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90 million years ago, an ancient snake known as Najash had...legs. It is by no means the only snake to have limbs either. But what’s even stranger: we’re not at all sure where it came from.

Produced for PBS Digital Studios.

Thanks to Franz Anthony, Julio Lacerda and Studio 252mya for the snake illustrations. You can find more of their work here:
Julio Lacerda: https://252mya.com/gallery/juliolacerda
Franz Anthony: https://252mya.com/gallery/franzanthony

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References:
http://www.wienslab.com/Publications_...
Locomotion in sea snakes: http://onlinelibrary.wiley.com/doi/10...
Ear bones in mammals: https://www.ncbi.nlm.nih.gov/pmc/arti...
Skinks: https://www.livescience.com/3053evol...
Pachyrhachis lifestyle: http://www.tandfonline.com/doi/abs/10...
Snake defining features: https://www.ucl.ac.uk/museumsstatic/...
Hsiang & Field 2015 Summary: https://blogs.biomedcentral.com/bmcse...
2012: Zaher at al. think Dinylisia is a sister taxon to all extant snakes: http://onlinelibrary.wiley.com/doi/10...
2015 news story on Tetrapodophis: https://www.sciencemag.org/news/2015/...
Another 2015 story on Tetrapodophis: http://phenomena.nationalgeographic.c...
2015 news story on Eophis: https://www.scientificamerican.com/ar...
2017 thesis on mosasaurs that makes it quite clear that there’s still quite a bit unresolved in the evolutionary relationships: https://era.library.ualberta.ca/files...
varanids (monitor lizards): http://animaldiversity.org/accounts/V...
Coniophis (65 million years young): https://news.yale.edu/2012/07/25/few...
Toxicofera paper: https://bmcevolbiol.biomedcentral.com...
See the "Bitter Realities about Squamate Phylogeny" section on this page: https://www.geol.umd.edu/~jmerck/geol...
Tetrapodophis actually aquatic?, paper proposes: http://www.sciencedirect.com/science/...
2013 paper w/the 4000 species: https://bmcevolbiol.biomedcentral.com...
file:///home/chronos/ue54db2a63a5b8e4345d3372e31d0632282c76ec5/Downloads/apestiguiazaher_nature060001.pdf
https://www.nature.com/articles/natur...
2017: Norisophis http://www.sciencedirect.com/science/...
Nidophis: http://www.bioone.org/doi/abs/10.1080...
Coniophis: https://blogs.scientificamerican.com/...
https://www.livescience.com/27845sna...
http://www.sciencedirect.com/science/...
https://www.ucl.ac.uk/museumsstatic/...
https://www.ncbi.nlm.nih.gov/pmc/arti...
https://watermark.silverchair.com/j.1...
http://www.tandfonline.com/doi/abs/10...
https://blogs.biomedcentral.com/bmcse...