Allonautilus scrobiculatus, a nautilus found the waters of the South Pacific, is so rare that researchers only know of three people in history that have ever seen it in person. Now, three decades after the last encounter, this incredible living fossil has decided to pay one lucky researcher a second visit.

According to biologist Peter Ward, A. scrobiculatus was first discovered off of Ndrova Island in Papua New Guinea back in 1984.

"My colleague Bruce Saunders from Bryn Mawr College found Allonautilus first, and I saw them a few weeks later," Ward explained in a statement.

He added that at the time, the discovering pair took back a few specimens of the nautili for study. After closely examining the unusual creatures, they realized that A. scrobiculatus was unique even among nautili; and that's impressive, as it comes from a group of shelled sea-creatures that have barely changed for an estimated 500 million years.

"Some features of the nautilus - like the shell giving it the 'living fossil' label - may not have changed for a long time, but other parts have," said Ward.

In particular, the gills, jaws, and male reproductive structures of A. scrobiculatus were revealed to be very different from any other nautilus species. The species also boast another unique trait that is still quite the mystery to the researcher.

"It has this thick, hairy, slimy covering on its shell," Ward explained. "When we first saw that, we were astounded." (Scroll to read on...)

Driven by the insatiable curiosity characteristic of most scientists, the biologist and his colleagues had hoped to observe the animals for longer, perhaps to determine what purpose, if any, the unique shell coating served. Unfortunately A. scrobiculatus vanished from Papua New Guinea as suddenly as it appeared.

Not to be deterred, Ward returned to those memorable South Pacific waters in 2011, setting out underwater cameras and meaty bait in the hopes the nautili would show. It was four years of watching and waiting before the elusive creatures returned.

"This year, there were about 30 guys involved and each day we would all watch the movies from the night before at 8X speed," Ward said. "There were a lot of 'ohs' and 'ahs' [when the nautili showed up]."

According to Ward and his team, two Allonautilus appeared in all, around a depth of 600 feet below the water's surface. The two apparently proceeded to grapple over bait until a sunfish appeared - a traditionally lazy scavenger that we now know can become a vicious jellyfish murderer.

According to Ward, this third contender joined the fray and "for the next two hours, the sunfish just kept whacking [the nautili] with its tail." (Scroll to read on...)

It's not exactly the most elegant of scenes to mark the return of a very unique species, but Ward could not have been happier seeing these living fossils bickering over chicken scraps. He explained that because of the nautili's relatively 'outdated' design, they can only live at very specific depths - a restriction that makes adapting to changing seas particularly difficult.

"Once they're gone from an area, they're gone for good," Ward warned. "They swim just above the bottom of wherever they are - Just like submarines, they have 'fail depths' where they'll die if they go too deep, and surface waters are so warm that they usually can't go up there."

Still, being easily isolated and limited to pocket habitats, even in the ocean, has led to some stunning genetic diversity among these ancient creatures.  Allonautilus and it's unique adaptations is arguably the most interesting of all. Now Ward and his partners hope to launch more searches in regions similar to the waters around of Ndrova Island.

"It's only near this tiny island," he said. "This could be the rarest animal in the world. We need to know if Allonautilus is anywhere else, and we won't know until we go out there and look."

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