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ober

collignociceras?

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ober

Hello all. Time for me to go to school again, and ask for help identifying this fragment of what I take to be an ammonite. I found it in Mancos Shale outside of Moab. This segment is about 10cm long and about 4.5cm wide. It is in a thin slab with no sign of the shell continuing on the underside of this piece of stone. The two photos show all that can be seen and the third gives a sense of the thickness of the rock. I was unsure of what this was until PFOOLEY called my attention to Kennedy et al. A Revision of the Turonian Members of the Ammonite subfamily Collignonceratinae. This helped me see I was looking at an ammonite. In fact, this looks to me fairly close to Kennedy’s fig 32 on page 39, for anyone who has this source. The spine has distinct bumps at the shell ridges and the ridges themselves are sharp and more widely spread. In his terms, I’d guess this is a robust rather than gracile structure. I do not think it is Prionocyclus since its spine, as pictured in Kennedy, seem to be smoother along the entire back. When I look on line at other families I see some went extinct earlier than the Cretaceous and some have clearly smoother shells. I don’t know the complete universe of ammonites that inhabited this area in the Cretaceous so don’t know who the other contenders might be. The two families I see are Collignoniceratidae and Prionocyclus. If I am close that it is in the Col. family, I don’t think it looks like c. jorgensen or c. praecox. It looks like c.woolari. After all this, my questions. Is this enough of a segment to make a reasonable identification? Is this Collignonceras? If not, what am I missing (seeing or not seeing)? As always, thanks for your help.

5646ED11-906B-47B4-AB2F-08B7553DDF3C.jpeg

1D1AC23C-F3C9-4D59-9EBA-F334B178B34A.jpeg

94B54DBB-BAA4-4678-8F04-10C553CB84A4.jpeg

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Innocentx

I can't help, but that's a nice find. Hope you can get clarification.

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ynot

Not much there to go on, but maybe @PFOOLEY can help.

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PFOOLEY
21 hours ago, ober said:

It looks like c.woolari.

Yes it does. :) 

 

Aside from ornament, understanding the geology (members of the Mancos) from where the specimens were collected is extremely helpful in identification of Collignoniceratids. For example, Collignoniceras woollgari is stratigraphically lower than Prionocyclus Hyatti.

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ober

Mike, thank you. The Kennedy piece is very helpful, as is knowing now this is a lower strata than Prionocyclus. That will help with other things I’ve found in this layer. Tom

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PFOOLEY

You are welcome.

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