Hi Ob. I think the dendrites are just the usual - post-depositional pyrolusite (manganese dioxide). There's a baby skate in the top right hand corner with pyrolusite dendrites in the position of its eyes.
Here attached is a sketch showing the position of the ink sac (I want to write "sack", but I see this written "sac" even in English texts).
A few more pictures (now that I'm back from "the most important of all the unimportant things in the world", i.e. football). Here you go cuttlegirl, a close-up of the tail end of the gladius in the laterally-preserved animal. The white layer at the top is made of francolite (carbonate fluorapatite) - it fluoresces spectacularly under UV light.
OK, that explains the dendrites dorsally, I had trouble making sense of it otherwise I take it the ink has a tendency to solidify post mortem, for such a three dimensional shape to remain, even following fossilization?
Thanks Hajar. That is so cool, cuttlebones today have a top layer (that corresponds to the francolite layer) and then the chambers are laid down laterally and ventrally from the top layer.
I found a google book that has nice drawings of the anatomy of some cephalopods. Starts on page 559. It's an old book (1861), but with incredibly detailed illustrations. It doesn't concentrate on cuttlefish as much as I would like, but has some octopus anatomy and Nautilus anatomy.
Also, how do you differentiate between the ink sac and not the stomach? In other words, how did you determine that it was the ink sac and not the stomach? The ink sac is connected to the stomach, but ventral to the stomach. See figure 221 on page 535 of the second book.
Hi cuttlegirl, it's about 10 cm long and has shown all the repertoire of colours (including the neon blue line) and textures (smooth to covered in tubercles) that I've seen in the wild ones here so I'd guess Sepia pharaonis.
I did! Here's a picture of an eye which I find fascinating. It's a very photogenic animal, now named "Ramses". The eye of the laterally-preserved coleoid shown above is also remarkable and I'll take a close-up of that a little later.