|Mesoplodon traversii (New Zeland Dept. of Conservation)|
The spade-toothed whale (Mesoplodon traversii) represented a big mystery for 140 years. This species has never been spotted in the wild and the only previously known specimens of this whale were a single mandible with teeth from an adult male (the holotype), collected from the Chatham Islands, New Zealand in 1872, and two skulls without mandibles, one from White Island, collected in the 1950s and one from Robinson Crusoe Island, Chile, collected in 1986.
This changed in December 2010 when two beaked whales, a mother and calf, stranded and died on Opape Beach on the North Island of New Zealand. However, it took 2 years to eventually find out the truth. These two stranded whales were in fact Mesoplodon traversii.
From their initial description the whales were identified as Gray’s beaked whales (Mesoplodon grayi), the most commonly stranding beaked whale around New Zealand. However, to confirm their identity, researchers from New Zealand amplified and sequenced two mitochondrial DNA regions. Sequences were compared to other species of the genus, among those Gray's beaked whale and DNA fragments retrieved from the reference specimens from Mesoplodon traversii. The latter matched the sequences of the two stranded animals and given that these are the only two complete specimens of the species ever spotted we can truly assume that this is the world's rarest whale.