What The Heck Is This? It's A Devonian Ammonoid!

[hitekmastr]

I was checking out a new Devonian spot and came across a section that contained a lot of deepwater marine species - cephalopods, very large clam internals, orthonoceras, etc. Didn't have much time at the site but I was scanning some large boulders and concretions up to 3 or 4 feet long and spotted this gem sitting on a boulder.

It has nautiloid features but I'm not familiar with this fossil category so any observations or opinions will be much appreciated. This fossil is 14 centimeters long. As you can see this is a very distinctive and unusual fossil and it has just become one of my favorite Devonian finds since we started fossil collecting. This is the photo I snapped at the site today - I'll post a better image tomorrow.

(see more pictures on Page 2 of this thread)

I'm thinking maybe Cephalopod Goniatites (a Middle Devonian Nautiloid)?

UPDATE! - 13.Sept.2013 - The consensus is that this is an ammonoid known as Agoniatites vanuxemi, which existed between 385.3 and 392 million years ago. It thought to be the only species of Agoniatites found in the Mahantango Formation. It is also rare to find this fossil in Pennsylvania.

Edited September 13, 2013 by hitekmastr

[BobWill]

Looks like half a nautiloid. Go back and get the rest:)

[Fossildude19]

Wow!

Nice nautiloid, Michael.

Possibly Agoniatites, or Manticoceras?

I agree - go back and find the rest of it!

Regards,

Edited September 7, 2013 by Fossildude19

[Herb]

Very nice, I hope you can find all of it.

[hitekmastr]

I found this at the very end of the day, sun going down - looked up and it was sitting on a large boulder at the bottom of a cascade of boulders. The rest of it could be anywhere in the pile - I checked to see if the rest of it was nearby but no luck. Maybe a more thorough search will turn up something. It also may be that the other portions were crushed by the boulders. Only had a short time at this particular spot which we hadn't explored before so hopefully more deepwater Devonian finds to come from this location...

[BobWill]

Ha Ha! I was kidding about finding the rest. It's just as likely to be worn as broken, but you never know. The flat surface may be good for displaying it standing up

[Bullsnake]

That is really cool looking. Looks very fragile, too.

It kind of looks like a (caricature) snake head!

[hitekmastr]

Actually, the rippled segments are very hard rock and not at all fragile, however, the circle of small pieces surrounding the very center are fragile and some broke apart which means I have to put them back together - some puzzle work for me.

The cascade of rocks where I found this is quite steep with very large boulders overhead - posing a rockslide hazard. It is most likely that the rest of this piece was buried or broken. However, there is a reasonable chance it still exists because of the clean break that shows in the fossil. When Nan and I revisit the spot we'll look for the other half of this piece, and anything else that may be interesting given that this is appears to be a site with deeper water species and larger species as well.

[Ludwigia]

I beg to differ, if I may. I believe that hitekmastr was right on his first guess with Goniatites, which belong to the sub class of the Ammonoidea. I don't think it's a Nautilus because of the type of curvature of the lobal lines with the typical pronounced meandering curve which is visible at the bottom near the keel. Nautiloid lobal curves are generally simply concave/convex.

[the tatter]

(It kind of looks like a (caricature) snake head!)

Yes, I can see the snake head!!!

[xonenine]

it does seem to resemble most a species of Manticoceras, an ammonoid...very nice

Edited September 8, 2013 by xonenine

[Shamalama]

Nice find!

[BobWill]

Well spotted Lugwigia. I didn't notice that saddle on the ventral margin but I don't think it's Manticoceras as xonenine suggested for two reasons. First, the major suture feature is a lobe instead of a saddle as on a Manticoceras. Also there is no lobe near the umbilical margin as seen on the drawings. I'm good with it being an ammonoid but I'm looking for a better candidate.

