SCIENTISTS SAY FOSSILS SHOW PREHISTORIC SNAKE HAD LEGS.

Byline: John Noble Wilford The New York Times

Paleontologists say they have found the first compelling fossil evidence that long ago, snakes grew legs.

In a reappraisal of fossils from a limestone quarry in Israel, paleontologists identified specimens, previously thought to be a lizard species, as the most primitive known snake - so primitive that it still has short but well-developed hind limbs. This slender, 3-foot-long snake, Pachyrhachis problematicus, lived in a shallow sea 95 million years ago.

The discovery, reported last Thursday in the journal Nature, could be a significant step in determining the origin of snakes, which has been obscured by a frustratingly skimpy fossil record, and tracing their evolutionary history. Not only does it enable scientists to prove that early snakes did have legs, like other reptiles, but perhaps to establish more clearly their relationship to the wider order of lizards, one of the unsolved mysteries of evolution.

Questions about whether snakes ever had limbs and how they might have lost them have long intrigued scientists. Ancient people must have wondered, too, which would account for the story of the most famous snake of all, the source of temptation in the Garden of Eden.

When the serpent beguiled Eve into tasting of the tree of knowledge, according to the Book of Genesis, God condemned the serpent to go on its belly ``and dust shalt thou eat all the days of thy life.''

The two fossil specimens that Dr. Michael W. Caldwell of the University of Alberta in Edmonton, and Dr. Michael S.Y. Lee of the University of Sydney in Australia examined last year at Hebrew University in Jerusalem had two hind legs, each only a little more than an inch long. And these were not lizards, as they had been classified 20 years ago, when they were excavated at the Ein Jabrud quarries, 12 miles north of Jerusalem on the West Bank.

In their journal report, the two paleontologists said the small, narrow, lightly built skull of Pachyrhachis had many characteristics found only in snakes. The braincase is fully enclosed in bone. Other bones and the jaws are loosely connected, which gives snakes the wide-mouthed flexibility to swallow whole their prey of frogs and rodents. Even the number and nature of the vertebrae seemed to stamp the specimens as snakes.

Caldwell and Lee called this ``compelling evidence'' that Pachyrhachis was ``a primitive snake with a well-developed pelvis and hind limbs.''

In a telephone interview Wednesday, Dr. Nicholas C. Fraser, a paleontologist at the Virginia Museum of Natural History in Martinsville, agreed that this ``is unquestionably a primitive snake.''

He wrote an accompanying article in Nature commenting on the research.

Fraser said the scientists would probably meet with considerable resistance, and require much more evidence, before they could win over paleontologists to their second conclusion - the link between snakes and a particular group of marine lizards - based on the analysis of the fossils.

Since the snake fossils were found in marine sediments and so must have lived in the sea, Caldwell and Lee looked for and found anatomical characteristics linking it to a group of extinct marine lizards known as mosasauroids.

Most of these lizards were smaller than Pachyrhachis, though the best known of this group was the Mosasaurus, a huge sea monsters with jaws three-feet long. This group evolved later. Modern members of the group include monitor lizards like the Komodo dragon.