Ammonite?

[p0edwards]

I found this while fossil hunting for the first time. I’m curious if anyone can identify it. I found it on the side of a road in Lee Summit Missouri, Pennsylvania aged rock I believe.

[Tidgy's Dad]

Nice find!

What is the size, please?

If it is Pennsylvanian, it will be a goniatite or nautiloid.

[p0edwards]

2 hours ago, Tidgy's Dad said:

Nice find!

What is the size, please?

If it is Pennsylvanian, it will be a goniatite or nautiloid.

Sorry for the late response, it’s about 4 cm across at the widest point roughly 3 cm tall

[Jaybot]

Incredible find, especially for your first hunt!  I have yet to find one of those.

It might be a goniatite

[p0edwards]

3 minutes ago, Jaybot said:

Incredible find, especially for your first hunt!  I have yet to find one of those.

It might be a goniatite

Thank you! It was very exciting. My only concern with it being a goniatite is the inside sections (not sure the term) aren’t wavy lines like the pictures of goniatites I’m seeing online

[Ludwigia]

I would suggest that this is rather a spiralform nautiloid. Maybe someone here familiar with the Formation could suggest an id. Nice specimen!

[Bullsnake]

@Missourian

[p0edwards]

2 hours ago, Ludwigia said:

I would suggest that this is rather a spiralform nautiloid. Maybe someone here familiar with the Formation could suggest an id. Nice specimen!

After looking up a few images online I can see a hefty resemblance, I think this is pretty accurate but definitely would love confirmation from someone else!

[Jaybot]

I'm not too experienced with id'ing nautiloids, but here is a good site for reference that I use:   https://pennsylvanianatlas.org/

[FossilDAWG]

The "wavy lines" are suture lines, formed where the septa (the internal parts of shell that divide the interior into chambers, called camerae) joins the exterior part of the shell.  If you remove the exterior, you see the septa exposed as suture lines.  The septa may be flat or gently curved, as in nautiloids, so the suture lines are straight or almost so.  In goniatites and ammonites, the septa project forward or backwards, and may be very complicated, making for more complex suture lines.  However, these projections and complicated structures are formed where the septa join the outer shell, to act as butresses to strengthen the shell.  As you go deeper into the shell (as happens when the shell is worn, or ground down and polished) the complicated structures are removed, and the remaining part of the septa are more and more simply curved.  If you look at an ammonite that is cut and polished precisely down the middle, the septa are smooth curves that look just like nautiloid septa. 

 

Regarding the remarkable fossil @p0edwards posted, you can't tell what the suture lines would have looked like because the section is almost perfectly in the middle.  However, you can see the siphuncle, the tube that runs back through the camerae.  In this case it is pretty much in the center of the septa, which indicates a nautiloid.  Goniatites and ammonites have the siphuncle right against the ventral (outside) edge.

 

Don

[p0edwards]

12 minutes ago, FossilDAWG said:

The "wavy lines" are suture lines, formed where the septa (the internal parts of shell that divide the interior into chambers, called camerae) joins the exterior part of the shell.  If you remove the exterior, you see the septa exposed as suture lines.  The septa may be flat or gently curved, as in nautiloids, so the suture lines are straight or almost so.  In goniatites and ammonites, the septa project forward or backwards, and may be very complicated, making for more complex suture lines.  However, these projections and complicated structures are formed where the septa join the outer shell, to act as butresses to strengthen the shell.  As you go deeper into the shell (as happens when the shell is worn, or ground down and polished) the complicated structures are removed, and the remaining part of the septa are more and more simply curved.  If you look at an ammonite that is cut and polished precisely down the middle, the septa are smooth curves that look just like nautiloid septa. 

 

Regarding the remarkable fossil @p0edwards posted, you can't tell what the suture lines would have looked like because the section is almost perfectly in the middle.  However, you can see the siphuncle, the tube that runs back through the camerae.  In this case it is pretty much in the center of the septa, which indicates a nautiloid.  Goniatites and ammonites have the siphuncle right against the ventral (outside) edge.

 

Don

This is amazing information thank you so much! I will definitely do more research on this and now I have a great start!

[jpc]

Great find , esp for a first time out.  

(Doesn't Lee's Summit have an apostrophe s?)

 

[Missourian]

Gorgeous nautiloid that needs no trimming or prep of any kind.

 

Having been found in Lee's Summit, it likely is from the Winterset Limestone. Metacoceras and Liroceras tend to be the most commonly found coiled cephalopods in area limestones, while ammonoids are very rare. I'd guess Liroceras based on the size and tight structure.