Ancient Snake Fossil Reveals Clues on How Snakes Lost Legs

Ancient snake fossil reveals clues on how snakes lost legs, supporting emerging hypotheses that they transited from a land environment to the marine environment.

The ancient snake fossil has been unearthed in Argentina and is dated to 90 million years ago. At the time, the researchers suggest, the ancestors of modern-day snakes would have sported legs much like lizards do nowadays. However, in the evolutionary process, the legs would have become a nuisance and a disadvantage. Forced to follow their prey in the narrowest of spots, the legs became obsolete. In addition, making a transition between land habitat and the marine habitat pushed for the loss of legs in the evolutionary process.

The ancient snake fossil, titled Dinilysia Patagonica, complete with the skull was analyzed by researchers at the University of Edinburgh and the American Museum of Natural History, New York. In order to understand the evolutionary process at play, the research team led by Hongyu Yi with the University of Edinburgh and Mark Norell with the American Museum of Natural History, created 3D models of the inner ear based on the skull of the ancient snake fossil.

Using CT scans, the 3D models revealed that the snake living 90 million years ago had a unique structure of the inner ear, complete with bony canals as well as cavities which play a crucial role in detecting both predators and their prey.

The same structure is now present with nestling lizards, as well as some snakes. However, it misses entirely in snakes living above ground, as well as marine snakes. The inner ear is notoriously important for balance. With snakes, it also helps them detect both predators and the prey in their surroundings.

With the help of the 3D models of the inner ear the ancient snake fossil reveals clues on how snakes lost legs. According to the researchers publishing their findings in the Science Advances journal, Dinilysia patagonica was the largest burrowing snake ever known. Another hypothesis stemming from this research is that crown snakes also descend from burrowing snakes the likes of Dinilysia patagonica. However, more research is needed to establish the link.

Hongyu Yi declared that while it has long been a mystery how snakes shed their legs, the new research suggests that it happened as they became better at burrowing and the evolutionary process developed around this advantage.

Photo Credits: Wikimedia