Ancient Snakes Had Limbs for 70 Million Years: Study
Wed, April 21, 2021

Ancient Snakes Had Limbs for 70 Million Years: Study

Snakes are incredibly diverse creatures. They are found in many different habitats such as land, water, and even trees / Photo by: Kurit afshen via Shutterstock

 

Snakes are incredibly diverse creatures. They are found in many different habitats such as land, water, and even trees. They are one of the more than 3,400 species of reptiles that have a greatly elongated body and tail, and limbless condition. However, snakes are also one of the most misunderstood creatures in the animal kingdom. The misconceptions about them are primarily out of ignorance about their true nature and position in the natural world. While we see them as venomous reptiles, studies show that fewer than 300 species are venomous.

Part of the increasing misconceptions about snakes is that their evolution has been such an enduring mystery for scientists. This is because the vast majority of their populations are small and relatively fragile. While paleontologists have discovered snake fossils dating as far back as 150 million years, the traces have quickly faded and are considered practically useless. 

But just like other animals, snake evolution has undergone structural reduction, simplification, and loss. One of the most significant discoveries is that prehistoric snakes have attained gigantic sizes, although fossil evidence can be frustratingly inconclusive. Gigantophis, the biggest prehistoric snake in fossil records, measured about 33 feet from head to tail and weighed as much as half a ton.

Ancient snakes may have also been nocturnal, according to experts. However, this trait has disappeared throughout the years due to the decreasing nighttime temperatures. It only reappeared around 50 million years later with the evolution of the family Colubroidea, which comprises 85% of all living snake species.

Surface-Terrestrial to Burrowing

Previous studies about snake evolution showed that snakes evolved from lizards. However, it remained a controversial topic for decades because there were not enough well-preserved fossils. Researchers previously established three hypotheses for the habitat of early snakes, including burrowing worm-like, terrestrial, or aquatic snakes. A 2018 study added another dimension to the investigation of snake origins. 

Researchers from the University of Helsinki found it difficult to collect reptile specimens covering all major groups of lizards and snakes. Still, they managed to compare the skull shape and size of over 300 species of lizards and snakes using an integrative approach. They collaborated with national history museums, digital morphology libraries, as well as paleontologists, biologists, and herpetologists. The team believed that the early snake habitats could be predicted from the skull structure.

"The diversity in cranial structure is remarkable and appears to be tightly linked to ecological habitat modes and diet preferences in lizards and snakes," Associate Professor Nicolas Di-Poï from the Institute of Biotechnology, University of Helsinki, said. 

Science Daily, an American website that aggregates press releases about science, reported that one of the findings of the study showed that snake evolution and diversification was an interplay between natural selection and developmental processes, and not a straightforward process. Snakes first acquired an underground lifestyle before adapting to various habitats such as water, forests, deserts, and prairies.

Previous studies about snake evolution showed that snakes evolved from lizards. However, it remained a controversial topic for decades because there were not enough well-preserved fossils / Photo by: Paulo Ragner via Shutterstock

 

Preserved Skull Showed Snakes Had Back Legs

In 2013, Fernando Garberoglio, from the Fundación Azara at Universidad Maimónides in Buenos Aires, Argentina, found a snake skull during his first field trip to the La Buitrera Paleontological Area. He was with two paleontologists: Guillermo Rougier, from the University of Louisville, and Sebastián Apesteguía, from the Universidad Maimónides. Little did he know that the snake fossil, which was a result of a painstaking discovery, would contribute a lot to the research of snake evolution. 

The snake fossil was identified as a Najash rionegrina, a type of early snake with hindlimbs. According to CNN, an American news-based pay television channel, the researchers reported that the Najash possessed primitive features more similar to lizards. It had more snakelike features like the lack of a bony arch connecting from the skull to the cheekbone. Najash also had some of the mobile skull joints that are typical of most modern snakes and large mouths with sharp teeth.

The researchers found that the Najash snakes lived with back legs in a successful and stable way for over 70 million years using light microscopy and tomography scanning. These allowed the team to see the primitive snake in 3D and better understand the early stages of evolution that led to modern snakes. This suggests that the hindlimbs of early snakes were not just a transitional phase but also were extremely useful to them. 

The snake fossil was identified as a Najash rionegrina, a type of early snake with hindlimbs / Photo by: Ketkata Leejungphemphoon via Shutterstock

 

Michael Caldwell, the study co-author and professor at the University of Alberta, said, "This research revolutionizes our understanding of the jugal bone in snake and non-snake lizards. After 160 years of getting it wrong, this paper corrects this very important feature based not on guesswork, but on empirical evidence."

The recent study published in the journal Science Advances supports the idea that snakes were big-bodied and big-mouthed. According to Live Science, a science news website that features groundbreaking developments in science, space, technology, health, the environment, our culture and history, the evolution tells us that snakes have been evolving towards the skull mobility necessary to ingest fairly large prey. 

In a statement, Garberoglio said, "The study also reveals that early snakes retained their hindlimbs for an extended period of time before the origin of modern snakes which are for the most part, completely limbless."

The recent discovery plays a critical role in understanding the evolution of the skulls of modern and ancient snakes. It has provided us with a deeper understanding of the snake body plan, which has baffled scientists for so long.