Edited September 9, 2013 by BobWill

[Ludwigia]

saddle on the ventral margin......suture.......lobe.......umbilical

Nice to see these terms in English all together in black and white. I learned all my fossilology in German, so the English terms get lost in the translation sometimes.

[GerryK]

What you have is a very rare Agoniaties. Take special care of the specimen and make sure it has as much locality and stratigraphic information as possible. I have collected Agoniatites from New York and know it occurs from three different horizons. From the Cherry Valley Limestone Agoniatites vanuxemi is common. In the Ludlowville Formation a rare Agoniatites unilobatus occurs. From the Moscow Formation in the Windom Member at Penn Dixie Quarry another rare Agoniatites sp.has been found. To have an Agoniaties from Pennsylvania is a very special specimen and hopefully some day it will be deposited in a research institution

[Auspex]

wow.....

Congratulations!

[piranha]

...To have an Agoniaties from Pennsylvania is a very special specimen and hopefully some day it will be deposited in a research institution.

I'm wondering if it was actually found in New York?

[lissa318]

Wow that's wonderful!!!!! Congrats!!!

[BobWill]

Looking back I notice that Agoniatites is one of the suggestions Tim made way back in post #3. That'll teach me to look up pictures when someone with experience offers ideas. It would be great to see an edge view of this one to get a better idea of what the venter looks like.

[Reconquistador]

I agree with GerryK. This is certainly not goniatid, but it is agoniatid, according to the suture on ventral side.

[hitekmastr]

Of course, I'm totally delighted if this is in fact an Agoniatite...since one of our goals is to find rare fossils that add to the fossil record. This was definitely found in Pennsylvania, about an hour from our home - at a fossil site near Deer Lake where there are a lot of very deepwater fossils (large clams and other deep water fauna).

Online sources describe Agoniatites as a genus of primitive "nektonic" (nektonic means free swimming) carnivorous shelled ammonoids from the order Agoniatitida family (Agoniatitidae). They thrived during the Eifelian and Givetian ages (Middle Devonian) - approximately 385.3 to 397.5 million years ago. I believe the site where I found this is about 385 million years old.

I'm not sure of the geostrata but I believe it was lower strata (not upper levels) - lower (deeper) formations. I did return and try to find the "other half" however no luck. It is probably buried in a large pile of large rock rubble. Here are some additional photos of the fossil Note that the small "center ring" (see original image in my first post) broke into pieces during transport and I am piecing it together:

Edited September 12, 2013 by hitekmastr

[rejd]

That is such a great looking piece. Congrats on the rare find. I myself am hoping to someday find something rare that may one day end up in a museum. Make sure to keep us updated on the progress of this piece. Are your plans to keep it or donate it?

[hitekmastr]

That is such a great looking piece. Congrats on the rare find. I myself am hoping to someday find something rare that may one day end up in a museum. Make sure to keep us updated on the progress of this piece. Are your plans to keep it or donate it?

Not sure if and when I would donate it, or to which institution - don't even know who would be interested in having it and studying it.

[hitekmastr]

Here are some photos of additional fossils I collected during the same trip, at the same rock formation which is near Deer Lake in the Hamilton Group/Mahantango Formation - some of the rocks are different colored from the Agoniatid ammonoid fossil I found.

These are all from the same large group of rocks which included many different colors - the rocks are extremely large and include some concretions that are up to 3-4 feet long, which provides a rare opportunity to find deeper marine species and larger fossils as well.

A Large (4.5 cm) Brachiopod - Identified as Spinocyrtia granulose

This is the largest brachiopod I've seen/collected

Two Cephalopods - Pieces and a "Cap"

A Small Well Articulated Gastropod

I also found the largest Devonian clams we've seen since we started exploring Devonian formations, which is one reason why I thought this was a deepwater site when it was "live."

Edited September 12, 2013 by hitekmastr

[hitekmastr]

These are some additional fossils I found and left at the site:

(note the size of the large white cephalopod section - the original ceph must be really large)