A new genus and species of varanopid eupelycosaur that lived during the Carboniferous period — the oldest tree-climbing reptile on record — has been identified from an incomplete skeleton found in New Mexico, the United States.
Eoscansor cobrensis lived in what is now New Mexico during the Pennsylvanian subperiod of the Carboniferous period, some 305 million years ago.
It belonged to Varanopidae, an extinct family of reptiles that resembled monitor lizards and may have filled a similar niche.
The ancient reptile measured 24.5 cm (9.6 inches) and weighed 58.3 g.
Diverse aspects of its anatomy indicate that Eoscansor cobrensis was a climber, and possibly arboreal (living in trees).
“Once again a fossil discovery from New Mexico rewrites the paleontology textbooks,” said Dr. Spencer Lucas, curator of paleontology at the New Mexico Museum of Natural History and Science.
“In this case, revealing a tiny, agile climber that is a previously unexpected inhabitant of the Pennsylvanian world.”
The incomplete skeleton of Eoscansor cobrensis was recovered from the El Cobre Canyon Formation in the Cañon del Cobre of Rio Arriba County, New Mexico.
The fossil is preserved as part and counterpart on two blocks of rock, referred to as block A and block B.
“The discovery of Eoscansor cobrensis is a significant addition to New Mexico’s fossil record, which is already among the most robust in the nation,” Dr. Lucas and colleagues said.
“Firstly, the discovery pushes back our understanding of when reptiles began climbing by at least 15 million years, as previously the oldest known climbing reptile was from approximately 290-million-year-old rocks in Germany.”
“Additionally, the discovery demonstrates that reptiles were much more diverse in anatomy and behavior during the Pennsylvanian subperiod than was previously known.”
“Many anatomical features from the fossil skeleton, especially the limbs, hands, and feet, indicate that it almost certainly climbed trees.”
“Its teeth indicate it was a predator that likely ate insects,” they said.
“Eoscansor cobrensis would have been a small, highly agile climber, and its discovery likely means that many more such climbing reptiles remain to be discovered.”
The team’s 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. Annals of Carnegie Museum 87 (3), 167-205; doi: 10.2992/007.087.0301
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