The researchers also concluded from a close re-examination of snake fossils that they originated in the sea, rather than underground.

According to the scientists, the snakes lived in the Jerusalem area 100 million years ago and were discovered in a quarry at Ein Yabrud, near Ramallah, about a quarter of a century ago by the late Hebrew University Professor George Haas.

A team from the Silberman Institute of Life Sciences, led by Professor Eitan Tchernov, found the fossils had two small but anatomically complete hind legs. Tchernov will present his findings at next month's international conference of the Society of Vertebrate Paleonotology in Chicago.

Haas discovered three well-preserved snake fossils in the quarry and determined that they were among the most primitive snakes ever encountered. They also showed the development from the lizard to the snake. However, new methods of evolutionary research allowed Tchernov and colleagues to re-study the fossils and reveal characteristics that had previously been ignored.

Scientists had believed that snakes developed from an unknown group of lizards that lived underground and that — in adapting to their environment — "lost" their legs and acquired the coiling-snake form we know today.

But Tchernov says the snakes developed from animals that lived in the prehistoric Tethys Ocean, which intermittently covered an area that included Israel. Since the fossils sank within a closed bay and were not in contact with oxygen, they were in excellent condition. Therefore, he said, one can theorize that their origin was as sea-dwelling lizards and not land animals.

The findings, which are regarded as quite revolutionary, have aroused much debate among scientists. They disagree on whether the Ein Yabrud snakes represent the direct ancestors of contemporary snakes or are representative of just one type, which came from those ancestors but did not survive into the modern world.

Tchernov says he can't prove all of today's snakes originated with these sea snakes, and says the question is still open. But the matter will become clearer in the next few months, when he completes his study of the third and last of the fossils using modern scanning methods. These will give a full description of the inside and outside of the fossil.

Tchernov hopes it will be possible to return to the site near Ramallah in the near future, together with U.S. scientists, to seek new paleontological finds.

The snakes of Ein Yabrud — the most complete and best preserved collection of snake fossils — are part of the National and University Fossil Collection at Hebrew University's science faculty. It is expected to serve as the base for a new museum of natural history initiated by Hebrew University Professor Jeff Camhi.