The previous oldest known fossil snakes date from ~100
million year old sediments (Upper Cretaceous) and are both
morphologically and phylogenetically diverse, indicating that snakes
underwent a much earlier origin and adaptive radiation. We report here
on snake fossils that extend the record backwards in time by an
additional ~70 million years (Middle Jurassic-Lower Cretaceous). These
ancient snakes share features with fossil and modern snakes (for
example, recurved teeth with labial and lingual carinae, long toothed
suborbital ramus of maxillae) and with lizards (for example, pronounced
subdental shelf/gutter). The paleobiogeography of these early snakes is
diverse and complex, suggesting that snakes had undergone habitat
differentiation and geographic radiation by the mid-Jurassic.
Phylogenetic analysis of squamates recovers these early snakes in a
basal polytomy with other fossil and modern snakes, where Najash rionegrina is sister to this clade. Ingroup analysis finds them in a basal position to all other snakes including Najash.