Jacksboro Texas Mystery

[BobWill]

I have no idea what this could be. I found it at the Lost Creek Dam site in the darker shale on the east end of the slope. It's 11mm long and has a very shiny, dark surface.

 

 

 

 

This end is distorted.

 

 

Other end.

 

[Jonelle]

I don't know anything BUT It almost looks like this in the 3rd pic...maybe these links can help? 

http://pennsylvanianatlas.org/genera/Pseudorthoceras/

 

http://txfossils.com/TxJacksboro.html

[doushantuo]

I seem to see annulations that might suggest "cephalopod fragment",perhaps as Jonelle suggested

[BobWill]

Thanks for posting Rodney's website Jonelle. That is a good resource for Jacksboro fossils that is not well-known. I let him know he needs to separate the bivalves from the brachiopods but he hasn't gotten to that yet.  Rodney wanted to come along Sunday when we went but had family stuff.

 

 Nautiloid was the closest thing I could imagine but we never see them from Jacksboro without sutures showing except on a body chamber and that would not likely show the annulations doushantuo mentioned. This may be an example of preservation of the external surface replaced with something like phosphate. What looks like sutures has way too much folding for a nautiloid and there are no ammonoids that I know of from the Pennsylvanian that aren't coiled. There are also longitudinal ridges barely visible in the second photo near the top center that I've never seen on any of the orthoconic nautiloids we find there so this may be external ornamentation not visible on the usual internal mold.

 

This would be very small for a Pseudorthoceras but could be from the protoconch which I've also never seen. It could also be another genus but I don't know of any that small.

[Jonelle]

@BobWill well you seem to know a lot about it! I honestly just googled the terms and his site was in the top two, so maybe the site is gaining some momentum:) this part looks very interesting to me..do you have any leads on what it could be? They look like little claws ... sorry, I am just a beginner not sure about all of the fossil jargon yet  

 

[BobWill]

Yes Jonelle, those are probably Serpula which are a kind of annelid worm common at that site. There are some papers and a couple of books with information and lots of pictures about Jacksboro but not much online I know about besides Rodney's site. It was assembled fairly recently and includes pages with fossils from other sites. 

[Rockwood]

This strikes me as being something flexible. You don't suppose instead of being sutures they are folds in an egg case similar to what is seen in some condrichthians ?

[BobWill]

Good observation Rockwood. That's something I haven't seen in fossil form. It does seem odd that a the shell would be crushed and distorted that easily and still be preserved with that much detail. Maybe somebody has similar examples of either possibility for comparison.

[Missourian]

The attached 'Serpula' may be the encrusting foram Ammovertella.

[westcoast]

The sutures in pic 2 look like Crinoid ossicle articulations. pic 3 on left looks like pluricolumnal  ..maybe oddly preserved and deformed crinoid...with no central lumen preserved...?

[BobWill]

Thanks for bringing up that possibility westcoast. I'm guessing it has occurred to others too. I had looked at some columns from the site for comparison and found that while articulations were sometimes visible from the outside they were more angular and less extreme than these and of all fossils from there, usually had the worst preservation. I don't know what crinoid stems would look like if the outer ligaments were preserved or if that even happens.  

[BobWill]

I got this reply from someone very knowledgeable about the fauna there.

 

" These hollow chitinous-phosphatic tubes are also found around Lake Bridgeport. I have some that are clearly segmented and some that taper out to a feather or brush-like aperture. The opening is always crushed so I am not sure what the true shape is like. I am hoping they are limb fragments to some unknown crustacean from the late Penn of TX but they will probably turn out to be some kind of worm tube (not as sexy). "

 

Still unknown but some new ideas. I'll be looking for some more of these to try to resolve the mystery.

[TqB]

Interesting - I have a something similar from a Brigantian (Upper Mississippian) UK site in Co. Durham. It's in a bryozoan-rich shale.

The surface is very black and shiny with faint annulations and the meandering shape suggests tube worm.

 

[doushantuo]

Sphenothallus?

edit: which is found in the Namurian of Bear Gulch,BTW

[westcoast]

Good call.

[TqB]

52 minutes ago, doushantuo said:

Sphenothallus?

edit: which is found in the Namurian of Bear Gulch,BTW

 

Intriguing suggestion! I'd only come across Ordovician ones in association with conulariids. There actually are rare conulariids at my UK site, exclusively in nodules.