Maybe if snakes had adorable little ankles and toes, we wouldn't be so scared of them. A comparison of 73 snake and lizard species found that early in their evolution, they probably did. That didn't stop them being terrifying predators on small vertebrates, which at the time included our ancestors, who maybe didn't think too much about the cute little hind-limbs while being eaten.
It is no surprise that snakes, having evolved from four legged animals, went through a stage of having vestigial limbs. However, a paper in BMC Evolutionary Biology claims to have revealed more about them at that time than ever before. According to the researchers, these snakes first appeared on land, rather than in the oceans as some have previously argued, around 128.5 million years ago, coinciding with a burst of mammalian and avian evolution.
The last decade has been a good one for the discovery of early snake fossils, with the discover of specimens from several species. Nevertheless, we don't have fossils mapping each stage of snake evolution.
However, by using a mix of living and extinct species Yale's Daniel Field and Dr Allison Hsiang have created a picture they claim represents the point where the ophidian line diverged between lizards and snakes. The genetic and phenotypic family trees created do not always line up, the authors acknowledge, leaving considerable uncertainty, but there is enough consistency in what we can establish to create some confidence in what the last common ancestor looked like.
The authors conclude the first snakes had very small rear limbs and went after prey larger than the lizards of the day could tackle, despite lacking the capacity developed by modern pythons to constrict prey.
These ancestral snakes lived in “warm, well-wartered, well vegetated environments – not unlike today's forests,” Hsiang and Field claim, and were probably nocturnal, unlike most of their modern descendants.
While the absence of legs might be thought to hinder mobility, the authors conclude that snakes are much better dispersers than lizards, covering areas 4.5 times larger, as well as adapting to marine environments and swamps in a way their legged relatives never managed.
After slithering around relatively unchanged for more than 20 million years, a significant divergence took place 95-105 million years ago when many now-extinct species appeared in Gondwana. The resulting groups, such as the Matsoiidae, flourished for a long time, and representatives such as the giant Wonambi, survived into the last Ice Age.
Presumably a lot of snakes died in the immediate aftermath of the asteroid that destroyed the dinosaurs, but the survivors flourished, with many new species of henophidian snakes, a super family that now includes boas and pythons, appearing shortly thereafter.