"This is the first time a spade-toothed beaked whale has been seen as a complete specimen, and we were lucky enough to find two of them," said lead scientist Dr Rochelle Constantine.
"It's incredible to think that, until recently, such a large animal was concealed in the South Pacific Ocean and shows how little we know about ocean biodiversity," Constantine said.
Scientists used DNA evidence to prove that a mother and her male calf which stranded in New Zealand in late 2010 were the first animals of their kind ever seen.
Since the two animals are the only intact members of their species sighted, the spade-toothed beaked whale is the world's rarest whale.
The animals were initially misidentified as Gray's beaked whales, the most common beaked whale to strand in New Zealand.
However subsequent genetic analysis at The University of Auckland revealed that they were spade-toothed beaked whales.
"This is a real New Zealand story