Snakes are muscle-noodles that have been biting and thriving for at least 140 million years. And while they’ve gone from squirming alongside dinosaurs to living alongside humans on every continent besides Antartica, one thing has essentially remained the same: the snakes themselves. This seemingly time-resistant state of homeostasis is underscored by the recent discovery of ancient snakes preserved in Late Cretaceous amber.

An international team announced Wednesday in the journal Science Advances that they discovered two snakes trapped within the golden fossilized resin — one of which is considered the oldest known fossilized baby snake. This unique and very tiny snake hatchling, the Xiaophis myanmarensis, has anatomy comparable to living snakes despite its estimated 99 million years of age. With 97 vertebrae and rib bones, it’s most similar to the modern-day Asian Pipe snake, a smooth and glossy invertebrate that boasts a powerful jaw.

The snake’s anatomy is evidence that its general body shape has been conserved for a very long time, study co-author and University of Alberta professor Michael Caldwell, Ph.D. explains to Inverse.

“This was a surprise,” he says. “What it really means is that modern ‘snakeness’ evolved at least 100 million years ago.”

ancient snake
Detailed view of scales belonging to the ancient snakes.

These fossilized snakes were found in the Southeast nation of Myanmar; but when they were alive and slithering, their home existed within Laurasia, one of the two mega-continents that emerged when Pangea split. The scientists were able to pinpoint the snake’s ancient origins through the use of uranium-lead dating, which revealed that the amber that encased both snakes is around 99 million-years-old.

The amber itself is novel because of its ability to serve as a spyglass into the past. Encapsulated within it are fragments of the insects and plants that lived alongside the snakes, making it a mini time-capsule of the Mesozoic era.

“The amber preserves a moment in time when the droplet struck the snake, the bugs, and the plants caught up in the resin,” says Caldwell, “and as such, provides detailed information you cannot get from the rock record, on the ancient environment in which this little snake was living — a forest.”

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Microphotography of the snake vertebrae and ribs of the adult snake specimen. 

While the novelty of a baby snake specimen revealed a previously untenable look at the developmental process underwent by ancient snakes, there is still so much about snakes that is not understood. According to Caldwell, “just about everything about snakes is a mystery.” That includes their origins, who among lizards their closest relatives were, the evolution of complete limb-loss, their unique skull morphology, and why their forelimbs disappeared before their rear-limbs. And while these snake specimens are old, their species as a whole is much older.

“We must continue to look in even older rocks if we wish to understand the origin of snakes,” says Caldwell, “not just their subsequent specializations and evolution.”