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Ancient lizards in amber amaze scientists

Lizards of the Caribbean A community of lizards from the Caribbean, preserved for 20 million years in amber, have been found to be identical to their modern cousins, say researchers.

This suggests the different niches inhabited by the lizards have - incredibly - changed little over the past 20 million-year, report the team, in this week's Proceedings of the National Academy of Sciences.

"These fossils were really surprising because of how much detail they contained, allowing us to see how these lizards would have looked in real life," says the study's lead author Dr Emma Sherratt of the University of New England in Australia.

Sherratt says amber fossils are usually just a hollow impression, but the new fossils of anolis lizards from the island of Hispaniola, provide phenomenal detail -- including the colour of the lizard, what it was last doing, and whether its eyes were open or shut.

"Most of ours had full skeletons, and details of the skin were impressed on the amber, providing very detailed images of tiny scales on the body and on the sticky toe pads," she adds.

"You could have taken a lizard today, embedded it resin and it would have looked like one of these creatures. That's how realistic and modern they look."

Another impressive aspect to the study is the large number of amber fossils analysed.

While previous research has mostly looked at individual specimens, this study involved 38 lizards fossils from various locations on Hispaniola.

Obtain from museums and private collections -- one was even a pendant in a necklace -- the community of fossils represent the largest group of vertebrates encased in amber.

"Nothing like this has ever been described before," says Sherratt.

Evolutionary models

There are over 400 species of anolis lizards spread across the islands of the Caribbean, with each species adapting to a specific ecological niche.

Earlier DNA studies indicated anolis lizards began colonising the Caribbean about 40 million years ago, quickly diversifying into different niches such as the forest canopy, tree branches, main trunks, leaf litter on the forest floor, or grasslands.

As different groups began occupying different niches, their body shapes, leg length, and the little scales on their toe pads that help them climb like geckos, changed accordingly to suit each niche.

Using x-ray microcomputer tomography to produce three dimensional reconstructions of the fossils inside their amber cocoons, the researchers showed that the diversity of lizards that resulted 20 million years ago is the same seen today.

"Given we see the same range of morphological features this means the community of lizards has remained unchanged all this time," says Sherratt.

Steady niches

Sherratt says it is "very striking" that the lizards don't seem to have changed at all during this long period, during, over which all the main animal types evolved.

"Evidence of anolis lizards living unchanged in different niches for 20 million years, indicates these niches have been stable for that period of time," she says.

"That's quite surprising because these lizards have gone to other islands and over to the Florida mainland where they seem to evolve very rapidly. So it's not that they don't have the propensity to change, it's just that the structure of the environment has been stable enough that they haven't needed to change in 20 million years."

Available evidence suggests that ecological communities change rapidly over the short term, says Sherratt.

However, she says, the findings are among the first to look at long term stability of ecological communities, and show that niches and the communities they support can remain stable over millions of years.