On a very rare occasion, an extraordinary fossil was unearthed which gave an extraordinary glimpse into the evolution of a group of organisms.
This time, it was an ancient snake skull that was beautifully preserved with rear members, Najash Rionegrina. Our study of these fossils has been published in journals Progress of Science.
These new fossils and others help answer old questions about the origin of snakes, such as how they lost limbs and developed their highly specialized skulls.
Najash Rionegrina named after the biblical snake Nahash (Hebrew for snake), and the Province of Río Negro in Argentina, where fossils were found.
Fossils of Najash around 95 million years old, and was first described in Natural from the fragmentary skull and partial body skeleton which protects the hind limbs.
This rear limb fossil snake gathered a lot of media interest as he followed previous reports of sea snake fossils with hind limbs. What makes Najash What is unique is that it is a land snake that lives in the desert, not a water snake that lives in the sea.
In addition, the fossils were not compressed evenly by the weight of the sediments on it, so they were preserved in three dimensions, unlike sea snake fossils.
Unfortunately, the first description of Najash relying on a very fragmented skull. Snake evolutionists were left guessing what the head of this ancient animal looked like.
We know from their common anatomy that snakes evolved from lizards. We also know that the skull of a snake is the key to the success of highly specialized eating adaptations. New Najash Skull fossils will be very informative about the evolutionary patterns of snake skulls.
It was a hot day in February 2013 when Fernando Garberoglio, then an undergraduate paleontologist from the Universidad de Buenos Aires, made his first field visit to the La Buitrera Paleontology Area in northern Patagonia, Argentina.
With him are two paleontologists: Sebastián Apesteguía, from Universidad Maimónides, and Guillermo Rougier, from the University of Louisville.
Looking for vertebrate fossils is a patient, exhausting discovery. This requires you to be close to the ground, scan sand, gravel, rocks and sediments for bone markings. You must take each part, examine it carefully, place it and then repeat it, hour after hour.
At La Buitrera, you are scorched by the scorching sun, pelted with rain and frozen by the cold Andean winds.
On: Student Fernando Garberoglio and palaeontologist Sebastian Apesteguía carry out fieldwork in the Paleontology Area of La Buitrera in northern Patagonia, Argentina.
But it is all worth it. Especially when, as happened with Garberoglio, he finally took a pebble, only a few centimeters long, to find a small, old-fashioned, boned face staring at him.
"I found a snake's skull!"
Rougier asked to examine his own fossils and found that, to his surprise, Garberoglio was right – there he was, a preserved skull, nearly 95 million years old, 3D.
It's been 13 years since then Najash named, and seven years since Fernando's discovery. Today, a long hunt has resulted in a treasure trove of skulls and new skeletons Najash from a fossil-rich site at La Buitrera.
Evolution of the skull
A long-standing hypothesis is that snakes evolved from blind and hiding ancestors of lizards. A group of small snakes, such as worms, small mouths, known as scolecophidians, have long been considered the most primitive living snakes.
The new one Najash fossil material shows that the skull from the line of ancient snakes was not like a scolecophidian snake. As a replacement, Najash and its type has a large mouth with sharp teeth and several movable skull joints which are characteristic of most modern snakes.
However, they still retain some of the more typical skull lizard bone features.
In evolutionary terms, Najash tells us that snakes evolved towards the mobility of the skull needed to swallow large enough prey objects, characteristic of many modern snakes.
Important information is also stored in bone-by-bone details stored in these new fossils Najash. For example, for a very long time, bone-like trunks located behind the eyes of modern snakes – called jugal – were considered equivalent to the postorbital bones of their lizard ancestors.
The idea follows that jugal does not exist in all snakes, fossils and modern.
New skull Najash shows conclusively that this is not true. Bones under orbit in Najash has the same shape, position and connection as the L-shaped jugal from a more typical lizard.
This shows that the rootstock also lost through the evolution of snakes, leaving jugal like a root in modern snakes. This is the postorbital bone that has been lost, not jugal.
This is a new specimen Najash is an excellent example of the predictive power of science. Hypotheses such as the presence of jugal in snakes can be supported by the discovery of new data that fulfills these predictions. What happens as a result is that old hypotheses are falsified and new ones are verified.
In short, skull Najash tells us that ancestral snakes are very similar to some of their close lizards' relatives, like big-bodied lizards, big-headed like dragons. This is really far from the idea that snakes could have evolved from small, blind ancestors, like worms, with small mouths; no ancient snake fossils are known to resemble primitive and small-mouthed scolecophidians.
Michael Caldwell, Professor of Vertebrate Paleontology, University of Alberta and Alessandro Palci, Research Associate in Evolutionary Biology, Flinders University.
This article is republished from The Conversation under a Creative Commons license. Read the original article.