Guess What? Thing 2

[Architeuthoceras]

What is this a fossil of ? it is cephalopodan.

 

[Architeuthoceras]

a few more pics.

 

[Jean]

no idea....but in that last shot it looks like a ginormous statolith!

J

 

[Tintenfisch]

Or eye lens... but 11cm would be huge, plus the lenses aren't concave on the inner surface...

 

[Phil]

Looks more like bone to me, but I'm sure it's not! It's not a huge ammonoid spine base or something like that?

 

[cuttlegirl]

My only thought is that it is a really big protoconch... or maybe an aptychus. Once again, just wildly guessing.

 

[Architeuthoceras]

Phil got it!

spine base or something like that?

I think, basically just guessing, that it is a node (can't really call it a spine) on the shell of a coiled nautiloid. It is from the Mississippian Chainman Shale where I find a few small coiled nautiloids. This is the thickest piece of shell I have ever found though. Below are a few pics of some of the small nautiloids showing the nodes running along the flank close to the umbilical shoulder. Doing a few calculations on the ratio of diameter/shell thickness of the smaller ones I come up with a diameter of between 450mm and 1050mm (probably closer to the upper figure, shell thickness was greater on the venter where I had to measure some than on the flanks where the nodes are), making it a pretty big shell.

 

[Architeuthoceras]

a few more, and a closeup of something growing on the shell, probably a bryozoan

 

[Jean]

I agree about the bryos they look very like ones we get over here growing on shells, rock, seaweed.........etc!

J

 

[Architeuthoceras]

Thanks Jean, I guess I really should go and take a good look at the ocean one of these days and see just how some of the things I find as fossils actually live, and how they look alive.

Kinda hard for an old desert rat though.