An article published in the journal “Science Advances” reports the study of new fossils of a snake belonging to the species Najash rionegrina, which lived in the Cretaceous period, between 90 and 100 million years, in today’s Patagonia, Argentina. A team of researchers led by Fernando Garberoglio of the Fundación Azara at Universidad Maimónides in Buenos Aires, Argentina, subjected various fossils belonging to this species, which had well-developed limbs, to a high-resolution CT scan to obtain new information on the evolution of snakes.
Najash rionegrina was first described in 2006 based on a fossil discovered in 2003 in the Candeleros Formation, in the province of Rio Negro, in Patagonia. It was a snake that lived on land, an important factor because paleontologists discuss the evolution of snakes with some claiming that they evolved from marine animals while others claim that they evolved from land animals.
Other species of ancient snakes and even some modern snakes preserve vestiges of limbs but Najash rionegrina had working limbs with a basin connected to the spine and a sacrum. In short, it’s a really interesting species that has been studied more after the discovery of more fossils.
Fernando Garberoglio and some colleagues had already conducted a study on some elements of the evolution of snakes, published in February 2019 in the journal “Scientific Reports”, which also included Najash rionegrina. Those researchers, along with some others, later conducted the new research published in “Science Advances”.
The top image (Courtesy Garberoglio et al.) shows fossils of specimens found in the La Buitrera paleontological area, in particular skulls but also other bones, especially in the specimen classified as MPCA 564 (D). These are not crushed fossils and therefore well preserved in three dimensions.
By subjecting the fossils to a high-resolution CT scan, it was possible to create 3D reconstructions that allow to examine their anatomical characteristics in detail. Najash rionegrina has the most complete and best preserved skull in three dimensions among ancient snakes, an excellent discovery to understand the evolution of snake skull from the rigid one of lizards to the very flexible one typical of today’s snakes.
The presence of working limbs indicates that Najash rionegrina had characteristics that existed for millions of years. That type of snakes diversified into land and aquatic niches. This species could have a distant relationship with most of today’s snakes. If that’s true, it means that more studies and probably more discoveries are needed to reconstruct the history of snakes.
