more Hollingworth ammonite

Neale Monks

Jun 29, 2003
This might amuse. I found the original on one of my back up disks. Enjoy, but don't spread around outside of this forum. The copyright certainly isn't mine.

It's the Hollingworth soft body ammonite illuminated using UV light. Shows some of the features rather better than regular lighting.


Looking at this picture brings up a few questions. Why is the siphuncle not seen attached to the ventral posterior part of the living chamber? Is the siphuncle a very low priority organ? It seems to me that it would be a higher priority in a shelled cephalopod than a naked cephalopod. Is there any form of siphuncle in squid or octopusses? Do cuttle bones have a siphuncle? Is the siphuncle even an organ, or is it just part of the mantle?

No, squids and octopuses don't have siphuncles. Yes, cuttlefish do. In fact the whole shell in a cuttlefish is one big siphuncle. There is tissue going through the whole thing and that's why it has thousands of tiny chambers instead of a just a few big ones like an ammonite or nautilus.

I don't pretend to understand the picture I posted. It is a very mysterious fossil and it's a great shame that the people who worked on it haven't published more.


Thanks Neale,

I guess all fossils are mysterious in a way, some more so than others. If we knew all the answers there wouldnt be any questions, then what would we do?