Story highlights The spade-toothed beaked whale is rarest of whales

Scientists only had partial skeletal remains of the species before

An adult female and juvenile male washed up on a New Zealand beach in 2010

Only months later did researches know what they had

It is the world's rarest whale and one of its rarest mammals.

Almost a thing of legend, scientists have never seen a spade-toothed beaked whale alive and, until recently, only had limited skeletal evidence they existed.

So rare is the species that when a pair of dead whales washed up on a New Zealand beach in late 2010, scientists didn't even know what they had.

But now they do ... and they're a bit giddy.

Another co-author, Rochelle Constantine with the School of Biological Sciences at the University of Auckland, made the discovery in 2011 while testing tissue samples from the whales with colleague Kirsten Thompson.

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"When she showed me the result we were both a bit stunned," Constantine said. "We re-ran the sample again to make sure, even though the DNA clearly showed it was a spade-toothed beaked whale."

The results were stunning because only three partial specimens of the species were known to exist -- two collected in New Zealand in 1872 and in the 1950s and a third found on Robinson Crusoe Island off the coast of Chile in 1986.

The spade-toothed beaked whale looks similar to a large black, white and gray dolphin with its long pointed snout. Scientists believe they grow to be about 17 feet long. Adult males have large exposed teeth as the name suggests.

Mistaken for a Gray's beaked whale after their discovery, the adult female and juvenile male were buried near where they were found on Opape Beach. Scientists were anxious to recover the remains and did in early 2012.

"We now have collected the only complete specimen in the world of this rarest of whales," van Helden said. "Sadly the head of the adult female had washed away through beach erosion."

Still, the recovery of the remains is a bonanza for scientists who study cetaceans.

"Yes, the discovery is indeed most exciting," said geology professor Ewan Fordyce , who studies the evolution of whales and dolphins at University of Otago but who was not involved in the research. "Now we have an idea of the appearance and size of the species."

Its lifestyle and habits are another story -- not surprising for a species researchers have never seen alive.

Scientists can only guess based on what they know about other beaked whales, which are often boat-shy, spend little time at the surface and dive to depths of 6,600 feet (about 2,000 meters), according to van Helden. They probably dine on squid.

Yet, scientists are excited by the challenge.

"This is the species of whale that we know the least about in the world," Constantine said. "It has never been seen before, as far as we know, and for the first time we have an idea of what it looks like."