#FossilFriday: A four-legged snake from Brazil points to the origins of modern snakes

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It sounds like a contradiction, but palaeontologists from the UK and Germany have discovered a snake with legs! This stunning fossil, found in Brazil, dates from the time of the dinosaurs in the early Cretaceous period, which began more than 145 million years ago. The new species, Tetrapodophis [meaning four-legged] amplectus, has the characteristic anatomical features of a snake, with the long body, relatively short tail and skull morphology we recognise in modern species. But clearly visible are four small yet perfectly formed limbs (enlarged images below), a new find in any fossil snake. From their shape and size, Dr David Martill’s team propose the limbs would have been functional, perhaps used to clasp prey or mates and hold them close to the body, but that they were not used in locomotion – the snake likely ‘slithered’ like those we see today. This new discovery not only points to the evolutionary origins of modern snakes in the ancient supercontinent of Gondwana (where the site would have been located at the time), but it reveals vital information about their ancestors. The skeletal structure indicates that snakes evolved from ground-dwelling or burrowing ancestors, not aquatic ones, as Tetrapodophis amplectus shows no adaptations to life in water but has the robust skull shape seen in burrowing species. It also appears that Tetrapodophis amplectus was carnivorous, as it possessed long, curving teeth and the flexible jaws that enable snakes to swallow larger prey, meaning it is more likely that insectivorous snakes evolved later. Even though there are older snake fossils, the exceptional completeness of this animal has vastly enriched our knowledge of serpentine evolution.

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Images courtesy of Martill et al. 2015. Read more here, and read the full paper here.

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