In very rare cases, an exceptional fossil will emerge, providing an extraordinary insight into the evolution of a group of organisms.
This time it is a beautifully preserved skull of an ancient snake with hind legs, Najash rionegrina . Our study of this fossil was published in Science Advances .
These and other new fossils help answer long-standing questions about the origin of snakes, such as how they lost their limbs and developed their highly specialized skulls.
Najash rionegrina is named after the legged biblical snake Nahash (Hebrew for Snake) and the province of Rio Negro in Argentina, where fossils were discovered.
The fossils of Najash are about 95 million years old and were first described in . Nature from a fragmentary skull and partial body that retained robust hind legs.
This fossil hind limb has gained great media interest while following previous reports of fossil marine snakes with hind limbs. What made Najash unique was that it was a land snake living in the desert, not a water snake living in the ocean.
In addition, the fossils were not compressed flat according to the weight of the overburden sediments and were thus preserved in three dimensions, unlike fossil sea snakes.
Unfortunately, the first description Najash was based on a very fragmented skull. Scientists of serpentine evolution have been guessed what the head of these ancient animals might look like.
From their common anatomy, we know that snakes have evolved into snakes. We also know that the skulls of snakes were the key to their successful and highly specialized feed adaptations. The new Najash fossil skull would be very informative about the evolution of the skull skull development.
It was a hot day in February 2013 when Fernando Garberoglio, then a paleontology college student from the Universidad de Buenos Aires, took his first excursion to the paleontological area of La Buitrera in northern Patagonia, Argentina.
There were two paleontologists with him: Sebastián Apesteguía of Universidad Maimónides and Guillermo Rougier of the University of Louisville.
The search for fossil vertebrates is an act of patient discovery. It requires you to be close to the ground, scan for grain, stones, stones and sediments for signs of bone.
In La Buitrera you are scorched by a hot sun, dusted with rain and frozen by cold Andean winds.
Northern Patagonia, Argentina.
But it's all worth it. Especially when, as happened to Garberogli, he finally lifted a stone only a few centimeters long to find a small ancient bony face looking at him.
"I found a snake skull!"
Rougier asked to inspect the fossil himself and found to his surprise Garberoglio was right – it was an almost complete, 95 million years old, 3D preserved snake skull
It's been 13 years since Najash and 7 years since the discovery of Fernando. Today's long hunt today brought a reward for the treasure of new skulls and skeletons Najash from fossil sites in La Buitrera.
A long-term hypothesis is that snakes have developed from a blind previous lizard. A group of small, worm-like, tiny burrowing snakes, known as greaves, have long been considered the most primitive living snakes.
The new Najash fossil material shows that the skulls of this line of ancient snakes were nothing like sclerophidian snakes. Instead, Najash and his species had a large mouth with sharp teeth and some of the moving skull joints that are typical of the most modern snakes. However, they still retain some features of skeletal skulls of more typical lizards.
From an evolutionary point of view Najash says that snakes have evolved towards the cranial mobility needed to swallow relatively large items that are prey, a hallmark of many modern snakes. flirting samples of snakes ” width=”700″ style=”width: 100%;”/> Najash samples from LBPA. (Flinders University)
Critical information is also stored in the details of the bones preserved in these new Najash fossils . For example, for a very long time, the rod bone located behind the eye of modern snakes – called jugal – was considered equivalent to the post-orbital bone of their lizard ancestors.
The idea followed that jugal was not present in all snakes, fossil and modern.
The new Najash skull convincingly shows that this is not correct. The bone under the orbit in Najash has the same shape, position and connection as the L.-shaped more typical lizards.
This proves that the lower jugala rod has been lost as a result of the development of snakes, leaving in the modern snakes a rod like jugal. Post-orbital bone lost, not jugal.
These new specimens of Najashu (19459005) are an excellent example of the predictive power of science. Hypotheses such as the presence of Portuguese snakes may be supported by the discovery of new data that meet these predictions. As a result, the old hypothesis is falsified and the new hypothesis is proven.
In short, the skull of Najash tells us that the ancestor snakes were very similar to some of their close relatives of the lizards. , such as lizards with large bodies and heads, such as Komodo dragons. This is indeed far from the idea that snakes could evolve from small, blind, worm-like ancestors with small mouths; no known fossils of ancient snakes at all resemble allegedly primitive leper scolecophidians with small mouths.
Michael Caldwell, professor of vertebrate paleontology, University of Alberta and Alessandro Palci, researcher at Evolutionary Biology, Flinders University.
This article is republished from a conversation under a Creative Commons license. Read the original article.