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This fossil find of the ancient “Snake with Feet” tells an incredible story.

In very rare cases, an exceptional fossil is found, which gives an extraordinary look at the evolution of a group of organisms.

This time it’s a perfectly preserved skull of an ancient snake with hind limbs, Najash RionegrinaOur study of this fossil was published in the journal Scientific achievements,

This and other new fossils help answer long-standing questions about the origin of snakes, for example, how they lost their limbs and developed their highly specialized skulls.

Fossil story

Najash Rionegrina named after the biblical snake on the feet of Nahash (Hebrew for the snake) and the Rio Negro province in Argentina, where fossils were discovered.

Fossils Najash about 95 million years, and were first described in Nature from a fragmented skull and partial skeleton of the body, which retained strong hind limbs.

Naj snake artist impressionExecution of the artist Nadzhash snake. (Raul O. Gomez, University of Buenos Aires, Buenos Aires, Argentina)

This fossil snake with hind limbs aroused great interest among the media as it followed earlier reports of fossil sea snakes with hind limbs. What did Najash unique was that it was an earth snake living in the desert, and not a water snake living in the ocean.

In addition, the fossils were not compressed flat due to the weight of the overlying deposits, and therefore they were preserved in three dimensions, unlike fossilized sea snakes.

Unfortunately, this is the first description Najash leaned on a very ragged skull. The scientists of the evolution of snakes had to guess how the head of these ancient animals could look.

From their general anatomy, we know that snakes came from lizards. We also know that snake skulls were the key to their successful and highly specialized adaptation to feeding. new Najash Petrified skulls would be very informative about the nature of the evolution of the snake's skull.

New discovery

It was a hot day in February 2013 when Fernando Garberoglio, the then student paleontologist at the University of Buenos Aires, went on his first field trip to the La Buitrera paleontological area in northern Patagonia, Argentina.

He was accompanied by two paleontologists: Sebastian Apestegia from the University of Maimonides and Guillermo Shotgun from the University of Louisville.

The search for vertebrate fossils is the patient’s business, a painstaking discovery. This requires you to be close to the ground, looking at sand, pebbles, stones and deposits for bones. You have to pick up each piece, carefully examine it, lower it and then repeat hour after hour.

In La Buitrera you are scorched by the hot sun, covered in torrential rain and frozen by the cold Andean winds.

file 20191119 169374 1ujq53m(Fernando Garberoglio)

Above: Student Fernando Garberoglio and paleontologist Sebastian Apestegia carry out field work in the La Buitrera paleontological area in northern Patagonia, Argentina.

But it's worth it. Especially when, as happened with Garberoglio, he finally lifted a pebble just a few centimeters long and found a small, ancient, bony face staring at him.

"I found a snake skull!"

The shotgun asked himself to examine the fossil and found that, to his surprise, Garberoglio was right – it was an almost complete, 95-year-old, 3D-preserved skull of a snake.

13 years have passed since then Najash was named, and seven years after the discovery of Fernando. Today, a long hunt brought a reward for the treasury of new skulls and skeletons Najash from fossil rich sites in La Buitrera.

Skull evolution

A long-held hypothesis is that snakes came from a blind, digging ancestor of a lizard. A group of small, worm-like, digging snakes with a small mouth, known as the scolecophidians, have long been considered the most primitive living snake.

New Najash Fossil materials show that the skulls of that line of ancient snakes had nothing to do with the skulls of the Scolecophidian snakes. Instead, Najash and his species had large mouths with sharp teeth and some movable skull joints, which are typical of most modern snakes.

However, they still retain some features of the bony skull of more typical lizards.

In evolutionary terms Najash tells us that snakes evolved in the direction of skull mobility needed to absorb fairly large prey items, which is a feature of many modern snakes.

snake snake samplesNadyash instances from LBPA. (Flinders University)

Scientific forecast

Critical information is also stored in bone details stored in these new fossils. NajashFor example, for a very long time, the rod-shaped bone located behind the eye of modern snakes, called the yugal, was considered the equivalent of the postorbital bone of their lizard ancestors.

The idea was that jugal was absent from all snakes, fossils and modern ones.

New skull Najash convincingly demonstrates that this is not correct. Bone below orbit in Najash has the same shape, position and connection as the L-shaped yugal of more typical lizards.

This demonstrates that the lower strip of the vessel was lost as a result of the evolution of the snake, leaving behind it like a jugal stick in modern snakes. This is a lost postorbital bone, not a yugal.

These new designs Najash are a great example of the predictive power of science. Hypotheses, such as the presence of jugal in snakes, can be confirmed by the discovery of new data that are consistent with these predictions. As a result, it turns out that the old hypothesis is falsified, and the new one is verified.

In short, the skull Najash tells us that the family snakes were very similar to some of their close lizard relatives, such as lizards with large bodies and large heads, such as Komodo dragons. It is indeed far from the idea that snakes could evolve from tiny, blind, worm-shaped, with small mouths of their ancestors; no known fossils of ancient snakes resemble supposedly primitive scolecophidians with a small mouth.Conversation

Michael Caldwell, Professor of Vertebrate Paleontology, University of Alberta and Alessandro Palchi, Research Fellow in Evolutionary Biology, Flinders University.

This article has been reprinted from The Conversation under a Creative Commons license. Read the original article.

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