What is this a fossil of ? it is cephalopodan. :smile:

a few more pics.

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

J

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

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?

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

Phil got it! :notworth:
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. :shock:

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

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

J

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. :oops:

Kinda hard for an old desert rat though. :wink: