A new study suggests that the common ancestor of modern living snakes had vestigial limbs: ankles and toes. The findings have been published in BMC Evolutionary Biology.
What did the common ancestor of modern snakes look like? Snake evolution has been a challenging research area because of the fragility of the skeletons of the creatures that leave behind only few fossils. As a consequence, understanding how snakes have changed throughout time is tricky.
A new study led by Yale University paleontologists has perhaps solved part of the mystery. The researchers compared 73 snake and lizard species to determine the possible appearance of their common ancestor. It is believed that the world’s first snake ancestors were four-legged animals which gradually and ultimately evolved into snakes. What about the intermediate phases? How was the transition from four legs to no leg at all? The lack of fossils for each stage of snake evolution has greatly obstructed scientists from having a clear idea of the answer to these questions.
The new study, though, explains how an intermediate ancestor – the latest ancestor of living snakes – had remnants of limbs. The conclusion deduced by the scientists is most probably the most surprising piece of information to have ever been generated about snakes’ ancestors: it turns out that the little guys might have had tiny hind limbs, with ankles and toes. This finding was made possible by using both living and extinct species to generate a possible “picture” of how lizards and snakes diverged from each other.
“We generated the first comprehensive reconstruction of what the ancestral snake was like,” said Allison Hsiang, the lead author of the study.
Co-author Daniel Field explained, “Our analyses suggest that the most recent common ancestor of all living snakes would have already lost its forelimbs, but would still have had tiny hind limbs, with complete ankles and toes. It would have first evolved on land, instead of in the sea. Both of those insights resolve longstanding debates on the origin of snakes.”
These snakes allegedly appeared on land first. This is in contradiction to another theory: scientists in the past have suggested that they would have emerged from the ocean. If the researchers of the new study are right, these land-based snakes would have lived around 128.5 million years ago, at a time where mammalian and avian evolution were particularly bursting with activity.
The first snakes had small rear limbs. They could supposedly take considerably large prey. They lived in warm areas with water and vegetation readily available. Furthermore, these snakes might have been nocturnal, unlike most of today’s snakes.
The absence of complete legs might have aided the adaptation to marine environments and swamps.
These snakes might have lived for over 20 million years, after undergoing changes around 95-105 million years ago.