Ammonite or regular gastropod?

[Hunterc123]

I hunt fossils in gravel from creeks and the likes. According to the geological survey of similar gravel the age ranges from 200-400 million years ago. I was wondering if you guys could tell me if this was an ammonite or some other sea gastropod. I've found countless other types of fossils but this is the only one like this.

[Fossildude19]

No chambers or sutures showing- I'd go with gastropod. 

[Hunterc123]

4 minutes ago, Fossildude19 said:

No chambers or sutures showing- I'd go with gastropod. 

Would an internal casting of an ammonite show chambers? Fossil 9 in the geological survey I was referring to is what I'm basing my assumptions from. It's said to be an ammonite in the order of goniatites.

[BobWill]

41 minutes ago, Hunterc123 said:

Would an internal casting of an ammonite show chambers? Fossil 9 in the geological survey I was referring to is what I'm basing my assumptions from. It's said to be an ammonite in the order of goniatites.

 

Only an internal duplication fossil would show evidence of chambers since they would have existed on the inside. It could be an external cast of an ammoniod but I agree with Tim mostly because I don't know an ammonoid that evolute (open-coiled), though some may exist.

[Hunterc123]

1 minute ago, BobWill said:

Only an internal duplication fossil would show evidence of chambers since they would have existed on the inside. It could be an external cast of an ammoniod but I agree with Tim mostly because I don't know an ammonoid that evolute (open-coiled), though some may exist.

I'm no expert by any means either. I just know most gastropods I've found have a sort of spire. You can see the edge of this one and its completely flat. It also looked fairly similar to the one in the paper.

[FossilDAWG]

Where are these creeks located?  That might give a clue about the types of fossils that might be expected.

 

Generally I would expect to be able to see some evidence of sutures in an ammonite or goniatite.  However there are modes of preservation where sutures might not be preserved.  

 

Don

[Hunterc123]

9 minutes ago, FossilDAWG said:

Where are these creeks located?  That might give a clue about the types of fossils that might be expected.

 

Generally I would expect to be able to see some evidence of sutures in an ammonite or goniatite.  However there are modes of preservation where sutures might not be preserved.  

 

Don

Here's a link to the post about the geological survey. I'm pretty sure this gravel in the geological survey is the same gravel I'm dealing with.

http://www.thefossilforum.com/index.php?/topic/104015-trilobite-piece-others/&do=findComment&comment=1156177

 

[BobWill]

13 hours ago, FossilDAWG said:

Where are these creeks located?  That might give a clue about the types of fossils that might be expected.

 

Generally I would expect to be able to see some evidence of sutures in an ammonite or goniatite.  However there are modes of preservation where sutures might not be preserved.  

 

Don

Since the vast majority of ammonoids are internal molds that is what you usually expect but I even have some with part of the original shell replaced or duplicated and part of it gone for a direct comparison. I love the ones where the external cast is translucent calcite. You can see the sutures through the outer layer on part of the ammonite and directly on the rest. One heteromorph I found also has part of an internal cast on the same matrix for a display of three of the four possibilities of duplication fossil on one piece!

16 hours ago, Hunterc123 said:

I'm no expert by any means either. I just know most gastropods I've found have a sort of spire. You can see the edge of this one and its completely flat. It also looked fairly similar to the one in the paper.

I can't speak to other ages or sites but many of the gastropods we find in the Pennsylvanian of Texas are planispiral.

[Indagator]

Have u considered a serpulid? I think it is either a serpulid or a gastropod.

[Hunterc123]

2 minutes ago, Indagator said:

Have u considered a serpulid? I think it is either a serpulid or a gastropod.

I can see the resemblance but there's no record of any in this area.

[BobWill]

2 hours ago, Indagator said:

Have u considered a serpulid? I think it is either a serpulid or a gastropod.

That would explain the irregularity and lack of consistent growth of the whorl width.

 

@Hunterc123 I see where the fossil #6 from plate 7 on the page you posted from the old link is actually described as a gastropod. It says "low-spired" but it would have to very low just judging from the image.

[Hunterc123]

1 minute ago, BobWill said:

That would explain the irregularity and lack of consistent growth of the whorl width.

 

@Hunterc123 I see where the fossil #6 from plate 7 on the page you posted from the old link is actually described as a gastropod. It says "low-spired" but it would have to very low just judging from the image.

Fossil number 6 and the ammonite shown in 9 are so similar its just a 50/50 guess which is which. Maybe they know something we don't.