Nautiluses, called living fossils because they have survived 500 million years, are now threatened by overharvesting and seafloor mining.

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In 1984, University of Washington biologist Peter Ward and a colleague discovered a new type of nautilus in the deep ocean off Papua New Guinea.

Then the creature seemed to vanish.

For nearly 30 years, no sightings were reported. Ward and other experts feared it was extinct.

But last month, Allonautilus scrobiculatus swam into view once again as Ward and a team of scientists were surveying the same region of the South Pacific.

Nautiluses, called living fossils because they have survived 500 million years, are now threatened by overharvesting and seafloor mining. A UW biologist spotted the rare Allonautilus for the first time in three decades. (Courtesy of Gregory Barord)

“This could be the rarest animal in the world,” said Ward, one of the few researchers to study nautiluses. Related to squid and cuttlefish, the odd-looking sea animals are often called living fossils because they appear to have changed little in the past 500 million years.

The best-known species is the chambered nautilus, revered for the beauty of its spiral shell.

But when Ward and Bruce Saunders, of Bryn Mawr College, first spotted Allonautilus, what struck them most was the hairy, slimy covering on its shell.

“It reminds me of half a swimming ear muff,” Ward said. “It’s just a shaggy dog.”

For this summer’s surveys, Ward and his crew lowered cages of fish and chicken meat into water 500 to 1,300 feet deep to lure nautiluses — which are scavengers — so they could be filmed. Every evening, the team reviewed the footage with local villagers.

To their astonishment, the first film segment to capture Allonautilus in action played out like a nature documentary, Ward said.

A slimy nautilus swam up to the bait and was trying to feed on it when a chambered nautilus muscled in and the two battled for supremacy. Then both of the smaller creatures were shouldered aside by an 8-foot-long sunfish.

“About 50 villagers were squeezed around this one laptop, and there were a lot of ‘oohs’ and ‘ahhs,’ ” Ward said.

The researchers glued radio tags to four Allonautiluses and tracked their movements, following close behind in a small motor boat because the transmitter range was so short. They also captured several, measuring each and taking small tissue samples before returning them to the water.

Because their shells are valued for jewelry and ornaments, all species of nautilus are in peril, Ward said. The U.S. Fish and Wildlife Service estimates that more than half a million nautilus shells or pieces of shell were imported into the U.S. between 2005 and 2008.

And the government of Papua New Guinea recently approved seafloor mining around the two small islands that are the only places in the world where Allonautilus have been found.