Pennsylvanian Nautiloid From Jacksboro Texas

[BobWill]

I found this nautiloid in the Graham Formation at the Lost Creek site near Jacksboro Texas. The grid is 5x5mm. Picture taken with my new "pluggable" digital microscope I got from Amazon for $35! Any ideas?

One more close-up

Edited July 24, 2015 by BobWill

[Rockwood]

I can't help ID it, but it looks like you have some excellent science in early ontology going there.

[Guguita2104]

Great !I'm not certainly, but it seems a heteromorf ammonite...I can't be more precise, sorry.I speculated that because I read an article about Graham Formation that say we can found Cretaceous fossils ( and heteromorf ammonites lived only in this period).

[BobWill]

Maybe there's another formation with that name in the Mesozoic somewhere Guguita, but this is Pennsylvanian so that rules out heteromorph. The detached piece is crushed at the small end but from the groove inside the large piece I assume a more complete specimen would show it to be planispiral with evolute coiling. Just the closely-spaced growth lines but no sutures or ribs are visible and the whorl section is very slightly depressed laterally and with somewhat angular curves on all 4 margins. There are also shallow depressions on the ventral side of the ventral margins.

Edited July 24, 2015 by BobWill

[Guguita2104]

Sorry for the mistake ,Bob...Try to see this site and compare with some Domatoceras images:http://www.westernpaleo.org/pdf_files/fossil%20identification-1.pdf. It's the best I can do

Edited July 24, 2015 by Guguita2104

[BobWill]

Thanks Guguita, I think you're on the right track. We find Domatoceras obsoletum here but they have much flatter sides so this may be another species to add to the faunal list. I couldn't make that link work, I'll try again later.

Edited July 24, 2015 by BobWill

[abyssunder]

Probably,Guguita refers to this link http://www.westernpaleo.org/pdf_files/fossil%20identification-1.pdf
Also I found something,but I don`t know if it`s correctly determined as Domatoceras sculptile.Probably refers to Grypoceras(Domatoceras) sculptile (Girty,1911). http://northtexasfossils.com/nautiloids.htm

Edited July 24, 2015 by abyssunder

[BobWill]

Thanks Abyssunder. I should have looked at Lance's site first. This looks nothing like the Domatoceras I display which has a 40mm whorl width compared to the 7mm on this one and a wavey ventral margin not seen on this so I failed to make the connection.

[howard_l]

Do you think the area I circled in your picture is the Siphuncle?

[BobWill]

Definitely the siphuncle. It's visible in the same location on some other samples I found.

[howard_l]

I will try to look at my source material I have on the Pennsylvanian but unfortunately they are in my office and I won't be there until Monday.

[howard_l]

I looked through my sources and my Treatise (Mollusca part K), The picture showing the siphuncle shows a rectangular shaped shell and the siphuncle is toward the ventral from the center. I found a couple of ideas. One questions, is there any nodes anywhere on the shell, I can't tell from the pictures. If there is, it probably Metacoceras. If it doesn't have any nodes, it also has the same shell morphology as Thrincoceras Which is very common in the Mississippian of Kentucky but continues to the Permian. I have never seen it in this Country except for the Mississippian. I would say it is in either the family Tainoceraidae or Trigonoceratidae.

[Herb]

I looked through my sources and my Treatise (Mollusca part K), The picture showing the siphuncle shows a rectangular shaped shell and the siphuncle is toward the ventral from the center. I found a couple of ideas. One questions, is there any nodes anywhere on the shell, I can't tell from the pictures. If there is, it probably Metacoceras. If it doesn't have any nodes, it also has the same shell morphology as Thrincoceras Which is very common in the Mississippian of Kentucky but continues to the Permian. I have never seen it in this Country except for the Mississippian. I would say it is in either the family Tainoceraidae or Trigonoceratidae.

I think Howard is on the right track with his id,s