A team of paleontologists led by Prof Michael Caldwell of the University of Alberta, Canada, has found the fossilized remains of four ancient legged snakes between 140 and 167 million years old. The discovery is changing the way scientists think about the origin of snakes, and how and when it happened.
Portugalophis lignites in a gingko tree. Image credit: Julius Csotonyi.
The previous oldest known fossil snakes date from the Upper Cretaceous (100 million year ago) and are both morphologically and phylogenetically diverse, indicating that snakes underwent a much earlier origin and adaptive radiation.
A new paper in the journal Nature Communications reports on fossils of four legged snakes (named Eophis underwoodi, Portugalophis lignites, Diablophis gilmorei and Parviraptor estesi) that extend the record backwards in time by an additional 70 million years.
One of the four newly discovered species, Eophis underwoodi, is the world’s oldest known snake. It lived during the Bathonian stage of the Middle Jurassic, about 167 million years ago. Its fragmentary remains were recovered from Kirtlington Cement Works Quarry in Oxfordshire, England.
Portugalophis lignites lived during the Kimmeridgian stage of the Upper Jurassic, between 157 and 152 million years ago. Its fossils were discovered in coal deposits near Guimarota, Portugal.
Diablophis gilmorei hiding in a ceratosaur skull. Image credit: Julius Csotonyi.
The North American species, Diablophis gilmorei, was found in river deposits from some distance inland in western Colorado. It lived during the Kimmeridgian stage of the Upper Jurassic.
The fossils of Parviraptor estesi were found in Durlston Bay, Dorset, England. The species lived during the Berriasian stage of the Early Cretaceous, between 145 and 140 million years ago.
According to Prof Caldwell and his colleagues, their study makes it clear that the sudden appearance of snakes some 100 million years ago reflects a gap in the fossil record, not an explosive radiation of early snakes.
Parviraptor estesi swimming in freshwater lake with snails and algae. Image credit: Julius Csotonyi.
“From 167 to 100 million years ago, snakes were radiating and evolving toward the elongated, limb-reduced body shape characterizing the now well known, 100-90 million year old, marine snakes from the West Bank, Lebanon and Argentina, that still possess small but well-developed rear limbs,” Prof Caldwell said.
“The identification of definitive snake skull features reveals that the fossils – previously associated with other non-snake lizard remains – represent a much earlier time frame for the first appearance of snakes.”
“Based on the new evidence and through comparison to living legless lizards that are not snakes, the paper explores the novel idea that the evolution of the characteristic snake skull and its parts appeared long before snakes lost their legs.”
“The distribution of these newly identified oldest snakes, and the anatomy of the skull and skeletal elements, makes it clear that even older snake fossils are waiting to be found.”
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Michael W. Caldwell et al. 2015. The oldest known snakes from the Middle Jurassic-Lower Cretaceous provide insights on snake evolution. Nature Communications 6, article number: 5996; doi: 10.1038/ncomms6996
