An animal so rare that only two people are thought to have ever seen it until now has been photographed and briefly captured in the South Pacific.
The creature is a species of nautilus, a group of animals related to squid that have a spiral shell like a snail. They're known as living fossils as they have existed for almost 500 million years — since shortly after the first trilobites evolved during the Cambrian period.
The rare nautilus is a species known as Allonautilus scrobiculatus, which has a distinctive, slimy, hairy coating on its shell. Its gills, jaws, shell shape and male reproductive organs are also very different from those of other nautilus species, according to Peter Ward, the University of Washington biologist who saw and captured it, along with other some other nautilus species.
He and his colleagues took small tissue, shell and mucous samples last July before releasing the animals back into the ocean where they had been caught, about 180 metres below the surface near Ndrova Island off Papua New Guinea, said a news release from the University of Washington.
Before that, the animal had last been glimpsed in 1986 by Bruce Saunders, a biologist at Bryn Mawr College who first discovered the species in 1984. He and Ward — who saw the species a few weeks after Saunders first discovered it — were the only humans known to have ever seen it until now.
"This could be the rarest animal in the world," Ward said in a statement.
Ward captured the creatures while surveying nautilus populations near Papua New Guinea. His team of 30 species suspended chicken meat between 150 and 400 metres below the surface, then filmed the creatures that came to the bait for 12 hours.
After seeing Allonautilus in one night's footage, they used baited traps to capture several different species of nautilus temporarily for study.
DNA analysis shows that nautilus populations from different nearby islands or coral reefs are typically quite genetically different from one another. Ward thinks this is because they can only live in a very narrow layer of water at a certain depth.
That means that individual species are very vulnerable to threats such as illegal fishing and poaching for their shells.
In September, the U.S. Fish and Wildlife Service will decide whether to recommend protecting nautiluses under the Convention on International Trade in Endangered Species of Wildlife Fauna and Flora, an international agreement that restricts the trade and import of threatened species.