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Hi to all,
             decided to get some prep practice in the other day and had this partial ammonite, which I'm fairly sure is Androgynocerous capricornus, from St Gabriels Mouth, Charmouth, Dorset.
The centre of it still had the matrix attached, so this was what I decided to remove to get some prep practice in and I was surprised to find that the inner 'whorls' were 'waffer' thin.
As can be seen from the photos the inner cast has been exposed after prep and would suggest that the thin inner whorls were not in this condition during life and happened post mortem.
I also prepped two other smaller partial examples of the same species, from the same location, and these also had very thin inner whorles.
Any ideas what has caused this?, my only theory is that after or during death they may been exposed to sunlight and desiccated?.


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The body chamber, being empty after the decay of the animal, was quickly filled with sediment, whereas the chambered part of the shell usually takes longer to fill through the sipho. As such, the body chamber provided more resistance against sediment pressure and the inner whorls where squashed.
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Thank you AndyS, that does make sense.
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