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AZ: New Research on World's Oldest Snake Fossils Changes Understanding of Serpents

January 28, 2015

by Office of Communications

Artist’s representation of ancient snakes, some of which have been mistaken for lizards in museums around the world. (Julius T. Csotonyi)

A new paper from an international group of researchers, led by Dr. Michael Caldwell, Department of Biological Sciences, University of Alberta, Edmonton, Alberta, and including Dr. Randall Nydam, Midwestern University, Arizona, reports on the fossilized remains of four ancient snakes that are between 140 and 167 million years old - nearly 70 million years older than the previous record of ancient snake fossils - that are changing the way we think about the origins of snakes, and how and when it happened.

The very oldest of these archaic snakes, Eophis underwoodi, is from Southern England, near Kirtlington, is known only from very fragmentary remains and was a small individual. The largest of these new snakes, Portugalophis lignites, from coal deposits in Portugal, near Guimarota, is thought to have been nearly a meter or more in length.  Several of these ancient snakes (Eophis, Portugalophis and Parviraptor) were living in swampy coastal areas on large island chains in western parts of ancient Europe, while the North American species, Diablophis gilmorei from Western Colorado, was found in river flood deposits some distance inland from the ancient coast. The findings have been published in the prestigious peer-reviewed journal Nature Communications.

The study explores the idea that evolution within the group called 'snakes' is much more complex than previously thought. Importantly, there is now a significant knowledge gap to be bridged by future research as no fossils snakes are known from between 140 to 100 million years ago. This new 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.  From 167 to 100 million years ago, some 70 million years, snakes were radiating and evolving towards the elongate, limb-reduced body plan characterizing the now well known, ~100-90 million year old, marine snakes from Argentina, Lebanon, and the West Bank, that all still possess small but well developed rear limbs. "These fossils already extend the known age of snakes by more time than between today and the end of the age of dinosaurs," says co-author Randall Nydam, Ph.D., Professor of Anatomy. "As is often the case, the distribution of these new oldest snakes, and shared anatomy of the skull and skeletal elements, particularly of the jaws, makes it clear that even older snake fossils are waiting to be found."

Based on the new evidence and through comparison to living legless lizards that are not snakes, the paper explores the unique idea that the evolution of the characteristic snake skull and its parts appeared long before snakes lost their legs. The identification of definitive snake skull features reveals that the fossils, previously associated with other non-snake lizard remains, represents a much earlier timeframe for the first appearance of snakes.  The concept of how snakes originated and evolved needs to be reassessed in light of this new information, and the unique ideas presented in this paper.

The authors of the paper include lead author Michael Caldwell, Ph.D., Professor and Chair, Department of Biological Sciences, University of Alberta; Edmonton, Canada; Randall Nydam, Ph.D., Professor of Anatomy, Midwestern University, Glendale, Arizona, U.S.A.; Alessandro Palci, Ph.D., Postdoctoral Fellow, South Australian Museum, Adelaide, Australia; and Sebastián Apesteguía, Ph.D., Head of Paleontology, Universidad Maimónides, Buenos Aires, Argentina.

Citation: Caldwell, M. W., Nydam, R. L., Palci, A., Apesteguía, S. The oldest known snakes from the Middle Jurassic-Lower Cretaceous provide insights on snake evolution. Nature Communications.5:5996 DOI: 10.1038/ncomms6996 (2014)

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