Oh a 1-1 formation, I've never seen this before for Natrix natrix, great !

I think this may have something to do with abnormal temperatures during incubation of that particular snake, I'm not sure, but I remember reading an article about the scale formation and there's a link with malformation and the lack of stable incubation conditions.

I get the feeling I'm in for some telling off from the more scientific people of the community !

What's for sure is that I would have been very confused if I only had a shed of that snakes head and was trying to identify the species !

Very interesting, thank you for sharing 

Dear Tony,

Dan urges me to try (to pretend) to be a good scientist ;-).

Haven't seen (or at least noticed) this either in Natrix natrix. Was it the same at the other side of the head? I'd guess, this is exceptional, but not necessarily due to genetics or anything similar. I believe that this kind of characters tends to follow a certain (in this case, of course, discrete and not continuous, because there cannot be e.g. 1,734 scales) frequency distribution, with the occurrence of a single scale being exceptional but not impossible at the one offshoot, and e.g. 4-6 scales at the high end. Often, these exceptions occur at only one side of the head or body.

This makes me think of some scale features of Iberolacerta lizards, in which e.g. presence or lack of contact between certain scales has been shown to occur at a certain percentage (e.g. 75% of specimens have those scales touching each other). This latter example shows a (larger) 1/4 chance of 'abnormality ', which is not a genetics thing, but a normal feature of the species' morphology. While this example is still discrete ("yes or no" = there's either contact or not), this also tends to be more of a continuous feature, if you regard the relative amount of contact between these scales (no contact, barely touching, large contact zone, ...).

Not really full-proof, but still thought I'd share my thoughts. Hope they're worth anything.

g's,

J. 

That’s interesting Daniel and Jeroen,
I have only ever seen scale malformation twice on Natrix, both snakes were found on the same site I will post a picture of the other.
Jeroen the Natrix in the first picture has two scales back of its eye on the opposite side of its head.

I will tell you a bit about the history of this site where I photographed the Natrix, my farther is a amateur naturalist and in the 1940-50s he said that Grass snakes where very common on that site and on a number other sites in East Yorkshire were I live.
In the 60s and 70s though there was a steep decline in the populations brought about by a changes in agricultural policies, most notably the draining of wetland and the use of chemicals like DDT, although harmful chemicals had been banned by the 80s the damage had been done, populations of Raptors were decimated in the 70s, all Raptors suffered badly, but Sparrow hawks and Buzzards had become extinct in East Yorkshire, through the 80s and 90s though the Raptors recovered well, Sparrow hawks and Buzzards once again are a common sight here.
Sightings in the 80s and 90s of Grass snakes were very rare, I could go a hole year without seeing one, and at times if it wasn’t for the odd fisherman saying they had seen one, I would have thought they had become extinct here too.
From the late 90s I have seen a steady increase in them, on the three main sites I visit I will see at least one most visits, some times two or three, so its looking good for Natrix here, but I don’t think they will ever be described as very common again.

Could the fact that the population of Natrix became so very low on this site, have anything to do with the scale malformation!

Jeroen, the other side of its head on this one is normal with three scales
http://i794.photobucket.com/albums/yy222/11palmer/Picture1007.jpg

Regards

Tony