Paleontology • 2015 

The Oldest Known Snakes from the Middle Jurassic-Lower Cretaceous provide insights on Snake Evolution

Ancient snakes: (top left) Portugalophis lignites (Upper Jurassic) in a gingko tree, from coal swamp deposits at Guimarota, Portugal;  (top right) Diablophis gilmorei (Upper Jurassic), hiding in a ceratosaur skull, from the Morrison Formation in Fruita, Colorado; (bottom) Parviraptor estesi (Upper Jurassic/Lower Cretaceous) swimming in freshwater lake with snails and algae, from the Purbeck Limestone in Swanage, England.

Illustrations: Julius Csotonyi |  DOI: 10.1038/ncomms6996

ABSTRACT 

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.

  

 Michael W. Caldwell, Randall L. Nydam,  Alessandro Palci and Sebastián Apesteguía. 2015. The Oldest Known Snakes from the Middle Jurassic-Lower Cretaceous provide insights on Snake Evolution. Nature Communications. 6. DOI: 10.1038/ncomms6996.

researchgate.net/publication/271443533_The_oldest_known_snakes_from_the_Middle_Jurassic-Lower_Cretaceous_provide_insights_on_snake_evolution

http://squamates.blogspot.com/2015/01/new-old-snakes-revise-earliest-date-for.html

The oldest known snakes from the Middle Jurassic-Lower Cretaceous provide insights on snake evolution

• Michael W. Caldwell,
• Randall L. Nydam,
• Alessandro Palci
• & Sebastián Apesteguía

Published -27 January 2015

Abstract

• Abstract•
• References•
• Author information•
• Supplementary information

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.