Oldest species of tree-climbing reptile found in New Mexico

A tiny lizard has made its first climb up a tree in what was once an island rainforest in New Mexico.

It was a climb that, hundreds of millions of years later, would dramatically alter what was known about reptile evolution.

After this lizard died, it was fossilized in the dirt and soil of this forest, the ocean dried up and left behind the arid, mountainous desert now known to define the landscape of northern New -Mexico.

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Named Eoscansor by the scientists who discovered it – from the Greek roots “eo” for dawn and “scansor” for mountaineer – the reptile was found among exposed rocks near Chama, along the border of New -Mexico with Colorado.

The fossil was excavated from rocks that are 305 million years old, about 15 million years older than the oldest known tree-climbing reptile in Germany.

This has significantly delayed the timeline of reptilian evolution, said Professor PHD Spencer Lucas, curator of geology and paleontology at the New Mexico Museum of Natural History and Science.

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“This sets a new benchmark in reptile history,” Lucas said. “The tree climbing is not an easy thing to do. This sets it back 15 million years. This probably means there are older tree climbers.

Lucas led a team of paleontologists from the New Mexico Museum and the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania, who discovered the fossil, among other places, in 2005 amid canyons and exposed rocks in the area.

A fossil of Ecoscansor, the oldest known tree-climbing reptile discovered in New Mexico.

He said the age of the fossil and its small size, just a few centimeters long, made it particularly difficult to extract from rock and prepare for study.

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“We were looking for fossils in rocks that were 300 to 305 million years old,” Lucas said. “It’s about 80% of the skeleton of a very small animal. It took years to prepare. We had many more that we were working on. I call it a slow burn.

“We came to this little guy at the end of the project because he was so hard to prepare off the rock.”

Despite its small size, Lucas said the growth and development of Eoscansor was an important evolutionary moment.

He said such large events often occur in smaller animals discovered in smaller fossils.

Larger animals, Lucas said, frequently develop at the end of evolutionary chains.

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“A lot of people are very interested in large fossils, but we know that the biggest evolutionary events happen in small animals,” he said. “This animal is quite remarkable. It is the oldest known tree-climbing reptile.

“It’s a really rare event. If you look at other fossils from this period, no one seems to be climbing trees.

A rendering of the skeleton of Ecoscansor, the oldest known tree-climbing reptile discovered in New Mexico.

Researchers believed the animal was a tree climber, Lucas said, based on the design of its feet which appeared adept at moving on branches and its location in an area believed to have once been forest. islander.

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This ecosystem generally prevents animals from becoming fossilized as their carcasses are usually eaten by other animals in the densely populated forest.

“New Mexico was a very tropical, humid and hot place. There were shallow seas,” Lucas said.

“We know that animals that live in a rainforest have a very low chance of entering the fossil record. When animals in a rainforest die, the body falls to the ground and they are usually consumed completely before being consumed. buried.

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Preparatory work was recently completed and the find was published in June by the journal Annals of the Carnegie Museum.

The fossil has been added to the museum’s collection and continues a legacy of discoveries in New Mexico, said Gary Romero, acting director of the New Mexico Museum of Natural History and Science (NMMNHS).

“This discovery not only adds to our understanding of early reptile development, it also strengthens the New Mexico Museum of Natural History and Science as a powerhouse of paleontology,” Romero said.

“New Mexico is a fossil hotspot, and research conducted by our dynamic paleoscience department means that NMMNHS is well positioned to take advantage of our unique natural setting.”

Adrian Hedden can be reached at 575-628-5516, [email protected] or @AdrianHedden on Twitter.

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