The tiny skeleton of a baby chameleon, trapped in amber, has been identified as the oldest chameleon ever found. Dating back 99 million years, to the Cretaceous Period, it is older than the previous record holder by some 78 million years.
The 18-millimetre (0.7in) specimen was one of 12 lizard specimens trapped in amber donated to the American Museum of Natural History by a private collector. Three of these, a gecko, an ancient lizard and the chameleon, originating from tropical jungles in what is now Myanmar, were in excellent condition. A paper on them has been published in the journal Science Advances.
This was a remarkable find in its own right.
"These fossils tell us a lot about the extraordinary, but previously unknown diversity of lizards in ancient tropical forests," study co-author Edward Stanley of the University of Florida, who analysed the specimens, said in a statement.
"The fossil record is sparse because the delicate skin and fragile bones of small lizards do not usually preserve, especially in the tropics, which makes the new amber fossils an incredibly rare and unique window into a critical period of diversification."
To date and study the lizards, the team used a micro-CT scanner to capture a full 3D scan of the skeletons without having to cut into the amber. They were then able to digitally reconstruct models of the skeletons and create 3D prints to learn more about the animals' physiologies.
"It was mind-blowing," Stanley said. "Usually we have a foot or other small part preserved in amber, but these are whole specimens -- claws, toepads, teeth, even perfectly intact coloured scales. I was familiar with CT technology, so I realized this was an opportunity to look more closely and put the lizards into evolutionary perspective."
The gecko's remains indicated that geckos already had adhesive toepads, which suggests they had developed this trait earlier than thought.
The chameleon revealed some new information too. By examining the bones in the chameleon's head, the team was able to determine that its tongue, like the tongues of modern chameleons, flicks out at high speed to capture prey. However, it had not yet developed the fused toes or body shape of modern chameleons.
Moreover, its existence challenges the notion that chameleons originated in Africa, as had been thought. This gives the researchers important clues about where these reptiles fit on the tree of life, and where they can look for more. They also highlight the importance of conservation efforts.
"These exquisitely preserved examples of past diversity show us why we should be protecting these areas where their modern relatives live today," Stanley said.
"The tropics often act as a stable refuge where biodiversity tends to accumulate, while other places are more variable in terms of climate and species. However, the tropics are not impervious to human efforts to destroy them."