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P. parkinsoni has a compressed spiral shell with strong, biplicate ribbing and lateral tubercles. Internally the shell is divided up into chambers
Ammonoids were soft-bodied organisms with an external shell.
Parkinsonia parkinsoni has a compressed spiral shell with strong, biplicate ribbing and lateral tubercles.
Internally the shell is divided up into chambers.
Chambers would have been filled with gas acting as a buoyancy aid.