Polymorphites or …endless forms most beautiful…

The title of this article is not only part of the conlusion of Charles Darwin´s “On the Origin of Species…”, (and derived thereof the title of Sean B. Carrolls excellent book on “Evo Devo”),
but also very true for the next group of ammonites I´d like to show you : The genus Polymorphites.
The name says, translated, “of multiple form”, and this alludes to the large variety of species / intra-species variation in this genus.
Polymorphites polymorphus , intermediate form, 2 cm

Polymorphites polymorphus , intermediate form, 2 cm

Polymorphites polymorphus lineatus, 1,8 cm

Polymorphites polymorphus lineatus, 1,8 cm

Polymorphites polymorphus interruptus, 1.8 cm

Polymorphites polymorphus interruptus, 1.8 cm

I´ve followed HOFFMANN 1982´s naming of the ammonites as subspecies. These are just the ones I could relatively easily put a name to since their relatively characteristic representatives, there are some more in my drawers that need sorting through and grouping.
On the Yorkshire coast these can be found in the lower lias, jamesoni zone, polymorphus subzone, and their phragmocone is usually relatively small and preserved in stable pyrite while the body chamber is flattened or not preserved at all.
I add the word “stable” here without parentheses or doubt, since this pyrite really seems to be stable, I´ve seen Polymorphites specimen in Whitby museum that probably have been found 100 years or longer ago and show no sign of the dreaded pyrite decay.
Due to more or less oxidization, and probably some intricacies in the composition of the pyrite, the ammonites show a natural light copper colour on the side embedded in the rock, while the upper side is usually poslihed to a more golden tone. On the ammonites shown I’ve only removed some small surplus of matrix with a needle, carefully brushed them under water with an old soft tooth-brush and gave them a good thorough but thin varnishing – they’ve kept their colour for many years. One where I did add the toothpaste to the toothbrush when cleaning it (it is really one of the best polishes !) of course lost its copper colour, but also stayed “silver” and decay-free after varnishing.
It´s a special delight to seem them magnified on the screen at approx. 5 x, most papers only picture them “life-size”, and this is, as you see from the pictures titles, usually only between 2 and 3 cm.
AndyS
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