The Osteology of Decorative Plastic Halloween Skeletons, Part 9: Snakes

It is interesting to note that all tetrapods (the land vertebrates, i. e. amphibians, reptiles, birds, and mammals) have essentially the same skeleton.  The bones vary in size and shape between species, but whether it’s a salamander, an armadillo, or a condor, the basic skeletal elements are mostly the same.  The biggest potential variation is that some elements can be lost due to evolution.  Snakes (which are, evolutionarily speaking, a highly successful group of legless lizards) are an extreme case, lacking almost everything except the skull and the vertebrae and associated ribs.  (There is also a hyoid bone and, in a few species, tiny remnant hind limbs.)

There are numerous plastic snake skeletons available.  

This one (available at Amazon for $14.94) lacks ribs entirely.  

This other one (available at Target for $12.60) has ribs, although they are not exactly realistic.  

In both of the above cases, the skull is much too massive and lizard-like, unlike the highly specialized, and generally weird, skulls of actual snakes.  

There is even this two-headed skeleton, which was once available at Spirit Halloween.  It suffers the previously observed problems of lacking ribs and having an unsnakish skull.  But two-headedness is indeed a real phenomenon in snakes and other reptiles.  It has been known to occur in the squamates (the lizard and snake group), the turtles, and even Hyphalosaurus, a Cretaceous choristoderan, but as far as I know there are no examples from the archosaurs (crocodilians, pterosaurs, dinosaurs, and birds).