305 Million Year Old Fossil Is Oldest Known Tree Climbing Reptile

A new genus and a new species of varanopidae eupelycosaurus which lived during the Carboniferous Period – the oldest tree-climbing reptile on record – has been identified from an incomplete skeleton found in New Mexico, USA.

Restoration of Eoscansor cobrensis. Photo credit: Matt Celeskey.

Eoscansor cobrensis lived in what is now New Mexico during the Pennsylvanian Subperiod of the Carboniferous Period, about 305 million years ago.

He belonged to Varanopidaean extinct family of monitor lizard-like reptiles that may have filled a similar niche.

The ancient reptile was 24.5 cm (9.6 inches) tall and weighed 58.3 g.

Various aspects of its anatomy indicate that Eoscansor cobrensis was a climber, and possibly arboreal (living in trees).

“Once again, a New Mexico fossil find is rewriting the textbooks of paleontology,” said Dr Spencer Lucascurator of paleontology at the New Mexico Museum of Natural History and Science.

“In this case, revealing a nimble little climber who is a previously unexpected inhabitant of the Pennsylvanian world.”

Photograph of the Eoscansor cobrensis holotype, blocks A (right) and B (left).  Image credit: Lucas et al., doi: 10.2992/007.087.0301.

Photograph of the holotype of Eoscansor cobrensis, blocks A (right) and B (left). Image credit: Lucas et al., doi: 10.2992/007.087.0301.

The incomplete skeleton of Eoscansor cobrensis was recovered from Formation of El Cobre Canyon in the Cañon del Cobre of Rio Arriba County, New Mexico.

The fossil is preserved as part and counterpart on two blocks of rock, called Block A and Block B.

“The discovery of Eoscansor cobrensis is an important addition to New Mexico’s fossil record, which is already among the strongest in the country,” said Dr. Lucas and his colleagues.

“First of all, the discovery pushes our understanding of when reptiles first started climbing back by at least 15 million years, because previously the oldest known climbing reptile came from rocks around 290 million years old in Germany.”

“Furthermore, the find demonstrates that reptiles were much more diverse in anatomy and behavior during the Pennsylvanian subperiod than previously known.”

“Many anatomical features of the fossil skeleton, particularly the limbs, hands and feet, indicate that it almost certainly climbed trees.”

“Its teeth indicate it was a predator that probably ate insects,” they said.

Eoscansor cobrensis would have been a very agile little climber, and its discovery probably means that many other climbing reptiles remain to be discovered.

The teams paper was published in the journal Annals of the Carnegie Museum.


Spencer G. Lucas et al. 2022. A Scansorial Varanopid Eupelycosaur from the Pennsylvanian of New Mexico. Carnegie Annals Museum 87 (3), 167-205; doi: 10.2992/007.087.0301

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