Mancos Shale Ammonite: Help Wanted!

[DeepTimeIsotopes]

I've been looking for an ID for this big boy.

So far I've found this site (http://www.ammonoid.com/Prionocyclus.htm) but I'm not sure what I'm looking for to differentiate between them. Could anybody more knowledgeable help me out?

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[Heteromorph]

Nice find! The tubercles are pretty extreme. It does look Prionocyclus to me, but @PFOOLEY would be the one to help you with a species level identification. 

[DeepTimeIsotopes]

42 minutes ago, Heteromorph said:

Nice find! The tubercles are pretty extreme. It does look Prionocyclus to me, but @PFOOLEY would be the one to help you with a species level identification. 

At least I'm on the right track.

[Heteromorph]

39 minutes ago, UtahFossilHunter said:

At least I'm on the right track.

Do you have pictures of the specimen with measurements next to it and some specific information on it’s dimensions? I can tell it is a pretty big specimen, but specifics always help. 

[PFOOLEY]

Great ammonite, @UtahFossilHunter! For an accurate i.d., preparation and/or member of Mancos is needed. The Mancos Shale is huge in terms of geologic time scale, spanning the Turonian, Coniacian and Santonian! In the Middle Turonian, Collignoniceras  is evolving into Prionocyclus  and the two genera can often look way too similar at different points in their ontogeny. You definitely have a Collignoniceratid, but more information is need to narrow down genus and species. 

 

Note: pay attention to the Inoceramids as well when in the field...they can be quite useful as they have a zonage similar to that of Ammonites (W.I.S.).

 

For reference:

A REVISION OF THE TURONIAN MEMBERS OF THE AMMONITE SUBFAMILY COLLIGNONICERATINAE FROM THE UNITED STATES WESTERN INTERIOR AND GULF COAST

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8 hours ago, Heteromorph said:

Do you have pictures of the specimen with measurements next to it and some specific information on it’s dimensions? I can tell it is a pretty big specimen, but specifics always help. 

I can get the measurements later today. 

14 minutes ago, PFOOLEY said:

Great ammonite, @UtahFossilHunter! For an accurate i.d. preparation or member of Mancos is needed. The Mancos Shale is huge in terms of geologic time scale, spanning the Turonian, Coniacian and Santonian! In the Middle Turonian, Collignoniceras  is evolving into Prionocyclus  and the two genera can often look way too similar at different points in their ontogeny. You definitely have a Collignoniceratid, but more information is need to narrow down genus and species. 

 

Note: pay attention to the Inoceramids as well when in the field...they can be quite useful as they have a zonage similar to that of Ammonites (W.I.S.).

 

For reference:

A REVISION OF THE TURONIAN MEMBERS OF THE AMMONITE SUBFAMILY COLLIGNONICERATINAE FROM THE UNITED STATES WESTERN INTERIOR AND GULF COAST

I will post the member later today when I can get access to my notes. If my memory serves, it was the upper member but that could totally be wrong. I also have others from the layer right above that may help constrain the age. 

Thanks for the reference!

[PFOOLEY]

5 minutes ago, UtahFossilHunter said:

Thanks for the reference!

You are welcome.

6 minutes ago, UtahFossilHunter said:

I also have others...

[DeepTimeIsotopes]

4 hours ago, PFOOLEY said:

You are welcome.

I got my notes, it is from the Blue Gate Member.

[PFOOLEY]

1 hour ago, UtahFossilHunter said:

I got my notes, it is from the Blue Gate Member.

If its that young, you may want to compare with Forresteria for the genus. I think F. hobsoni is an index (marker) fossil. 

 

Go find more.

 

[DeepTimeIsotopes]

1 hour ago, PFOOLEY said:

If its that young, you may want to compare with Forresteria for the genus. I think F. hobsoni is an index (marker) fossil. 

 

Go find more.

 

Thanks, I will post pictures once it's cleaned. 

And I will certainly look for more!

[DeepTimeIsotopes]

On 11/15/2018 at 11:02 PM, Heteromorph said:

Do you have pictures of the specimen with measurements next to it and some specific information on it’s dimensions? I can tell it is a pretty big specimen, but specifics always help. 

Late as usual but here's the measurements

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