A paper published last month set fire to the debate: a four-legged snake fossil was described by a group of scientists from the UK, led by Dr David Martill, a professor from the University of Portsmouth. That’s right, a snake with four tiny legs. And you thought that snakes would only have legs when pigs fly!
The newly discovered creature was given the name of Tetrapodophis amplectus. Tetrapodophis, Greek for “four-footed serpent”, and amplectus, Latin for “embracing”. No one had described a 4-legged snake before. Tetrapodophis amplectus was found by Dr Martill during a field trip with students in the museum Solnhofen in Germany, when he noticed this small piece labelled “unknown fossil”.
“All of a sudden my jaw absolutely dropped.” He then realised, that small little “snakey” creature had tiny little legs!
Martill and his colleagues analysed the fossil and deduced it came from north-eastern Brazil. Before it was displayed at the museum and accidentally found by Martill, the fossil was housed in a private collection for decades.
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A tight hug of life or death
Tetrapodophis amplectus lived approximately 130 million years ago, when Africa and America were still together in one huge supercontinent called Gondwana. It was a great great great great relative to modern snakes.
This ancient snake-like animal is 20cm long, had hooked sharp teeth, joints in its jaws (characteristics that allow snakes to expand their jaws for swallowing its meal whole) and a flexible spine, which Martill and colleagues estimate could be used to constrict prey.
The limbs are greatly reduced yet highly specialised, suggesting that they were functional. The arms are 4mm long, while the legs are 7mm. The presence of slender “fingers” and well-developed phalanges resemble birds’ claws—yet the size makes it unlikely that these four tiny legs were used for locomotion. The resemblance to bird feet suggests they were used for holding prey while the “snakey” body wrapped around an unfortunate small vertebrate—the animal equivalent of Judas’ kiss. Another option was they could be used to hold a partner while mating.
T. amplectus had around 160 vertebrae before its tail and still retains its hand and feet, while, on average, once achieving a length of 70 vertebrae, snakes and lizards start to lose limbs. The fossil had preserved snake-like scales, skull and body shape compatible with serpentine locomotion and adaptations for burrowing (again, tiny legs are a great example of those).
This would indicate that the early snakes did the same. The gut content was preserved so the researchers were able to identify bones from the hugging snake’s last meal.
To be or not to be [a snake]?
Tetrapodophis amplectus might not be a snake. Wait, what? It really looks like one to most of us, right? At this point you might have been convinced that Martill did find the missing link between lizards and snakes, and that it would soon be in really cool documentaries and movies, right?
Well, according to Susan Evans, a paleobiologist of the University College of London, snake-like bodies appeared many times in history in different species of snakes and lizards—at least 26 times.
“I’m trying to carefully sit on the fence as to whether this is actually a snake,” said Susan to Science magazine. Michael Caldwell, a paleontologist is also unsure. “I think the specimen is important, but I do not know what it is,” he stated in an interview for National Geographic. He claims that the vertebrae and the lack of association with another bone that occurs in every living and extinct reptile is enough to doubt that the four-legged snake is even a reptile, let alone a snake. He believes it could be an ancient amphibian instead.