A fossil of a four-legged snake initially thought to be an evolutionary missing link has turned out to be an entirely different animal altogether. Researchers had long expected to find a fossil of the theoretical evolutionary step from lizards to snakes so its discovery was originally heralded as an archaeological and paleontological breakthrough. However, given the results of this most recent study that search will have to continue.
BACKGROUND: WE HAVE FOUND THE MISSING LINK
In 2015, researchers studying a fossil from Brazil noted the animal’s unusual physiology, which seemed to share characteristics of both lizards and snakes.
“[The fossil] contains a snakelike species that is elongate and serpentine, with both hind and forelimbs,” the original research paper states. “This species appears to have been a burrower and shows clearly the early transitional stages from a lizard-like body plan to the smooth legless snakes we know today.”
That discovery faced almost immediate scrutiny. However, due to legal issues, the fossil itself had previously been unavailable for more study.
ANALYSIS: CORRECTION: WE HAVE NOT FOUND THE MISSING LINK
“It has long been understood that snakes are members of a lineage of four-legged vertebrates that, as a result of evolutionary specializations, lost their limbs,” said Michael Caldwell, a paleontologist from the University of Alberta and lead author of the latest study, via Phys.org. “Somewhere in the fossil record of ancient snakes is an ancestral form that still had four legs. It has thus long been predicted that a snake with four legs would be found as a fossil.”
Published in the Journal of Systematic Paleontology, and titled, “Tetrapodophis amplectus is not a snake: re-assessment of the osteology, phylogeny and functional morphology of an Early Cretaceous dolichosaurid lizard,” Caldwell and his team’s study undoes the original 2015 assessment and instead notes that the fossil in question is from an entirely different species of extinct lizard.
“There are many evolutionary questions that could be answered by finding a four-legged snake fossil, but only if it is the real deal,” said Caldwell. “The major conclusion of our team is that Tetrapodophis amplectus is not in fact a snake and was misclassified.”
“Rather,” Caldwell added, “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.”
OUTLOOK: THE SEARCH FOR A FOUR LEGGED SNAKE CONTINUES
Study co-author Tiago Simões, who is a former University of Alberta Ph.D. student, a Harvard post-doctoral fellow and Brazilian paleontologist, also notes the legal issues that have stalled the study of the fossil since its discovery, as well as the recommendations made by the team regarding its ongoing legal status.
“There were no appropriate permits for the specimen’s original removal from Brazil and, since its original publication, it has been housed in a private collection with limited access to researchers,” said Simões, who also noted the frustration this situation caused within the research community. “In our redescription of Tetrapodophis, we lay out the important legal status of the specimen and emphasize the necessity of its repatriation to Brazil, in accordance not only with Brazilian legislation but also international treaties and the increasing international effort to reduce the impact of colonialist practices in science.”
For now, the search for a fossilized snake with four limbs will have to continue. However, according to my wife who has worked at some of the country’s largest law firms throughout her legal career, finding a snake walking on two limbs is incredibly easy.
Follow and connect with author Christopher Plain on Twitter: @plain_fiction