Help identify snake in Bolivia

Having rediscovered my interest for snakes lately it ocurred to me that maybe someone here could help me identify a snake I saw a few years ago in Bolivia. The picture was taken in the pampas of Madidi national park. The snake was very fast and I was trying to get a photo of it so I couldn't really see if it had the head of a viper or not. Sorry for the less than stellar quality of the photo :)https://uploads.tapatalk-cdn.com/202...2ab5a13db2.jpg

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I'm no expert on the snakes of Bolivia, but to me it looks like it might be a

• Palusophis bifossatus aka Rio Tropical racer

https://en.wikipedia.org/wiki/Palusophis_bifossatus

https://ball-pythons.net/forums/cach...-_REFON_-4.JPG

The pattern is similar, & there might be some natural variations to account for the difference; it doesn't look to me like any sort of viper- plus it is built like a racer, & by your description, it moves like a racer.