Friday mystery object #40 answer

On Friday I gave you this skeleton to identify:

It looks a bit like a snake, but there are a couple of give-aways that mean it must be something else. First of all, snakes may look like they’re all tail, but actually they have quite short tails in relation to their body length (hint – the tail starts just after the ribs end) and second, a snake’s skull has a very open light structure (as I’ve discussed before). Both of these snaky features can be seen in this image taken by dbking:

Viperid snake skeleton (image by dbking)

Viperid snake skeleton (image by dbking)

So, if it’s not a snake, what is it? There are quite a few animals that have a long slim body with no limbs, from eels to caecilians to a variety of lizards (including, but not restricted to snakes, which are a discrete subgroup within the lizards). However, this is not an eel because their ribs don’t form a cage – they form vertical projections for their muscles to work against, it’s not a caecilian because they have even shorter tails than snakes, which leaves us with the non-snaky legless lizards (as recognised by Gimpy).

Legless lizards crop up in at least three major groups of lizard (not counting snakes) so there is a fair amount of choice out there. The Amphisbaenia are really weird and the mystery object doesn’t have the right skull shape to be one of them. The Pygopodidae are legless members of the same group as the geckos – and the mystery object could probably be one of them, except it’s not. It is in fact a member of the Anguoidea (more particularly the Anguidae) and it was identified correctly by Jim (and seconded by Neil) as being a European glass lizard Ophisaurus apodus (Pallas, 1775).

These animals apparently get the name “glass lizard” from the fact that they break quite readily – by which I mean that their tails fall off when they’re handled. This is quite a common predator avoidance characteristic in lizards and the tail can regrow, albeit shorter and usually darker in colour than the original tail. The break in the tail visible in this specimen is in about the right place for where it would be shed (whether this is deliberate, a result of the shape of the vertebrae involved in the shedding mechanism, or pure chance – I can’t be sure until I re-examine the specimen).

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