Here is the Abstract just published in the science journal Science:
Tetrapodophis amplectus, as this new discovery was named and literally means "four-legged snake" possessed (as the name states) four legs which ended in five relatively long digits.
The specimen was identified as being a juvenile and was very small, measuring just 200 mm (a little over 7.8") long. The forelimbs were only 10 mm (just over ⅓") long with feet measuring 5 mm in length and the hindlimbs and feet were slightly larger. Being a juvenile it is of course possible that it could have grown much larger.
The researchers think that it is unlikely that Tetrapodophis used its feet for walking but rather used them to help hold onto a partner while mating, or could have been used to grasp its prey (that it likely constricted), in that they were very specialized for grasping.
It is possible that hey could also have assisted them in burrowing. The low spines on the vertebrae and its tail is suggestive of it having descended from burrowing creatures.
The researchers were able to conclusively determine that Tetrapodophis was definitely a snake and not some other reptile. For instance, the fossil showed evidence that the creature possessed a single row of belly scales which is considered by many experts to be the signature feature of a snake and is still seen on snakes today.
The fossilized skeleton had several other classic snake features including an elongated body, and not a long tail, along with an extremely flexible vertebrae column and long braincase. Further, the direction of the teeth as well as the pattern of the teeth (which included fangs), short snout and the bones of the mandible that was flexible allowing it to swallow large prey are all snake-like.
Jacques Gauthier of the Peabody Museum of Natural History at Yale University, who was not involved with the study, also points to "the bony supports in the pelvis for lymph hearts to pump blood back to the heart" as being "consistent with being a snake."
Interestingly, the fossilized snake also had the remains of its last meal still preserved in its stomach, including some bone fragments that the researchers think probably were from a salamander. Regardless of what its prey was this reveals that snakes were carnivorous much earlier in their history than had previously been thought.
So now we can now add the 120 myo (Early Cretaceous) snake from northeastern Brazil to several other examples of transitional snakes that only possessed two legs and are from later time periods. In fact the lead author, David M. Martill of the School of Earth and Environmental Sciences at the University of Portsmouth in the U.K., said that Tetrapodophis is "about 20 million years older than any other fossil snake."
For instance, in 2012 more fossilized material was discovered for a snake that researchers previously only knew from a few vertebrae. This snake Coniophis precedens lived roughly 70 mya (Late Cretaceous) in what is now eastern Wyoming and Montana.
Its physique indicates that Coniophis lived by burrowing and was not very big (70cm or a little over 2' long). Coniophis is a transitional snake in that it possessed a snake-like body and a lizard-like head. Further, the shape of the skull is intermediate between that of the lizards and snakes seen today as well. Hence we have an excellent example of a transitional between lizards and modern snakes.
In contrast with snakes around today in Coniophis the maxilla is firmly fixed to the skull meaning that its jaws remained fixed which limited the size of its prey. Fully evolved snakes have a kinetic skull with jaws that unhinge, allowing many species to eat prey larger than themselves. Also, the maxilla dominated the premaxilla unlike any other known snake.
IOW, it moved like a snake but didn't eat like one.
While the jaw was more like that found in other lizards, the shape of the teeth (tall, slim, cylindrical and curved backward) and their implantation (sit in shallow pits, bounded by bone ridges) are snake-like.
Coniophis wasn't venomous and all indications point to that particular trait evolving after the end of the Cretaceous.
So all this means that following the evolution of a serpentine body and carnivory, snakes evolved a highly specialized, kinetic skull. This provided them with a competitive advantage that contributed to a major adaptive radiation in the Early Cretaceous and eventually led to their becoming the most diverse lizard group today.
It should be noted that while Coniophis is the most primitive snake known it isn't the oldest. It was probably what is called a "living fossil" in its day.
Several older snakes reveal that they evolved from lizards with legs.
A number of ancient extinct snakes from the Mid Cretaceous such as Eupodophis, Pachyrhachis and Haasiophis had hind limbs. The fossilized remains of the hind limb on Eupodophis descouensi can clearly be seen here. The other two are supposed to have even more prominent legs (with some of the bones from the feet of Haasiophis being recovered).
There was also Najash rionegrina, which is slightly older though still from the Mid Cretaceous, that possessed fully functional hip bones "and the robust backbone vertebrae and rear legs of the snake were adapted to a burrowing subterranean environment."
