A delicate baby snake with a remarkably well-preserved skeletal structure is the first of its kind ever found fossilized in amber. At 99 million years old, the fossil is also the oldest snake known from a forested environment, paleontologists revealed today in the journal Science Advances.
The authors named the new species of snake Xiaophis myanmarensis. It’s likely related to some modern groups of snakes found in Southeast Asia, including nonvenomous Asian pipe snakes and sunbeam snakes, says study leader and National Geographic Explorer Lida Xing of the China University of Geosciences.
“No one has ever seen a fossilized baby snake of any kind whatsoever. And having this one be nearly a hundred million old is really quite amazing,” says coauthor Michael Caldwell, a fossil reptile expert at the University of Alberta in Edmonton, Canada.
“Whether or not these early snakes were giving live birth, which is common in modern snakes, or whether they were hatching from eggs, is unclear. But based on size and developmental stage, this thing was a [newborn],” he adds.
“I can't say if it was still in the egg, and it broke and the little guy was caught up in a blob of amber, or if it had just hatched.” (Also see the first fossil evidence that ancient snakes ate dinosaurs.)
Another piece of amber, also recovered from mines in Myanmar (Burma), holds a piece of probable snake skin with light and dark banding on its scales, which may have come from an adult Xiaophis or from another contemporary serpentine species.
The researchers can’t absolutely confirm that it’s snake skin, but the size, shape, and arrangement of the scales suggest that it is. If that proves to be the case, this will be the first piece of snake skin ever discovered in amber, too.
“The scales are organized as one would expect in a snake or a lizard, in diagonal rows. In this particular specimen, part of what makes it more snake-like is the diamond shape of the scales,” Caldwell says. “Most lizards don't show that same kind of diamond shape and pattern of overlap in the scales.”
The rich amber deposits from Myanmar’s northern province of Kachin have previously offered up well-preserved fossils of birds, the oldest known rain forest frogs, ancient blood-sucking ticks, and even a feathered dinosaur tail.
Xing says he acquired the new skin specimen in early 2016 for the Dexu Institute of Paleontology in Chaozhou, China, from a Burmese fossil dealer who believed it was crocodile skin.
The second specimen came to his attention in the summer of that year, and was initially thought to be a centipede or millipede. Its true identity was confirmed using advanced x-ray scans made at the Shanghai Synchrotron Radiation Facility, which helped the team create very detailed 3D models of the internal anatomy of the fossil.
At less than two inches long, the snake is very tiny and difficult to see clearly with the naked eye, but the x-ray scans allowed the team to carefully study the shape and position of its bones, including a remarkable 97 vertebrae or backbones. (Here’s how x-ray scans also revealed the flight style of a famous birdlike dinosaur.)
Based on that data, it seems the ancient snake is similar to other snakes known from the southern supercontinent of Gondwana, which existed in the late Cretaceous. That may indicate the chunk of land that became Myanmar had previously broken off from the other southern continents, such as Australia, Africa, and India, before colliding with modern-day Asia, Caldwell says.
The tiny fossil also bears some features that are no longer present in living species, he says, such as V-shaped spurs of bone on the bottom of the tail vertebrae. The spurs likely protected an artery along the length of the tail, and may also have been useful for stability when snakes initially became limbless.
“There are no adequately preserved snakes that are significantly older, anywhere,” comments paleontologist John Scanlon at the University of New South Wales in Sydney, Australia. Furthermore, while lizard fossils are abundant in the northern continents that once made up the supercontinent of Laurasia, snake fossils are very rare.
“There are a number of other well-preserved fossil snakes around the same age, but they are from marine deposits around the Mediterranean and are thought to represent aquatic species. Xiaophis is clearly from a terrestrial environment and resembles terrestrial, mostly burrowing snakes,” he says.
The baby snake is missing its skull, which would have provided much more information about the animal’s ecology, feeding habitats, and relationships to other snakes, Scanlon notes. However, finding one snake in Burmese amber suggests that there are probably more waiting to be discovered and studied, he adds.
“We should certainly keep looking, not only in amber, but also in Mongolia and other places that relatives of Xiaophis could have then reached overland.”