Fossil of oldest known species of tree-climbing reptile discovered in Northern New Mexico

June 21st, 2022

Albuquerque, NM - A team of paleontologists, including several from New Mexico Museum of Natural History and Science (NMMNHS), have uncovered a fossil in New Mexico from the oldest tree-climbing reptile on record. 

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. The new fossil was found in Northern New Mexico near Chama, in 305-million-year-old rocks from the Pennsylvanian Period of Earth’s history. The fossil is now a part of the NMMNHS collection. 

“Once again a fossil discovery from New Mexico rewrites the paleontology textbooks,” said Dr. 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.” 

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 Dr. David S Berman and Collections Manager Amy C. Henrici. 

The newly discovered reptile was named Eoscansor (EE-oh-SKAN-sor), from the Greek roots eo (“dawn”) and scansor (“climber”). Eoscansor is a eupelycosaur, a group of extinct reptiles that includes the familiar sail-backed reptile Dimetrodon, which is often mistaken for a dinosaur. However, eupelycosaurs are more closely related to mammals than dinosaurs. 

The discovery is a significant addition to New Mexico’s fossil record, which is already among the most robust in the nation. Firstly, the discovery of Eoscansor 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 Period 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. Eoscansor would have been a small, highly agile climber, and its discovery likely means that many more such climbing reptiles remain to be discovered. 

About the New Mexico Museum of Natural History and Science The New Mexico Museum of Natural History and Science is a division of the Department of Cultural Affairs, under the leadership of the Board of Trustees of the New Mexico Museum of Natural History & Science. Programs and exhibits are generously supported by the New Mexico Museum of Natural History Foundation, through the generous support of donors. Established in 1986, the mission of the New Mexico Museum of Natural History & Science is to preserve and interpret the distinctive natural and scientific heritage of our state through extraordinary collections, research, exhibits, and programs designed to ignite a passion for lifelong learning. The NMMNHS offers exhibitions, programs, and workshops in Geoscience, including Paleontology and Mineralogy, Bioscience, and Space Science. It is the Southwest’s largest repository for fossils and includes a Planetarium and a large format 3D DynaTheater.