix matches the other stuff in the quarry.

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There are listed some Hexactinellid sponges from the Ordovician, but images are hard to come by.

I suppose it could be a rugose 'horn' coral, weathered just right, but the cheesecloth pattern is just so compelling!

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It appears to be a straight cephalopod. Foerste's figures of Spyroceras hammelli have similar striations:

 

IMG1.jpg

 

Foerste, A.F. (1924)
Upper Ordovician faunas of Ontario and Quebec.
Geological Survey of Canada Memoir, 138:1-255
 
 
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"Spyroceras" was at one time used for all orthoconic nautiloids with ornament that consists of both concentric annulations (ribs) and longitudinal striations (oriented with the long axis of the shell). Spyroceras is now (as I recall) restricted to some Devonian species, based on internal structures shared with the genotype. Ordovician shells with this ornament are assigned to Gorbyoceras and Anasypyroceras; Spyroceras hammelli is now assigned to Gorbyoceras, for example. I would tentatively identify Jeffry P's specimen as a Gorbyoceras sp., as the longitudinal striations cross over the top of the annulations and in Anaspyroceras they are seen in between the annulations but not crossing the crest. However this is not a very good character, as any wear will remove the striations from the crest of the ribs. The difference between the genera is actually based on the spacing of the ribs compared to the suture lines, but we can"t see this feature in the photo.

The "bryozoan" on the gastropod shells is a bit of a mystery, at least to me. I have a lot of specimens of gastropods and bivalves that show this, collected from shales in the Ottawa Ontario area (Carlesbad Formation) that is equivalent to the Lorraine exposed in the Hanson Pit. The feature is not bryozoan, as there is no evidence of zooaria (small holes representing the tubes of individual animals in the colony). I have heard these features described as algae/biofilms growing on the dead shells, and also as purely sedimentary features produced as the soft fine mud distorted and sheared around the shell as the sediment dewatered and was compacted under pressure.

Don

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Thanks Don, Herb, and Scott. Not only a good suggestion on the genus, but a lot of other excellent related info. as well. You guys know your stuff.

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Don is right.

Here are also some specimens, Gorbyoceras hammelli (which is the same specimen from the UGA Stratigraphy Lab) and Anaspyroceras cf. A. cylindricum, in document Middle and Upper Ordovician Nautiloid Cephalopods of the Cincinnati Arch Region of Kentucky, Indiana, and Ohio - by Robert C. Frey, Plate 12.

Gorbyoceras hammelli post-17588-0-31820000-1446425596_thumb.jpg

Note: For better/clearer pictures use the pdf document linked (ebook-free/download pdf) from wich I couldn't extract and transform the picture to jpg because it is protected.
https://books.google.com/books?id=HOu8p7kPgfkC&pg=SL16-PA2&lpg=SL16-PA2&dq=Middle+and+Upper+Ordovician+Nautiloid+Cephalopods+of+the+Cincinnati+Arch+Region+of+Kentucky,+Indiana,+and+Ohio&source=bl&ots=e5uZ3ckkRK&sig=QGRuCRyI1fPYNg-a3kHSNGLsQbc&hl=en&sa=X&redir_esc=y#v=onepage&q=Middle%20and%20Upper%20Ordovician%20Nautiloid%20Cephalopods%20of%20the%20Cincinnati%20Arch%20Region%20of%20Kentucky%2C%20Indiana%2C%20and%20Ohio&f=false

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Don is right...

Whoops! I posted the same info 3 hours earlier. Spyroceras (=Gorbyoceras) hammelli

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Also you are right!

I was looking to find another picture from other source, capable to show the necessary comparative details. :)

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Another point in doubt of the bryozoan covering idea would be the linear aspect. Large encrusting colonies achieve this degree, but it seems like a small colony on an object like this would have a pattern more consistent with earlier astogony.

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  • 4 years later...

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