Discussion of the Reconstructions of Nautiloids and Ammonoids

Thanks ever so much for the picture Kevin. The endocones are really clear. I'm flabbergasted at exactly how wide the siphuncle is, I certainly did not expect to see that. All the pictures of the siphuncle I've seen in ammonoids tend to be much, much smaller in ratio to the diameter of the shell, so this was a surprise.

What an interesting solution to the problem of counterbalancing weight and bouyancy whilst maintaining stability.
 
Following the addition of Belemnotheutis, I have now updated all the entries to provide links to images of the species listed, and a few related research papers.
 
Cheers Kevin!

There may be better links out there to some of the species listed, so if you find any, please just shout and I'll add them.

Much appreciated.
 
Hi everyone,

Sorry for popping in to the thread this late, but......

Some sources say that aptychi are elaborate lids, while others say "jaw apparatus". By that word, are they actually parts of ammonite's beak, or even analogous to coleoid beaks?

I have seen that some of them (those preserved in place) are simply too big to the point almost blocking the living chamber - but not quite lids either. If they really are jaws, I think that would be pretty awkward (beside being scary) with jaw that big :hmm:

Thanks everyone !

-agha.]
 
hmmmmm, yeah, the subject itself is a great debate until now :hmm:

I wonder if this link actually says something. Sorry, but I find it rather difficult to understand. It even mentions crustacean carapaces as a possible identity of the aptychus. Why crustaceans ? :confused:

thanks,

-agha.]
 
Allonautilus;81866 said:
hmmmmm, yeah, the subject itself is a great debate until now :hmm:

I wonder if this link actually says something. Sorry, but I find it rather difficult to understand. It even mentions crustacean carapaces as a possible identity of the aptychus. Why crustaceans ? :confused:

thanks,

-agha.]

One of those references (about crustaceans) is from 1882 - not that I am saying that the work isn't still relevant today, but maybe there is more information about aptychi today.

There are some small crustaceans (like ostracods) that have two paired "shells."
 
The following is from the Link provided:

The principal purposes of this study are to examine and describe the "spathiocarids" of the Cleveland and Chagrin shales, investigate their relationships with similar Devonian taxa, and attempt to provide solid identification of their nature, if possible. This latter goal was not fully realized, but two of the most likely alternatives have been eliminated. It is probable that these fossils should be referred to the Cephalopoda.

It seems alot of thin carbonaceous films have been referred to Spathiocaris, a phyllocarid crustacean, and a few other taxa, but this report puts them in synonymy and refers them to 7 species of Sidetes Giebel, 1847, and interprets them as cephalopod jaw elements.

A few crustaceans have been found in fossil cephalopod shells, the radular teeth in the missing photo on the other thread looked like crab legs, so these all have to be taken into account. :biggrin2:
 
I've just added Cameroceras. Not much info to go on out there in net-world so the details are a little vague I'm afraid.
 
The figure was already there Kevin. If I'd made the image I would have used a London Transport bus conductor instead of a Japanese Manga warrior.
 

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