A new study led by researchers at Yale University took a comprehensive look at the origin of snakes and suggests that they originally evolved on land and not in the sea. The team looked at fossils, the anatomy of 73 modern lizard and snake species and the genetics of lizard and snake species.
They found that the animals most likely originated as a stealthy hunter in the warm forests in the Southern Hemisphere about 128 million years ago. The first snakes also had small hind legs which included ankles and toes.
“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. By analyzing the genes, fossils and anatomy of 73 different snake and lizard species, both living and extinct, we’ve managed to generate the first comprehensive reconstruction of what the ancestral snake was like,” said Allison Hsiang in a statement.
Hsiang is the lead author of the paper published in the the open access journal BMC Evolutionary Biology.
By arranged the various specimens they studied in a evolutionary family tree, the team was able to demonstrate how various characteristics evolved over time.
The results suggest that snakes emerged about 128.5 million years ago, during the Early Cretaceous period, along with many species of birds and mammals on the supercontinent of Laurasia. The ancient snakes likely hunted vertebrates and invertebrates which were fairly large when compared to the prey hunted by lizards.
Unlike most reptiles of the time, the snakes were likely nocturnal originally but returned to being active during the day (diurnal) about 50 million years ago with the emergence of Colubroidea. Colubroidea is a “superfamily” of snakes which includes 85 percent of all currently living species.
There are currently 3,400 known, living, species of snakes and probably more hiding in unexplored habitats waiting to be discovered. They inhabit just about every ecosystem including land habitats, fresh and salt water. The researchers attribute the spread of the animals to their skill as “dispersers”.
Snakes have a range 4.5 times larger than lizards and have been known to travel more than 40,000 square miles in a lifetime. They are also able to acclimate themselves to ecosystems which might stop terrestrial animals, including a repeatedly demonstrated ability to acclimate to water.
Despite their success, the origins of snakes is poorly understood. Because their bones are small, delicate and do not fossilize easily the fossil record of snakes contains large gaps and is almost certainly incomplete, even where some fossil record of a period is available.
