Four-Legged Snake Fossil Discovered
It seems that the final pieces of the puzzle that was the evolution of snakes are finally slotting into place. Earlier this year we reported here about the discovery of four new fossil species which hinted at a terrestrial rather then marine origin for these animals and which seemed to promise new discoveries just around the corner. Then, late last month (July 2015) yet another new fossil was announced, this time by the University of Portsmouth, and it was something particularly special.
Tetrapodophis amplectus lived around 110 million years ago during the Early Cretaceous. The species was discovered in Brazilian rocks which were once part of the great southern super-continent of Gondwana, and it would have looked a lot like a modern snake. It had the typical elongated profile and it seems to have been a voracious predator as this specimen was found with the bones of its most recent prey still in its stomach, which seems to have been a salamander-like animal. The preservation of this new snake is so excellent in fact that the imprint of the trachea and even belly scales are visible on the fossil. The most remarkable thing about Tetrapodophis though was that it still had four discreet legs.
For a long time palaeontologists have been debating when and why snakes originally lost their legs. Did they evolve from marine lizards which lost them in efforts to become ever more streamlined? Or did they evolve from land-dwelling burrowers who used their elongated shape to slip through the soil? Recent fossil discoveries had been favouring this latter hypothesis and Tetrapodophis seems to confirm this. It lacks any evidence that it was aquatic and instead seems to have lived on the banks of a large salt lake surrounded by succulents. Its legs are tiny, barely 1cm long with perfectly formed elbows, wrists and hands all equally minute. In fact the animal was only around 20cm long in its entirety but evidence suggests it was also only a juvenile so the adults could have been much larger. Interestingly the hands and feet also show evidence of adaptations for grasping, perhaps to help hold struggling prey.
This latest in a recent line of remarkable serpent fossils finally seems to answer the question about where snakes evolved and it promises to help scientists to begin to answer the question of ‘why’ as well.
Martill, D.M., et al. 2015. A four-legged snake from the Early Cretaceous of Gondwana. Science. 349. DOI: 10.1126/science.aaa9208
Featured Image: Timber Rattlesnake. Source: Wikimedia Commons