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Need Help Identifying Species and Age of this Ammonite

AndrewT

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#1
Hello,

My name is Andrew and I'm student taking my first geology class. One of my labs requires us to do research on a rock/fossil that was randomly assigned to us. I have identified mine to be an Ammonite and now my professor would like to know both its age and species. He also would like for me to find information on their orientation when they are fossilized as this one died on its edge. (I have already told my professor about this website and he is perfectly fine with me asking you guys for help.)

I am going to attempt to attach 4 different pictures that I have taken to help in the identification. The fourth picture is a good shot of the septa which it is my understanding should help with the identification. The suture marks are visible in several of the other shots. I have not been able to identify the siphuncle at this point, but perhaps you guys might be able to help me with that.

Thank you,

Andrew



 

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OB

Colossal Squid
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#2
First and foremost, a big hearty :welcome: to our little corner of the web, count 'til 10 and you'll find Kevin or Terry chiming in :smile:
 

Terri

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#4
:welcome: Andrew! Sounds like a fun assignment to me! Is it sliced on the other side? If so a picture of that and another shot of one of the broken ends might be helpful. Kevin (:madsci:) should be along soon...
 

Architeuthoceras

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#5
:welcome:Andrew,

These are both body chamber molds with a little bit of shell preserved. The one has part of the phragmocone attached and it shows a few of the septa, but I don't see any suture lines on either one. Without any kind of locality data it will be real hard to even get started unless someone chimes in who has seen something like this before. I have looked through the treatise and just can't find a match yet :sad: I'll keep looking, do you have any ideas?
 

DWhatley

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#6
Kevin (Andrew you can sort of ignore this as I am less than novice but trying to learn what to observe :grin:) Can you tell me why this would NOT be the same as the one at the bottom of the page here. What I AM seeing similar is that in the top of the curve the sutures do not go to the center in an every other suture pattern. I THINK I see this basic patterning in the second and third pictures.

... and would the below drawing from Indiana G112 Historical Geology handout suggest it is from the Devonian period?

Ammonites
Ammonites are the most common cephalopod group of the Mesozoic. The chambered shells of these squid-like animals had chamber walls that were sometimes intricately folded. The pattern of folds can be used to identify three major groups.
A. Goniatitida (Devonian to Permia) have rounded saddles and pointed lobes.
B. Ceratitida (Carboniferous to Triassic) have rounded saddles and serrated lobes.
C. Ammonitida (Permian to Cretaceous) have folded saddles and lobes.
 

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AndrewT

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#7
Thank you for the warm welcome!

As I had said, this is my first geology class and I kind of dove in head first as this is a senior level course. I am very much still learning. I was under the impression that the suture marks were the ridges on the outside of the shell. Is this not true?

It is sliced and I will post some more pictures of the two pieces together.

Thank you guys again for your help!

Andrew




 

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Architeuthoceras

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#8
I think you two are looking at the ribs and/or the septa. The ribs are on the outside of the shell but show on the internal mold. The septa are on the inside of the phragmocone, they are simple toward the center of the shell and so they look goniatitid. The suture is where the septa meet the shell wall. I'm quite sure this specimen would have a very complex suture line if it were visible.


A generalized sketch of what the sutures would look like (you can't really see them here):heee:
The green is the possible suture line and the blue is edge of the preserved septa.

a WAG here, Androgynoceras, and a mature Macroconch. :hmm:


AndrewT;188639 said:
Thank you for the warm welcome!

As I had said, this is my first geology class and I kind of dove in head first as this is a senior level course. I am very much still learning. I was under the impression that the suture marks were the ridges on the outside of the shell. Is this not true?

It is sliced and I will post some more pictures of the two pieces together.

Thank you guys again for your help!

Andrew
DWhatley;188635 said:
Kevin (Andrew you can sort of ignore this as I am less than novice but trying to learn what to observe :grin:) Can you tell me why this would NOT be the same as the one at the bottom of the page here. What I AM seeing similar is that in the top of the curve the sutures do not go to the center in an every other suture pattern. I THINK I see this basic patterning in the second and third pictures.

... and would the below drawing from Indiana G112 Historical Geology handout suggest it is from the Devonian period?
 

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DWhatley

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#10
I have to do more spacial thinking on this. If you take a cup and fill it with plaster, the plaster is an "internal" mold, right? So are the sutures that show actually an external mold of the part that broke off?:confused:
 

Architeuthoceras

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#11
DWhatley;188643 said:
I have to do more spacial thinking on this. If you take a cup and fill it with plaster, the plaster is an "internal" mold, right?
Right!

DWhatley;188643 said:
So are the sutures that show actually an external mold of the part that broke off?:confused:
No sutures show. The part of the phragmocone that is there is a replacement of the shell.
 

DWhatley

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#12
but is it the shell from the INSIDE or the Outside? If it is from the inside then the actual structure has chamber like bump that point IN rather than telling anything about the viewable out side. If it is shell from the attached outer shell of the swirl, then it represents bumps that would have been visible and mirror the outer part of the mold. :confused: still
 

Solius

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#13
Sorry, I can't help with the ID, but... wow! When I had invert paleo, years ago, we IDed most of the major phyla down to class, and that was it. Even after all these years, if I get the genus or family, I am a happy camper. Good luck.
 

Architeuthoceras

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#14
DWhatley;188663 said:
but is it the shell from the INSIDE or the Outside? If it is from the inside then the actual structure has chamber like bump that point IN rather than telling anything about the viewable out side. If it is shell from the attached outer shell of the swirl, then it represents bumps that would have been visible and mirror the outer part of the mold. :confused: still


The septa and part of the outer shell are replaced (? possibly original shell) just at the inside radius of the body chamber so both the inside and outside are preserved. The body chamber was open to the sea and was filled with mud, the phragmocone was closed off to the sea and remained hollow (gas filled ?). There may have been more of the phragmocone preserved, but it would have been very delicate and broken away very easily, all that is left is the parts you can see. The suture line would be where the septa attach to the inside of the shell which would be the inside radius of the outer shell. :talker:
 

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AndrewT

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#16
Hey guys,

Sorry it has been awhile. I had tests in both my quantum physics class as well as my chemistry class to keep me busy.

Since last posting, I spoke with my professor about what you said, Kevin. He told me that you are right, the suture marks are not visible and so the species cannot be determined. He said that the genus should be able to be determined though.

Also, I still need help finding any research on their orientation when they die or are deposited in the sediment. This sample died on its edge. Another question that was asked, is what happened to the other half of the shell?

Thank you again so much for your help!

Andrew
 

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