Widder Fm.: This is not Tornoceras

[Shamalama]

I came home this afternoon in some ridiculously warm weather for January (50F, 10C) and happened to look at a rock I'd collected from the Widder formation about two or three years ago that I had sitting out weathering. It was one that @Kane had quarried from his Gonaitite perch out of the Widder formation and kicked down to me. I'd originally kept the rock because it had a bunch of Mucrospirifer thedfordensis in it and I wanted to see what else would erode out of it. When I turned the rock over I spotted a small round fossil that was brownish... a different color than most fossils.

 

 

It was pyritized so I chipped it out of the rock and took a look at it. It was a Gonaitite and one that I had never seen before!  Most Gonaitites that I have found at Arkona are from the Arkona formation and fall into the Tornoceras arkonense genus, but this one is different.

 

Tornoceras arkonense above, mystery Gonaitite below.

 

I used a new tool that I recently purchased, a home tattoo pen, to clean out one side of it. The pen is quite effective on softer shale or limestone as long as the fossil is much harder. In this case it was pyritized so I didn't have to worry about damaging the fossil. 

 

It turns out that this specimen has a smaller diameter phragmocone than Tornoceras arkonense  as there are prominent ridges (rather than gaps as in T. arkonense) along the sutures. The suture pattern is plain with a sweeping parabola facing backwards, a straightish line across the keel and then another parabola.

 

I've looked into the usual sources ("CHECK LIST OF FOSSIL INVERTEBRATES DESCRIBED FROM THE MIDDLE DEVONIAN ROCKS OF THE THEDFORD-ARKONA REGION OF SOUTHWESTERN ONTARIO", Stumm and Wright, Paleontology of New York, Hall) and don't see much that correlates to what I've found.  Anyone have an idea?  The fossil itself is 7/16" (11mm) at it's widest and 2/16" (4mm) thick. It comes from the Middle Devonian aged (Givetian stage) Widder formation at Hungry Hollow, Ontario, Canada.

 

Thanks for looking!

[Jeffrey P]

Wow Dave! I can't help you with the ID on that goniatite, but it sure is a swell find! Congratulations. I am curious what the ID would be. 

[RuMert]

If I found that Tornoceras arkonense  I'd think it's a nautilus

[FossilDAWG]

Dave, can you see suture lines?  Are you completely confident that it is a cephalopod and not a planispiral gastropod?

 

Don

[Shamalama]

20 hours ago, FossilDAWG said:

Dave, can you see suture lines?  Are you completely confident that it is a cephalopod and not a planispiral gastropod?

 

Don

Well, now that you point it out.... I hope I didn't make a noob mistake.  The last pic and second to last pics show the "sutures" the best. The fact that the "sutures" arc backwards makes me think Gonaitite as all the gastropods seem to have linear growth lines perpendicular to the shell growth.   I checked all my literature again and no planispiral gastropods fit the bill. Straporallus sp. would be the closest but that does not have the backwards arc for a growth line.

 

If you have any suggestions for alternate ID please let me know.

[Shamalama]

20 hours ago, RuMert said:

If I found that Tornoceras arkonense  I'd think it's a nautilus

Yes, they do look a little like nautilus.

[Natalie81]

@Manticocerasman 

[Shamalama]

Ok, I posted these same pics over in Facebook on the "Fossils of Arkona, Ontario" group and it has been suggested that it's an immature Agoniatites vanuxemi Goniatite.  Apparently a few others have been found, as noted by Mike Topor and Matt Devereux on Facebook, but not studied extensively. A paper by Eric C. Prosh in 1990 describes it as:

 

"Shell small, discoidal; three whorls preserved, maximum
diameter (D) 14 mm. Umbilicus imperforate, constitutes about
113 of total shell diameter (U = 4.5 mm), only moderately
deep. Protoconch approximately 1 mm wide. Lateral profile
moderately well inflated; at whorl 3 the ratio of whorl width
(W, = 6 mm) to whorl height (H, = 6 mm) equals 1. Dorsal
imprint zone well developed, moderately deep, impressed 116
of H, at whorl 3.
Ribbing pronounced in early whorls, coarse, about one rib
per millimetre at whorl 2, becoming finer and more crowded
adorally, spaced every 112 mm by whorl 3. Shallow, but
prominent, ventrolateral furrows extend the full preserved shell
length, but unlike the ribbing, display no adoral weakening.
Suture indistinct, best preserved ventrally, where it displays a
shallow, though somewhat broad, ventral lobe and an asymmetrical
ventrolateral saddle."

 

https://www.researchgate.net/publication/237173925_The_Devonian_ammonoid_Agoniatites_from_Hungry_Hollow_southwestern_Ontario?fbclid=IwAR0Obqq9HJg42e_0J8wcCaP26LKdox9uiY0aaGO0LU4W-ex5gMeKkIFvO7Q

[FossilDAWG]

How cool would that be!

 

Don

[Shamalama]

13 hours ago, FossilDAWG said:

How cool would that be!

 

Don

Frosty