Nautiloid camera?

[Peat Burns]

Is this what I think it is?  A camera steinkern of an orthoconic nautiloid?  This is from the middle-Devonian Silica Shale of Paulding, Ohio (although because it is quarry spoil, there is a possibility it could be the underlying Dundee Limestone).  I don't think I've ever found an orthocone in the Silica Shale, let alone one this large.  I hope this is not something that has been intentionally or unintentionally salted in from another site...  That really burns me up.

 

 

 

 

 

[FossilDAWG]

I'd agree with that ID.

 

Don

[Rockwood]

I don't think it is.

The textures just look wrong.

[Tidgy's Dad]

I think it is. 

I believe I can see the trace of the siphuncle right in the centre of the internal photo

 

[Rockwood]

How does anyone explain the skid marks on the other side ?

[Peat Burns]

4 minutes ago, Rockwood said:

How does anyone explain the skid marks on the other side ?

That might be my fault, although I'm not sure.  I cleaned the clay off of it with a brush.  I'll do a test later to see if the brush is hard enough to have caused those.  I have my doubts, but it is a possibility.

[ynot]

I agree that there appears to be a siphuncle on the convex side however I do not see any evidence of a siphuncle on the convex side.

 

 

[abyssunder]

I don't see any siphuncle there.

[Rockwood]

2 minutes ago, abyssunder said:

I don't see any siphuncle there.

The fact that it otherwise appears as if it were a cleaner exposure is the head scratcher.

[ynot]

14 minutes ago, abyssunder said:

I don't see any siphuncle there.

I think that is what Ynot meant.

 

Tony

[Peat Burns]

Thanks all for the thoughts so far. When I get back, I'll examine the posterior end more closely and see if there is anything that might be obscuring the siphuncle.

[Rockwood]

3 minutes ago, ynot said:

I think that is what Ynot meant.

 

Tony

Check on that next time you see him. 

[abyssunder]

10 minutes ago, ynot said:

I think that is what Ynot meant.

or Noty ?
Actually, I can't see the siphuncle opening on any of the sides.

[Rockwood]

5 minutes ago, abyssunder said:

Actually, I can't see the siphuncle opening on any of the sides.

Now that you mention it, there do seem to be multiple spots where one might draw the circle with equal certainty. 

That would say something about that level of certainty.  

[Monica]

Just a wild suggestion, but could it possibly be a rusophycus?

[Peat Burns]

Thanks, @Monica for the suggestion.  In looking at ruscophycus, it seemed a little more morphologically complex than my specimen?

 

I examined the specimen more closely this evening.  I could not identify a siphuncle on the posterior (convex) side.  The anterior (concave) side has a lot of matrix attached to the contact surface which would be difficult to remove to see the siphuncle.

 

The red here shows the contact surface with the septum.  The rest is adhered matrix.

 

 

I also took some close-ups of the surface of the posterior end showing the striations and the area of fracture.  The surface striations were not caused during cleaning with a brush.  This came from quarry spoil, and thus the striations could have been created during transport and spreading of the spoil.  Moreover, the fractured surface rules out some kind of bryozoan-type formation which I thought was a possibility.

 

[Peat Burns]

Perhaps part of the circumference is missing.  If I follow the margins around, perhaps there's enough missing to account for the "missing siphuncle"?

 

[Peat Burns]

For comparison purposes, here is the specimen in question next to a confirmed steinkern of an orthocone (in this case an Ordovician specimen).  Interestingly,  I was unable to locate the siphuncle on the posterior end of many of my Ordovician specimens.  Perhaps it gets worn away?

 

[doushantuo]

this might not clarify things,but..

(paleontology,35/3/free access)

 

[Peat Burns]

2 minutes ago, doushantuo said:

this might not clarify things,but..

Thanks, doushantuo.  I love taphonomy.  Do you have the citation for the source of that figure?

[doushantuo]

I think i gave it ,Peat

[Peat Burns]

2 minutes ago, doushantuo said:

I think i did,Peat

Ok. I found it.

 

Phragmocone implosion in Ordovician nautiloids and the function of siphonal diaphragms and endocones

Publication: Palaeontology

Volume: 35

Part: 3

Publication Date: August 1992

Page(s): 585 – 595

Author(s): David H. Evans

[doushantuo]

notice the lesser mineralization in "A" ,the younger part of the siphuncle in this example:

 

edit:Peat thanks for reminding me that i must check my spelling more often.I "miscited" the name of the publication