The fossilized skeleton of the newly discovered snake species Hibernophis breithauptithat lived 38 million years ago in what is now western Wyoming, provides insight into the evolution and social behavior of its modern descendants. Credit: Jasmine Croghan

Ancient snakes have been unearthed, shedding light on the continent’s twisting past.

A recently discovered fossil snake kind in Wyoming is changing our understanding of snake evolution. This species, called Hibernophis breithauptilived 34 million years ago in North America. This discovery provides valuable insights into the origin and diversification of boas and pythons.

Hibernophis breithaupti has unique anatomical features, in part because the specimens are articulated — meaning they were found all in one piece with the bones still arranged in the correct order — which is unusual for fossil snakes. Researchers think it may be an early member of Booidea, a group that includes modern boas and pythons. Modern boas are widespread in the Americas, but their early evolution is not well understood. These new and very complete fossils add important new information, particularly about the evolution of small, burrowing boas known as rubber boas.

Behavioral insights and historical significance

There has historically been much debate about the evolution of small burrowing boas. Hibernophis breithaupti shows that northern and more central parts of North America may have been an important hub for their development. The discovery of these coiled snakes also provides the oldest potential evidence for a behavior we know of today: group hibernation.

“Modern garter snakes are known to hibernate in their thousands in burrows and dens,” said Michael Caldwell, a paleontologist at the University of Arizona who led the study with his former doctoral student Jasmine Croghan and collaborators from Australia and Brazil. “They do this to conserve heat via the effect created by the ball of hibernating animals. It’s fascinating to see possible evidence of this kind of social behavior or hibernation going back 34 million years.”

Reference: “Morphology and systematics of a new fossil snake from the early Rupelian (Oligocene) White River Formation, Wyoming” by Jasmine A Croghan, Alessandro Palci, Silvio Onary, Michael SY Lee, and Michael W Caldwell, June 19, 2024, Zoological Journal of the Linnean Society.
DOI: 10.1093/zoolinnean/zlae073