All vertebrates that live on land--from humans to alligators to birds--are collectively known as tetrapods, meaning four feet. The name sticks even though the legs to which two of these feet are attached have become arms in humans and wings in birds. In snakes, the change was even more radical: they lost all four of their limbs. One of the few remaining signs of their limbed heritage is the presence of vestigial hips imprisoned in the rib cage.
How did snakes come to be? The distinctiveness of the animals obscures their ancestry. Their scales, eggs, and subtle features of their skulls show them to be descended from lizards, but it’s been difficult to link them to any specific group. Unable to pin them down taxonomically, paleontologists have been able to construct only the flimsiest of scenarios for how snakes lost their limbs. But this confusion may now dissolve, thanks to ...
