Fossils Trapped in Amber Offer Clues to the Origins of Snakes
Posted July 18, 2018 4:07 p.m. EDT
In 2016, Lida Xing was combing the amber markets of Myanmar when a merchant enticed him over to his booth with what he said was the skin of a crocodile trapped in amber. When Xing inspected the specimen through its honey-colored encasement and noticed the diamond-shaped pattern of its scales, he realized what he was holding was actually a 99-million-year-old snakeskin.
Xing, who is a paleontologist from the China University of Geosciences in Beijing, had previously recovered a feathered dinosaur tail and a baby bird in the amber markets. But he said that of the hundreds of thousands of amber pieces discovered in the area, no one had ever before found a snake.
He purchased the snakeskin and set up a meeting with Michael Caldwell, a snake paleontologist at the University of Alberta. A few minutes before Xing boarded his flight to Canada, a different colleague alerted him to another recently discovered snake specimen that was more amazing than the first: Entombed in a silver-dollar-sized chunk of amber was a baby snake.
“The fossil is the first baby snake and the oldest baby snake to yet be found,” said Xing. Before this finding, paleontologists had not uncovered a fossilized baby snake even in the rock fossil record, said Caldwell.
Xing and Caldwell reported their findings from the two specimens Wednesday in the journal Science Advances. The work provides insight into the evolution of snakes, their early-stage anatomical development and their prehistoric spread across the globe.
Only the bottom half of the baby snake’s sinuous body was preserved in the amber, which is fossilized tree resin. Because the skull was missing, the people who found the fossil thought the tiny creature inside was either a centipede or millipede.
But closer inspection revealed its bones. And through the use of a micro-CT scanner and a synchrotron, scientists confirmed that the specimen was a baby snake, a new species they named Xiaophis myanmarensis. It resembles existing species of pipe and grass snakes.
The researchers determined the fossilized snake was either an embryo or a newborn based on the development of its spinal cord. Like modern baby snakes, the preserved baby had tiny vertebral bones but a large spinal cord tube, according to Caldwell. That’s a telltale sign that the snake was still developing, as well as the first direct evidence that the developmental processes seen in a baby snake’s spine were established at least about 100 million years ago and have remained relatively unchanged since then.
The researchers could not say whether or not the shed snakeskin belonged to the same species as the baby snake.
Ryan McKellar, a paleontologist from the Royal Saskatchewan Museum in Canada and an author on the paper, said the fossilized snakeskin was trapped along with plants, cockroaches and insect droppings. Those clues indicated that the ancient snake lived in the forest. That may seem like a likely locale for a slithering snake, but before this discovery, paleontologists did not have direct evidence of snakes living in forests during the Mesozoic Era.
Scientists are not sure where snakes originated from and how they spread throughout the world. The new specimens offer clues for one potential pathway for their prehistoric movement around the planet, said Dr. McKellar.
Some 100 million years ago when the snakes became trapped in tree resin, Myanmar was part of a migrating island between present-day Asia and Australia. That island eventually floated to the coast of Laurasia, a supercontinent that then included present-day Europe and Asia.
“These snakes would have been along for the ride,” he said.