These 12 lizards were trapped in amber for 99 million years

Amber fossils in Myanmar give scientists a snapshot of lizard evolution.

|
Courtesy of David Grimaldi
A lizard preserved in amber from Myanmar forests.
|
Courtesy of Daza et al. Sci. Adv. 2016; 2 : e1501080
Lizards preserved in mid-Cretaceous amber.

Some 99 million years ago, 12 unsuspecting lizards stepped or fell into sticky tree resin and couldn't tear themselves loose in the forests of what is now Myanmar. Over time that resin fossilized into amber, preserving the little lizards for scientists to study later.

Now, researchers are looking to these prehistoric golden chunks to better understand how lizards have evolved. 

There was a diverse population of lizards living in the region at the time, the scientists report in a paper published Friday in the journal Science Advances. And they ran the gamut, with some quite similar to modern lizards – like geckos, wall lizards, and dragon lizards – and others like nothing known today.

"The assemblage is cool because it has some examples which are really, really modern and then others which are really, really old, and then others in between," study co-author Edward Stanley, a herpetology researcher at the Florida Museum of Natural History, tells The Christian Science Monitor. 

"In the amber we have things that are clearly gecko," says Dr. Stanley. The gecko-like prehistoric specimens have toe pads. Modern geckos use their toe pads to scale walls and perform other sticky-footed feats, but these prehistoric toe pads appear somewhat different. 

Other amber-preserved lizard specimens had been found with toe pads more similar to those on living geckos, which suggests that "even 100 million years ago geckos apparently already had evolved a well-diversified subset of tools for clinging onto surfaces," Stanley says.

Another block of amber could show "some kind of animal that was on the road to becoming a chameleon," Stanley says. And that specimen, at less than half an inch long, had probably just hatched before it met its demise.

A CT scan of the itty-bitty specimen revealed a skeleton similar to those of modern chameleons but also with features more like other lizards. "It's this interesting sort of halfway stop between a modern chameleon and the sister group to chameleons, which are the dragon lizards," Stanley says.

This specimen doesn't have the fused digits that today's chameleons have to help them live in trees. But, like a chameleon, it has a shorter spine with fewer vertebrae than its cousin lizards. It also has a characteristically long hyoid bone, the long bone in chameleon's throats that they use to shoot their sticky tongues out at top speeds to capture unsuspecting prey.

These fossils can also offer other clues into the lizards' lives. Amber, because it is produced from tree resin, can only form in forested regions, so the animals must have been spending a lot of time around trees.

Amber can also preserve things when other processes cannot. The Myanmar forest amber is a good example because it's warm and moist in a tropical forest so things decompose quickly, Stanley explains. But something trapped in resin is not affected in the same way.

Amber is also good at preserving small things, like bits of plants, insects and other small animals, that might otherwise get lost in the fossil record. And it can preserve more of the organism, as it freezes it in place almost exactly how it lived, tissue and all.

How does it work? 

"It's a process of natural fixatives in the resin," George Poinar, an entomologist at Oregon State University known for his research on amber fossils who was not part of this study, tells the Monitor. "[The resin] contains preservatives that enter into the tissue," he explains. "At the same time, the sugars in the resin withdraw moisture from the specimen." Those two processes preserve the tissue of the organism as the amber hardens around it.

Dr. Poinar, who admits to having a "fertile imagination," was intrigued by the fact that although there were many different types of lizards frozen in time, many of the specimens were incomplete. He proposes that perhaps the lizards were stuck in the resin in a mad dash to escape a carnivorous dinosaur looking for a tasty morsel. 

In Poinar's scenario, vicious, agile, clawed dinosaurs chased the lizards up a tree. When the lizards became ensnared in resin, the hungry dinosaur would have snacked on them, leaving behind the parts that would mean also eating the sticky goop. 

"This is just speculation on my part," Poinar says. But, he adds, it could explain why so many of these lizards appear to be tree-dwellers while many of them live on the ground today.

You've read  of  free articles. Subscribe to continue.
Real news can be honest, hopeful, credible, constructive.
What is the Monitor difference? Tackling the tough headlines – with humanity. Listening to sources – with respect. Seeing the story that others are missing by reporting what so often gets overlooked: the values that connect us. That’s Monitor reporting – news that changes how you see the world.

Dear Reader,

About a year ago, I happened upon this statement about the Monitor in the Harvard Business Review – under the charming heading of “do things that don’t interest you”:

“Many things that end up” being meaningful, writes social scientist Joseph Grenny, “have come from conference workshops, articles, or online videos that began as a chore and ended with an insight. My work in Kenya, for example, was heavily influenced by a Christian Science Monitor article I had forced myself to read 10 years earlier. Sometimes, we call things ‘boring’ simply because they lie outside the box we are currently in.”

If you were to come up with a punchline to a joke about the Monitor, that would probably be it. We’re seen as being global, fair, insightful, and perhaps a bit too earnest. We’re the bran muffin of journalism.

But you know what? We change lives. And I’m going to argue that we change lives precisely because we force open that too-small box that most human beings think they live in.

The Monitor is a peculiar little publication that’s hard for the world to figure out. We’re run by a church, but we’re not only for church members and we’re not about converting people. We’re known as being fair even as the world becomes as polarized as at any time since the newspaper’s founding in 1908.

We have a mission beyond circulation, we want to bridge divides. We’re about kicking down the door of thought everywhere and saying, “You are bigger and more capable than you realize. And we can prove it.”

If you’re looking for bran muffin journalism, you can subscribe to the Monitor for $15. You’ll get the Monitor Weekly magazine, the Monitor Daily email, and unlimited access to CSMonitor.com.

QR Code to These 12 lizards were trapped in amber for 99 million years
Read this article in
https://www.csmonitor.com/Science/2016/0305/These-12-lizards-were-trapped-in-amber-for-99-million-years
QR Code to Subscription page
Start your subscription today
https://www.csmonitor.com/subscribe