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First Snakes Likely Had Legs and Toes?

May 20, 2015 11:41 AM EDT

Today's snakes are known for slithering on the ground, but new surprising research says that the first snakes on Earth were likely stealthy predators that boasted legs, ankles, and even toes.

A team of scientists at Yale University analyzed fossils, genes, and anatomy from 73 snake and lizard species, and suggests that snakes first evolved on land, not in the sea, like some experts believe.

According to the study, these ancient reptiles probably originated in the warm, forested ecosystems of the Southern Hemisphere around 128 million years ago.

While scientists know of over 3,400 snake species, living in a wide range of habitats, from land and water to trees, where and when they evolved largely remains a mystery, as well as how their original ancestor looked and behaved.

"While snake origins have been debated for a long time, this is the first time these hypotheses have been tested thoroughly using cutting-edge methods," lead author Allison Hsiang said in a press release. "We've managed to generate the first comprehensive reconstruction of what the ancestral snake was like."

By identifying similarities and differences between species, the team constructed a large family tree and illustrated the major characteristics that have played out throughout snake evolutionary history.

Their results suggest that snakes were first found on land, rather than in water, during the middle Early Cretaceous period (around 128.5 million years ago), and most likely came from the ancient supercontinent of Laurasia.

More interestingly, the ancestral snake likely possessed a pair of tiny hindlimbs, and had an appetite for soft-bodied vertebrate and invertebrate prey that were relatively large in size compared to prey targeted by lizards at the time.

Modern snakes like the Boa constrictor, on the other hand, are known for having a talent of swallowing prey much larger than itself. But the first snakes on Earth had not yet developed this unique ability, and so had to resort to eating very small animals.

Furthermore, unlike many ancestral reptiles, the first snakes were supposedly nocturnal. Diurnal habits later returned around 50-45 million years ago with the appearance of Colubroidea - the family of snakes that now make up over 85 percent of living snake species.

The Yale team speculates that today's snakes are now diurnal, or daytime predators because colder night temperatures hindered nocturnal activity.

Over the course of their evolutionary history, snakes have had much success in occupying a range of habitats, partly due to their skills as "dispersers." In fact, snakes are estimated to be able to travel ranges up to 110,000 square kilometers (~42,500 sq. miles) - that's around 4.5 times larger than lizards.

Now, thanks to this study, we know it was possible that the first snakes on Earth walked their way to new, unique habitats using their legs and feet.

The findings were published in the journal BMC Evolutionary Biology.

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