The Evolution Of Snakes

[Mighty_Emperor]

NOTE: A paper describing this research will be published in the 7 May 2004 issue of Biology Letters, a journal published by the Royal Society in the United Kingdom. See end of press release for preprints, photos, and contacts.

Scientists Discover Where Snakes Lived When They Evolved into Limbless Creatures

30 January 2004 --The mystery of where Earth's first snakes lived as they were evolving into limbless creatures from their lizard ancestors has intrigued scientists for centuries. Now, the first study ever to analyze genes from all the living families of lizards has revealed that snakes made their debut on the land, not in the ocean. The discovery resolves a long-smoldering debate among biologists about whether snakes had a terrestrial or a marine origin roughly 150 million years ago--a debate rekindled recently by controversial research in favor of the marine hypothesis.

In a paper to be published in the 7 May 2004 issue of the Royal Society journal Biology Letters, Nicolas Vidal, a postdoctoral fellow, and S. Blair Hedges, a professor of biology at Penn State, describe how they put the two theories to the test. They collected the largest genetic data set for snakes and lizards ever used to address this question. Their collection includes two genes from 64 species representing all 19 families of living lizards and 17 of the 25 families of living snakes.

Genetic material from some of the lizards was difficult to obtain because some species live only on certain small islands or in remote parts of the world. "We felt it was important to analyze genes from all the lizard groups because almost every lizard family has been suggested as being the one most closely related to snakes. If we had failed to include genes from even one of the lizard families, we could have missed getting the right answer," Hedges explains.

"For the marine hypothesis to be correct, snakes must be the closest relative of the only lizards known to have lived in the ocean when snakes evolved—the giant, extinct mosasaur lizards," Vidal says. "While we can't analyze the genes of the extinct mosasaurs, we can use the genes of their closest living cousins, monitor lizards like the giant Komodo Dragon," he explains.

The team analyzed gene sequences from each of the species, using several statistical methods to determine how the species are related. "Although these genes have the same function in each species—and so, by definition, are the same gene—their structure in each species is slightly different because of mutations that have developed over time," Vidal explains. When the genetic comparisons were complete, Vidal and Hedges had a family tree showing the relationships of the species.

"Our results show clearly that snakes are not closely related to monitor lizards like the giant Komodo Dragon, which are the
closest living relatives of the mosasaurs—the only known marine lizard living at the time that snakes evolved," Vidal says. "Because all the other lizards at that time lived on the land, our study provides strong evidence that snakes evolved on the land, not in the ocean."

The research suggests an answer to another long-debated question: why snakes lost their limbs. Their land-based lifestyle, including burrowing underground at least some of the time, may be the reason.

"Having limbs is a real problem if you need to fit through small openings underground, as anybody who has tried exploring in caves knows," Hedges says. "Your body could fit through much smaller openings if you did not have the wide shoulders and pelvis that support your limbs." The researchers note that the burrowing lifestyle of many other species, including legless lizards, is correlated with the complete loss of limbs or the evolution of very small limbs.

http://www.science.psu.edu/alert/Hedges1-2004.htm

 

[Comfortably Numb]

New Fossils of Ancient Snake With Hind Legs Reveals Tantalizing Details of Evolution

New fossils of an ancient legged snake, called Najash, shed light on the origin of the slithering reptiles, including how snakes got their bite and lost their legs.

The fossil discoveries published in Science Advances have revealed they possessed hind legs during the first 70 million years of their evolution.

They also provide details about how the flexible skull of snakes evolved from their lizard ancestors.

The evolution of the snake body has captivated researchers for a long time — representing one of the most dramatic examples of the vertebrate body’s ability to adapt — but a limited fossil record has obscured our understanding of their early evolution until now.

https://scitechdaily-com.cdn.amppro...3A%2F%2Fwww.google.com&amp_tf=From%20%251%24s

 

[EnolaGaia]

A fossil reptile recently discovered and touted as an intermediate species in the evolution of legless snakes is now claimed to be something else entirely.

Famous Discovery of Four-Legged Snake Fossil Turns Out to Have a Twist in The Tale

In 2015, paleontologists announced a stunning discovery. Preserved in Cretaceous rock from Brazil was the complete skeleton of a beast resembling a snake, but with one significant addition: four tiny, almost vestigial legs.

This marked something of a paleontological 'holy grail'. The beast, which they named Tetrapodophis amplectus, was the missing link between snakes and lizards.

There's just one problem. According to a new analysis of the remains, Tetrapodophis (from the Greek, meaning "four-legged snake") is not a snake at all, but a species of extinct marine lizard that lived over 110 million years ago.

"There are many evolutionary questions that could be answered by finding a four-legged snake fossil, but only if it is the real deal," says paleontologist Michael Caldwell of the University of Alberta in Canada.

"The major conclusion of our team is that Tetrapodophis amplectus is not in fact a snake and was misclassified. Rather, all aspects of its anatomy are consistent with the anatomy observed in a group of extinct marine lizards from the Cretaceous period known as dolichosaurs." ...

FULL STORY: https://www.sciencealert.com/this-famous-four-legged-snake-fossil-is-something-else-after-all