Recently Discovered 4-Legged Snake Fossil May Actually be a New Prehistoric Animal Species

According to recent research, a dinosaur-era fossil hailed as the first four-legged snake known to science may be a completely different species.

Fossil Discovery

The tiny fossil, which measures 7.7 inches (19.5 centimeters) in length and is about the size of a pencil, is most likely a dolichosaur, a now-extinct marine lizard with an elongated body that lived during the Cretaceous Period (145 million to 66 million years ago), according to the study's researchers.

According to study lead researcher Michael Caldwell, a professor in the Department of Biological Sciences and the Chair of the Faculty of Science at the University of Alberta in Edmonton, Canada, the creature, known as Tetrapodophis amplectus (the genus in Greek means "four-legged snake," while the species is Latin for "embracing"), "the specimen does not have key anatomical features characteristic of snakes."

Criticizing Fossil Treatments

Furthermore, the new study criticizes the treatment of the Tetrapodophis fossil, which may have been illegally exported from Brazil and whose original study included no Brazilian researchers, despite a Brazilian law requiring that researchers from their country be included in the study of Brazilian specimens.

Scientists have long assumed that snakes had four legs; two studies published in the journal Cell in 2016 revealed that snakes lost their limbs approximately 150 million years ago due to genetic abnormalities. Other studies have even discovered fossil evidence of a two-legged snake. Tetrapodophis is the only four-legged snake fossil known, having been discovered in 2015 and published in the journal Science.

Tetrapodophis

According to Live Science, Tetrapodophis utilized its four limbs, each with five digits, not for walking when it was alive 120 million years ago, but for holding mates during mating and clutching hostile prey when hunting. The researchers believe this species developed from terrestrial-burrowing creatures during the transition from prehistoric lizards to modern-day snakes.

Caldwell and Robert Reisz, a vertebrate paleontologist at the University of Toronto and a co-author of the current research, disagreed with that interpretation of the fossil. So they traveled to Germany, where the privately owned Tetrapodophis was on display at the Solnhofen Museum (previously known as the Bürgermeister-Müller-Museum), to conduct their microscopic examination, which they first reported at the Society of Vertebrate Paleontology annual conference in 2016.

The latest study, published online Nov. 17 in the Journal of Systematic Palaeontology, discovered evidence that Tetrapodophis was more lizard-like than serpentine, notably in the head. Caldwell described most of the skull's bones as "crushed like an eggshell," with shards of a broken skull on one slab and the natural mold of the skull on the other. "The counterpart of the skull is the one thing that the original authors utterly disregarded," he remarked. "We notice some additional lizard-like traits in the natural mold, not snake-like ones."

Debunking Misconceptions

Tetrapodophis did not have a snake-like body, according to the researchers. For example, the slender Tetrapodophis fossil lacks zygosphenes and zygantra. These vertebral stabilizing structures let a snake slither back and forth, and it has long, straight ribs, indicating that it was a swimmer rather than a burrower, as the original research claimed. Caldwell explained, "Burrowing creatures tend to be long and tubular."

Dolichosaurs are closely linked to snakes, according to research co-author Tiago Simes, a postdoctoral scholar at Harvard University's Museum of Comparative Zoology. It's likely no wonder, however, that the original writers mistook Tetrapodophis for a snake, according to the researchers.

However, this isn't a cut-and-dry situation. "Tetrapodophis is a fantastic fossil, displaying a unique combination of features not seen in any other squamate [lizards, snakes, and amphisbaenians]," said Bruno Gonçalves Augusta, an associate researcher at the University of So Paulo's Museum of Zoology and Southern Methodist University in Texas who was not involved in either study. However, he cautioned that some of the novel findings derived from the ancient analog, or mold, should be treated with care.

"For example, I disagree with their assessment of quadrate [cranial bone] morphology," Gonçalves Augusta told Live Science in an email. "The real bone is not preserved on the fossil, only a natural imprint (a mold) is there... which I don't think is a trustworthy source of information."

Other scientists cannot examine the fossil independently since the privately owned specimen is not available to them, according to Gonçalves Augusta. "Making personal observations and fully studying the creature is no longer possible," he stated.