On very rare occasions, an exceptional fossil is discovered that provides an excellent overview of the evolution of a group of organisms.
This time, it's a beautifully preserved ancient limb-snake skull, Najash rionegrina. Our study of this fossil is published in the journal Advances in science.
This and other new fossils help answer longstanding questions about the origin of snakes, such as how they lost limbs and developed their specialized skulls.
Najash rionegrina it is named after the foot-snake bible Nachash (Hebrew for snake), and the province of Rio Negro in Argentina, where the fossils were discovered.
Fossils from Find out are about 95 million years old and were first described in Nature from a fragmentary skull and partial skeleton of the body that preserved robust hind limbs.
This rear extreme fossil snake has garnered much interest in the media, as earlier reporting of fossil sea snakes with hind limbs followed. What did you do Find out what was 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 by the weight of the overlying sediments, and so they were preserved in three dimensions, unlike the fossil sea snakes.
Unfortunately, that first description of Find out relied on a very fragmented skull. Scientists on the evolution of snakes have left to guess what the head of these ancient animals looked like.
From their common anatomy we know that snakes evolved from lizards. We also know that snake skulls are key to their successful and highly specialized feeding arrangements. New Find out fossil skulls would be very informative about the evolution pattern of the snake skull.
The new discovery
It was a hot day in February 2013 when Fernando Garberoglio, then an undergraduate paleontology student from Universidad de Buenos Aires, departed on his first field trip to the La Buitreera Paleontological Area in northern Patagonia, Argentina.
With him were two paleontologists: Sebastian Apestegusa of the Universidad Maiminid and Guillermo Rougier of the University of Louisville.
Searching for fossil vertebrae is an act of patient, painstaking discovery. You need to be close to the ground, scanning your bones, pebbles, rocks and bones. You have to pick up each piece, check it closely, lower it and then repeat it, hour after hour.
At La Bouitrera, you are burned by the scorching sun, burned by rain and frozen by the cold Andesian winds.
Upstairs: Student Fernando Garberoglio and paleontologist Sebastian Apestegusa conduct fieldwork at the La Buiterra Paleontological District in northern Patagonia, Argentina.
But it is all worth it. Especially when, as with Garberoglio, he finally picks up a pebble, just a few centimeters long, to find a small, ancient, bony face staring at him.
"I found a snake skull!"
Rougier asked to check the fossil itself and found that, to his surprise, Garberlio was right – there was, almost complete, a 95 million-year-old, snake-skull preserved.
13 years have passed Find out was named seven years after the discovery of Fernando. Today, the long hunt brings its treasure trove of new skulls and skeletons from Find out from the fossil-rich places in La Buitra.
Evolution of the skull
The long-held hypothesis is that snakes evolved from a blind, buried lizard ancestor. A group of small, worm-like, small shag snakes, known as shellfish, have long been considered the most primitive living snakes.
New Find out fossil materials show that the skulls of that ancient snake lineage were nothing like those of the olecus snakes. Instead of, Find out and of this kind there were large mouths with sharp teeth and some movable skull joints typical of most modern snakes.
However, they still retained some of the features of bone skulls of more typical lizards.
In an evolutionary sense, Find out tells us that snakes evolved to the mobility of the skull, necessary to bring in fairly large preys, a feature of many modern snakes.
Critical information is also preserved in the bone-bone details preserved in these new fossils from Find out. For example, for a very long time, the bony-like bone behind the eyes of modern snakes – called the jagagal – was thought to be the equivalent of the postbiblical bone of their ancestral lizard.
The idea was that the yug was absent in all snakes, fossil and modern.
The new skull of Find out demonstrates convincingly that this is not true. Bone under orbit in Find out has the same shape, position, and connections as the L-shaped yogurt of more typical lizards.
This indicates that the lower part of the south was lost during the evolution of the snakes, leaving behind a rod-like jug of modern snakes. It is the lost postbital bone, not the Jugans.
These new samples of Find out are an excellent example of the predictive power of science. Hypotheses such as the presence of Yuga in snakes can be supported by the discovery of new data that meet these predictions. What happens as a result is that the old hypothesis is forged and a new one is confirmed.
In short, the skull of Find out tells us that the ancestors of snakes were very similar to some of their close relatives to lizards, such as large lizards to large lizards like the Komodo dragons. This is really far from the idea that snakes could evolve from tiny, blind, worm-like, tiny ancestors; no known ancient snake fossil resembles any supposedly primitive, small shellfish.
Michael Caldwell, Professor of Vertebrate Paleontology, University of Alberta and Alessandro Palci, Research Associate in Evolutionary Biology, Flinders University.
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