According to research published Tuesday in Nature Communications, we may need to slither back the clock on snake evolution.

In fact, we may have been pretty wrong about just how snakes evolved from the common ancestors they share with modern lizards. Until now, the oldest-known snake fossils were only about 100 million years old. The new study presents not one, but four new specimens that are much older -- dating back as many as 167 million years -- found in neglected museum collections around the world. And these older fossils show the long, thin skulls that distinguish snakes from lizards today. Many scientists previously believed that snakes became long and limbless before they evolved their distinctive heads.

"The skulls of these animals are much more snakelike than even I thought they would have been," said study author Michael Caldwell, a paleontologist at the University of Alberta. "Which means that this quality of snake-ness had clearly occurred much earlier than we'd thought."

That's not so shocking when you look at lizard evolution.

"We can recognize that most of the major groups of lizards were already present at the time," he said. So it seems that snakes were evolving at much the same pace, as opposed to undergoing some rapid deviation from lizards 100 million years ago.

The new fossils are just small fragments of snake -- enough to show that they had snake-like heads, but not much else. Caldwell feels fairly certain that they still have had four limbs at the time, but can't be sure.

Caldwell and his colleagues found the new specimens by digging through museum drawers instead of archaeological sites. Many museums have untapped fossil and skeleton collections just waiting for specialized researchers to examine them.

"The number of vertebrate paleontologists is pretty small, and the number who know anything about snakes is even smaller," Caldwell said. "It's easy to become a world expert when there are only eight of you."

Caldwell, who once focused on lizards, is now attuned to the skeletal differences that shout "snake."

"When you understand the comparative anatomy, it's night and day," he said of snake and lizard fossils. But people who aren't schooled in the differences (most people) will assume they're lizards -- or something else entirely.

"You'll go into a museum and find things in the fish drawers that are actually snakes," Caldwell said. "It's a pretty common thing."

He and his colleagues have spent a decade searching through these dusty treasure troves, and he says there's a lot more work to do. Now that we have snake fossils from 167 million years ago, they'll have to fill in the gap in the record between these and the 100 million-year-old fossils previously assumed to be the oldest.

Read more: