Ammonoid Or Gastropod?

[Jeffrey P]

Found this specimen on Sunday at Soule Road Quarry in Pierceville, NY, in Madison County. Not sure if it's an ammonoid (goniatite) or a gastropod (Platystoma). It was found in the Upper Ludlowville Formation, It is Middle Devonian. Please share your ideas. Thank you.

Edited November 4, 2014 by Jeffrey P

[Ludwigia]

The photo's slightly fuzzy, but I'll go with gastropod.

[Rockwood]

Second that. There seems to be shell left near the apex with no sign of septa or suture.

[Fossildude19]

Nice one, Jeff.

I think it's a gastropod as well.

Regards,

[Jeffrey P]

Thanks guys. I was leaning in the same direction. This is the first Platystoma gastropod I've found in Madison County. The species list continues to grow.

[Shamalama]

The key feature is that the spiral "rises" from the center of the shell. In Gonaitites and ammonoids the spiral is imbricated so that the younger sections overlap the older. Of course this does not apply to heteromorphs.

[erose]

That's the kind of fossil that often requires a few more specimens from the same site to get a better handle on the ID. Even partials can have diagnostic features and it may take a handful to get a feel for the entire creature. But I do agree it seems much closer to gastropod in nature.

Edited November 4, 2014 by erose

[tmaier]

A peek at the backside would be very informative.