Early ancestor of lizards and snakes discovered in Argentina

A fossil from Argentina has unveiled a missing piece in the history of the evolution of lizards and snakes. The new species Taytalura alcoberi may be representative of the earliest common ancestor of lizards and the enigmatic tuatara, according to a study from Harvard University. 

Many colloquially call the Cenozoic, our current geological era, the “Age of Mammals.” And while mammals on land occupy a great many niches that were once occupied by reptiles, they still rank among the most speciose amniote clades. 

More than 11,000 reptile species live today, and lepidosaurs make up the majority of those species. Lepidosauria is the technical name for the group of animals comprised of snakes, lizards, and tuataras (deceptively lizard-like creatures found exclusively in New Zealand). 

Lepidosaurs diverged from Archosaurs (the other major group of reptiles that includes crocodiles, non-avian dinosaurs, and birds) about 260 million years ago. Gaps in the early fossil record for this group mean that our understanding of their evolution is patchy. 

Study lead author Dr. Ricardo N. Martínez of the Universidad Nacional de San Juan discovered the fossil in a locality that had already produced some of the earliest dinosaurs. The three dimensional fossil preserves fine detail. 

According to Dr. Martinez, the fossil also highlights the paleontological importance of the paleontological site of Ischigualasto Formation.

The researchers, including Dr. Gabriela Sobral, used computed tomography scans and Bayesian analysis to identify skeletal features and decipher where Taytalura falls on the reptile family tree. 

“Taytalura preserves a composition of features that we were not expecting to find in such an early fossil. For instance, it shows some features that we thought were exclusive for the tuatara group. On the other hand, it made us question how truly ‘primitive’ certain lizard features are, and it will make scientists reconsider several points in the evolution of this group,” said Dr. Sobral.

Other primitive lepidosaurs were previously unearthed in Europe. Taytalura’s discovery extends the geographic range of these animals. While larger, more charismatic megafauna often grab headlines, smaller organisms can help illustrate the complexity of ancient ecosystems. 

“There was a universe of fauna sneaking among bigger, clawed or hoofy paws,” said study co-author Dr. Sebastián Apesteguía. “Taytalura teaches us that we were missing important information by looking not only for bigger animals, but for also thinking that the origin of lizards occurred only in the Northern Hemisphere as evidence seemed to support until now.” 

The science of paleontology depends on the collection of new and interesting fossils. With Taytalura, scientists can continue to untangle the winding branches of the bushy, complicated tree of life. 

The study is published in the journal Nature.

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By Alex Ruger, Earth.com Staff Writer