Rewriting history: Oldest tree-climbing reptile on record discovered in NM
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Jun. 21—It's a story 305 million years in the making.
One that was hidden deep within the Cañon del Cobre in southeastern part of Rio Arriba County.
Its name is Eoscansor.
On Tuesday, the New Mexico Museum of Natural History and Science announced that a team of paleontologists, including several from the museum, uncovered a fossil from the oldest tree-climbing reptile on record.
"Once again a fossil discovery from New Mexico rewrites the paleontology textbooks," said Spencer G. Lucas, curator of paleontology at NMMNHS. "In this case, revealing a tiny, agile climber that is a previously unexpected inhabitant of the Pennsylvanian world."
The reptile was named Eoscansor, from the Greek roots eo ("dawn") and scansor ("climber").
Lucas said Eoscansor is a eupelycosaur, a group of extinct reptiles that includes the familiar sail-backed reptile Dimetrodon, which is often mistaken for a dinosaur.
Though, eupelycosaurs are more closely related to mammals than dinosaurs.
According to the report, 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. Eoscansor would have been a small, highly agile climber, and its discovery likely means that many more such climbing reptiles remain to be discovered.
The research from NMMNHS and Carnegie Museum of Natural History describing the 305-million-year-old fossil has been published in the scientific journal Annals of the Carnegie Museum.
According to the report, the history of tetrapod arboreality (living in trees) has been long discussed.
"This animal is a new genus and species of varanopid eupelycosaur ... To establish its scansoriality (climbing), we provide diverse osteological criteria based on a review of skeletal traits indicative of and consistent with scansoriality in living and extinct tetrapods, notably in lizards," the report stated. "The new varanopid is the oldest known scansorial tetrapod capable of grasping and contributes to the growing diversity and disparity of varanopid eupelycosaurs."
Lucas said the fossil was found in 2005.
"... but (the team) did not really prepare and study it until 2015. We knew what we had by 2019, then the pandemic derailed us," Lucas said.
Other members of the research team include NMMNHS Research Associates Larry F. Rinehart and Matthew D. Celeskey, along with the Carnegie Museum of Natural History's Curator Emeritus David S Berman and Collections Manager Amy C. Henrici.
The fossil is now a part of the NMMNHS collection.
