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Wrangellian

I've received a couple nice Upper Ordovician additions to my collection courtesy of @JUAN EMMANUEL and I'm finally posting them now... (Thanks Juan!)

 

First, is this Tentaculites or Cornulites? I wish I could get better pics.

Manitoulin Fm, Hamilton, ON.

5bf5255acb9be_CornulitesorTentaculites.thumb.jpg.6567819c2214045072186630def00a07.jpg

5bf52615879e7_CornulitesorTent(2).thumb.jpg.b7661fbff470cb1a618df46b45466683.jpg

 

 

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Wrangellian

Second: We have the ID for this orthocone, Treptoceras sp., Georgian Bay Fm of Toronto. I'd like to know to to what extent we are seeing external ornamentation and what extent is exposed internal features (eg. septa from a partially crushed/collapsed shell), and what are those 'knobs' on the smaller specimen and toward the narrow end of the larger? Anyone have any ideas?

 

5bf5268ee1958_Treptocerasa.thumb.jpg.65e23fb971bde5ab472227d7b6ad2db8.jpg

5bf52699bb083_Treptocerasdet1.thumb.jpg.8e4ffdda243e7cfce8f201774e077ff7.jpg

5bf5269ed4491_Treptocerasdet2.thumb.jpg.4d3ea92a737e10ec59491c2e63df56ec.jpg

 

Reverse side with snails and apparently large ichno trails:

5bf526934c116_Treptocerasback.thumb.jpg.d0bb89c383c59221187d33af1e52ca4d.jpg

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Rockwood

I think the profile is more consistent with  Tentaculites on the first one.

I think the knobby look is external, and the smooth internal/intermediate for the cone.

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Rockwood

After a little study I may have to reverse direction on the first one. They do have the look of a shaving from a metal lathe. That would be cornulites. 

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Tidgy's Dad

Cornulites.

The internal structure of Treptoceras looks like this :

 Image result for treptoceras(from "Cincinnatian Fossils and Stratigraphy."

What you have there is an internal mold of the outer shell showing the chambers. 

And the bumps at the base do show on well preserved specimens, it's some sort of ornamentation. 

Image result for treptocerasRobert C. Frey "Journal of Palaeontology". Vol.63, No. 5, (Sep., 1989), pp.604-620. 

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minnbuckeye

Could the knobs be encrusted bryozoans?? From the Drydredgers:

 

Many Cephalopods were encrusted with the bryozoan, Spatiopora, which shows aligned monticules.This suggests the Cephalopods' shells were encrusted with these bryozoans while they were swimming.
P1011318.jpg spatio1.jpg spatio2.jpg

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Northern Sharks

As far as I'm aware, we only have Devonian Tentaculites here in Ontario. In my opinion, those are Cornulites. I can't speak for the GB formation, but they were a rare find from the Verulam. I only ever found 2 over all the years I collected that particular formation.

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Wrangellian

Thanks everyone for the info and ideas. My pics aren't good enough to show it but on close examination I'm sure I'm looking at shell material on the Treptoceras. (I don't see any bryozoan encrustation.) It looks as if the knobs kind of turn into ribs toward the mature end of the shell, though some of them may have been abraded off (either before deposition or after erosion). The thick shell is evident especially at the open end of the smaller specimen. If I didn't think it would be a waste of time I'd try to get more pics.

 

I see by Sepkoski that Tentaculitids extend from the Ordovician to the Devonian, and Tentaculites is the only genus in the Ordo (from the Tremadocian on up thru the Devonian). But I'll take y'all's word for it that this is Cornulites, and I'm happy about that! (Aside: Sepkoski lists Tentaculitids within the Molluca, while the Cornulitids are under 'Problematica'. To me they look close enough that they should be in the same group, whatever that might be, or is this a case of convergent evolution?)

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