A couple photos:
Hat tip to inertia at CARM smiley hat tip.gif
Tetrapodophis amplectus, as this new discovery was named and literally means "four-legged snake" possessed (as the name states) four legs which ended in five relatively long digits.
The specimen was identified as being a juvenile and was very small, measuring just 200 mm (a little over 7.8") long. The forelimbs were only 10 mm (just over ⅓") long with feet measuring 5 mm in length and the hindlimbs and feet were slightly larger. Being a juvenile it is of course possible that it could have grown much larger.
The researchers think that it is unlikely that Tetrapodophis used its feet for walking but rather used them to help hold onto a partner while mating, or could have been used to grasp its prey (that it likely constricted), in that they were very specialized for grasping.
It is possible that hey could also have assisted them in burrowing. The low spines on the vertebrae and its tail is suggestive of it having descended from burrowing creatures.
The researchers were able to conclusively determine that Tetrapodophis was definitely a snake and not some other reptile. For instance, the fossil showed evidence that the creature possessed a single row of belly scales which is considered by many experts to be the signature feature of a snake and is still seen on snakes today.
The fossilized skeleton had several other classic snake features including an elongated body, and not a long tail, along with an extremely flexible vertebrae column and long braincase. Further, the direction of the teeth as well as the pattern of the teeth (which included fangs), short snout and the bones of the mandible that was flexible allowing it to swallow large prey are all snake-like.
Jacques Gauthier of the Peabody Museum of Natural History at Yale University, who was not involved with the study, also points to "the bony supports in the pelvis for lymph hearts to pump blood back to the heart" as being "consistent with being a snake."
Interestingly, the fossilized snake also had the remains of its last meal still preserved in its stomach, including some bone fragments that the researchers think probably were from a salamander. Regardless of what its prey was this reveals that snakes were carnivorous much earlier in their history than had previously been thought.
So now we can now add the 120 myo (Early Cretaceous) snake from northeastern Brazil to several other examples of transitional snakes that only possessed two legs and are from later time periods. In fact the lead author, David M. Martill of the School of Earth and Environmental Sciences at the University of Portsmouth in the U.K., said that Tetrapodophis is "about 20 million years older than any other fossil snake."
For instance, in 2012 more fossilized material was discovered for a snake that researchers previously only knew from a few vertebrae. This snake Coniophis precedens lived roughly 70 mya (Late Cretaceous) in what is now eastern Wyoming and Montana.
Its physique indicates that Coniophis lived by burrowing and was not very big (70cm or a little over 2' long). Coniophis is a transitional snake in that it possessed a snake-like body and a lizard-like head. Further, the shape of the skull is intermediate between that of the lizards and snakes seen today as well. Hence we have an excellent example of a transitional between lizards and modern snakes.
In contrast with snakes around today in Coniophis the maxilla is firmly fixed to the skull meaning that its jaws remained fixed which limited the size of its prey. Fully evolved snakes have a kinetic skull with jaws that unhinge, allowing many species to eat prey larger than themselves. Also, the maxilla dominated the premaxilla unlike any other known snake.
IOW, it moved like a snake but didn't eat like one.
While the jaw was more like that found in other lizards, the shape of the teeth (tall, slim, cylindrical and curved backward) and their implantation (sit in shallow pits, bounded by bone ridges) are snake-like.
Coniophis wasn't venomous and all indications point to that particular trait evolving after the end of the Cretaceous.
So all this means that following the evolution of a serpentine body and carnivory, snakes evolved a highly specialized, kinetic skull. This provided them with a competitive advantage that contributed to a major adaptive radiation in the Early Cretaceous and eventually led to their becoming the most diverse lizard group today.
It should be noted that while Coniophis is the most primitive snake known it isn't the oldest. It was probably what is called a "living fossil" in its day.
Several older snakes reveal that they evolved from lizards with legs.
A number of ancient extinct snakes from the Mid Cretaceous such as Eupodophis, Pachyrhachis and Haasiophis had hind limbs. The fossilized remains of the hind limb on Eupodophis descouensi can clearly be seen here. The other two are supposed to have even more prominent legs (with some of the bones from the feet of Haasiophis being recovered).
There was also Najash rionegrina, which is slightly older though still from the Mid Cretaceous, that possessed fully functional hip bones "and the robust backbone vertebrae and rear legs of the snake were adapted to a burrowing subterranean environment."
A couple photos:
Hat tip to inertia at CARM smiley hat tip.gif
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