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Trying to identify


CuriousCollector

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Welcome to TFF!

Looks like a orthocone nautilus. Nice find!

Tony

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CuriousCollector

It is from Milwaukee Wisconsin. I found it in my grandmothers garage  over 20 years ago close to Lake Michigan. The great lake area is the best guess i can share.

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Splendid orthocone nautiloid. It's a keeper for sure. Make sure you keep with it a piece of paper recording everything you know about it, especially the location of origin as accurately as you can get it.

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Excellent example of an orthocone cephalopod ! :) 

 

orthocone_nautiloid.jpg

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CuriousCollector

Thank you for the thoughtful information and complements. :1-SlapHands_zpsbb015b76: I can finally start learning more about it and piece by piece. Thank you.

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CuriousCollector

Dawsonoceras!! This looks like a petfect match! The images and what i have are identical! 

1 hour ago, Fossildude19 said:

Dawsonoceras sp. might be a closer match.  

 

IMAGES

 

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There appears to be some trace of longitudinal striations (running the length of the specimen) as well as the prominent ribs.  This ornament is consistent with Dawsonoceras, a Silurian genus found in Wisconsin (and elsewhere).

 

In the past some nautiloid genus names were based on one or two surface features, and so they ended up being applied to many species extending over very long periods of time.  Spyroceras was one of these; the name was applied to every orthoconic (straight or slightly curved) nautiloid with strong ribs completely encircling the shell.  Used this way, the name applies to many hundreds (maybe thousands) of species extending from the Ordovician to the Permian.  This genus definition completely ignores internal features such as the structure of the siphuncle, organic deposits within the cameral chambers, surface features such as longitudinal striations, and so on.  A more biologically realistic taxonomy makes use of all the features of the shell.  The siphuncle is especially important; this structure is internal and so is less influenced by external environmental forces, and so it more accurately reflects taxonomic relationships.  On the other hand exterior features such as ribs function to strengthen the shell, and so the same (or closely similar) features can evolve wherever environmental pressures are similar.

 

As a result, "Spyroceras" of old has been divided into many (perhaps hundreds) of genera.  The name Spyroceras is still valid, but now it is limited to a small number of Devonian species including the "type species" and close relatives.  When someone describes a new genus, they have to designate a "type species", which is the single species the author considers to be the best representative of their genus concept.  Of course, when someone describes a new species they have to designate a holotype, which is an actual specimen they consider to be the best example of the species. [note: in many cases "best" means "only", not necessarily a specimen that shows all the features to perfection, which can cause confusion later on.]  Anyway, that means that when we want to know what Spyroceras really is, we should be able to study an actual specimen that best exemplifies the features of the species that best exemplifies the genus, in the mind of the scientists who first named the genus.  Any species that differ significantly cannot be included in Spyroceras, and so a new genus has to be named and described to accommodate them.  The type species of Spyroceras, Spyroceras crotalum Hall 1879, was described from the Devonian of New York State, and it also occurs in Russia. 

 

Note that this system requires that actual specimens be preserved so that they can be re-examined many years after the original paper was published.  Many times, the original written descriptions (and illustrations) are completely inadequate in modern terms.  Commonly internal features of the shell are not mentioned at all.  This is why species (and other taxa) should not be described based on specimens in private collections.  It is almost impossible to assure that specimens in private collections can be located and studied 20 years from now, much less 200 years.  Occasionally someone will "bend the rules" perhaps based on a promise that the specimen will be willed to a museum once the collector dies.  These arrangements often don't work out as the specimens disappear or the collector does not write the donation into their will (and so the family keeps it or sells it privately).  Now we have a species without a type specimen, which means we don't really know (and can never know) all the features of the species.  If it is rare (which generally the case) other specimens, collected perhaps many years later, cannot be directly compared to the type, and the researcher must choose between using a species name that she cannot be completely confident is correct, or describe a new species and designate the new specimen as the type (assuming it can be preserved in a museum collection).  The latter course is more correct, but now multiple names of varying certainty can be applied to what is probably one biological species.  That is why when private collectors find a new species, if they want that species to be described and published they must be willing to donate it to a properly curated museum collection.

 

That's a lot of discussion based on "Spyroceras", but I think it's worth repeating the message from time to time.

 

Don

 

 

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Don, 

Thanks for the great explanation. 

It seems there were many "lumpers" in the old days of Paleontology.

Not surprising, I guess.

I appreciate the discussion you present here.

Regards, 

 

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What I remark interesting is the color pattern of Dawsonoceras annulatum shells, described in Stěpán Manda, Vojtěch Turek.Colour patterns on Silurian orthocerid and pseudorthocerid conchs from Gotland - palaeoecological implications.Estonian Journal of Earth Sciences, 2015, 64, 1, 74-79. pdf

 

" A shell of the orthocerid Dawsonoceras annulatum (Sowerby) exhibits relatively broad longitudinal colour bands around the entire shell circumference, which in combination with transverse annuli and undulated growth ridges form a visually reticulate ornament. Such a combination is not known in other Silurian straight-shelled cephalopods. "

 

0001.jpg

 

 

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Other than not having detailed location information that is one excellent specimen.  All too often the distal (tip) of the orthocone is not preserved.  Good stuff indeed.

 

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It sure is great to read all this paleozoic expertise here. I'm just an amateur in comparison. Perhaps CuriousCollector could take a photo of the fat end of the orthocone so that maybe the siphuncle could be studied?

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I am a Paleozoic idiot... I thought it was just a spoon.  

 

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CuriousCollector
2 hours ago, Ludwigia said:

It sure is great to read all this paleozoic expertise here. I'm just an amateur in comparison. Perhaps CuriousCollector could take a photo of the fat end of the orthocone so that maybe the siphuncle could be studied?

 

14786418037601456850771.jpg

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Alas,... no detail. :( 

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2 minutes ago, Fossildude19 said:

Alas,... no detail. :( 

 

Yes. Too bad. It's otherwise so nicely preserved.

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CuriousCollector

I do no have an HD camera to picture the details that you are probably looking for on the cone base. This it's the best detail i could could capture.

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