By WILLIAM J. BROAD

For 33 years, Peter A. Rona has pursued an ancient, elusive animal, repeatedly plunging down more than 3,000 meters to the muddy seabed of the North Atlantic to search out and, if possible, pry loose his quarry.

Like Ahab from “Moby Dick,” he has failed time and again. Despite access to the world’s best equipment for deep exploration, he has always come back empty-handed, the creature eluding his grip. The animal is no white whale. And Dr. Rona is no mentally deranged Captain Ahab, but rather a distinguished oceanographer at Rutgers University in New Jersey. And he has now succeeded in making an intellectual splash with a new research report, written with a team of a dozen colleagues.

They have gathered enough evidence to prove that his scientific prey - an organism a bit larger than a poker chip - represents one of the world’s oldest living fossils, perhaps the oldest. The ancestors of the creature, Paleodictyon nodosum, go back to the dawn of complex life. And the creature itself, known from fossils, was once thought to have gone extinct some 50 million years ago.

Has the long pursuit frustrated him? “No,” Dr. Rona replied. “It’s science. It’s detective work. It’s about racking up one clue after another.” Still, in an interview at Rutgers, he said he looked forward to eventually capturing one of the creatures alive. “I think it’s likely,” he said, “if we can do the dives.”

Dr. Rona, an authority on the deep sea, enjoys cramming himself into a tiny submersible and falling into the abyss.

It takes more than two hours to descend to the creature’s abode. The environmental stability of that world - including its crushing pressures and icy darkness - means that some of its most famous inhabitants have survived for eons as evolutionary throwbacks, their bodies undergoing little change. For instance, sea lilies, marine animals with feathery arms, date back more than 400 million years.

Dr. Rona has found that P. nodosum thrives in restricted areas of Atlantic seabed. Its only visible feature consists of tiny holes arranged in sixsided patterns. He has photographed thousands of the hexagons and found that large ones have 200 or 300 holes.

Dr. Rona’s inability to catch the creature itself means that even though scientists have given it the fossil’s name, they still vigorously debate what it is. The main question is whether the hexagonal patterns are burrows or body parts, vacant residences or animal remains.

Other deep sea sleuths who share Dr. Rona’s fascination with P. nodosum can be found at Yale University and the Woods Hole Oceanographic Institution on Cape Cod, Massachusetts, as well as in France, Canada and the United Kingdom.

“He’s got the drive of curiosity,” said Adolf Seilacher, a paleontologist at Yale and co-author of the new paper, who first contacted Dr. Rona three decades ago to discuss the creature. “Real scientists, naturalists, are extremely curious.”

Dr. Seilacher added that P. nodosum was a most unusual animal, especially because the many holes at the surface of its abode link up below in a labyrinth of subsurface tunnels.

“It’s not just any fossil but a demonstration of a very complex way of life,” he said in an interview. “It’s a building plan, a behavior that makes this animal erect this gallery system. It’s a lifestyle that is very, very old.”

Dr. Seilacher said the earliest forms of Paleodictyon dated to the explosion of complex life in the Cambrian period 500 million years ago. The animals began existence in shallow waters and gradually expanded into the dark habitats of the deep sea.

Dr. Rona stumbled on the living fossil in 1976. He and his colleagues were towing a giant camera sled, its strobe lights firing every few seconds, lighting up the seabed and recording the images on big reels of 35-millimeter film. Weeks later, back in his Florida office, Dr. Rona examined the freshly developed film.

His head began to spin. What were all the holes? And what made the patterns?

In 1978, Dr. Rona and a colleague, George F. Merrill, published a paper that ruled out many possibilities and called the mystery animals “invertebrates of uncertain identity.”

Dr. Rona managed to visit the site repeatedly. On a submersible dive in 2003, he and Dr. Seilacher went down together. They became improbable movie stars. In 2003, IMAX released “Volcanoes of the Deep Sea,” a film for giant movie screens, featuring their hunt.

Dr. Rona talks excitedly of new dives to the world of Paleodictyon as well as the possibility of setting up a camera on the seabed that would try to catch a glimpse of the ancient survivor.

“It’s an exceptional window into the past,” he said of the creature. “Now we need to solve the mystery of what it is. We need to recover a specimen.”


A submersible in “Volcanoes of the Deep Sea,” a documentary film about an oceanographer’s hunt for an elusive undersea creature.


A fossil of P. nodosum, once thought to be extinct.