Appearing like the punchline to an evolutionary riddle, a new fossil snake with legs has emerged from 95 million year-old deposits near Jerusalem. Its sedimentary surroundings suggest a seafaring lifestyle for this ancient reptile, but its advanced anatomy could overturn a current theory about the marine origin of snakes.This intriguing new species, dubbed Haasiophis terrasanctus , is the second limbed snake to come from the site of Ein Yabrud, an ancient marine environment broadly similar to the still, coastal waters of today's Bahamian reef.

The first such species, Pachyrhachis problematicus, plays a pivotal role in a scenario that places the ancestor of snakes in the sea.

But a riddle remains: why do these two snake species have hind limbs? If legs were the norm for snake ancestors, it would make sense to see the species' advanced anatomy as only superficially similar to more modern snakes. On the other hand, the stubby limbs on the fossil snakes might represent an evolutionary reversal, where snakes with advanced skull design regain hind limbs that were lost.

Rieppel said that it is difficult to tell how the legs themselves might have been used, since they are too small in relation to the animal's whole body to have any locomotor function. Modern pythons have a rudimentary hind limb, usually little more than a "claw" of cartilage tipped with bone that they use during mating and occasional fighting, and it is possible that Haasiophis' leg served a similar purpose.