Oyster, cephalopod, or what?

[Sagebrush Steve]

I am at the Santa Rosa Gem and Mineral show and one of the vendors had this on display, labeled as an oyster.  I’m not sure that’s correct and the lady said it could also be a cephalopod.  Looks to me like a loosely coiled ammonite, what does everyone think?

 

[Sagebrush Steve]

Another photo.

[paleoflor]

Looks like a heteromorphic ammonite, to me (but I am by no means an expert on the beasties).

[Kane]

Looks like a heteromorph ammonite to me. 

[Darktooth]

A heteromorph ammonite perhaps.

[Darktooth]

Well there's a good chance all 3 of us can't be wrong?!

[Darktooth]

For $25 I would buy it regardless of what it is. It has the "cool" factor.

[Sagebrush Steve]

32 minutes ago, Darktooth said:

For $25 I would buy it regardless of what it is. It has the "cool" factor.

I thought about it but passed, though I may go back.  Looks like it is mostly an internal mold, although you can see some shell in the first photo.  I forgot to bring a loupe and my eyes aren’t as good as they once were.

[FossilDAWG]

It is a Nostoceras madagascarensis, a heteromorph ammonite.  However it looks as if the whorls in the turret part may be largely carved.  Hard to be sure from a photo though. 

 

Don

[Carl]

I'm with @FossilDAWG completely.