Kawekaweau was a giant forest gecko in New Zealand. Only one person had seen a living specimen — and he'd killed it. Then a stuffed gecko turned up in a museum, in France. No one knows where it came from.
Scientists only know about kawekaweau, a large brown gecko that lived in the forests of New Zealand, second-hand. There were legends about it, but no modern scientist had ever seen one. They were long-extinct. The closest any encounter any biologist had ever had with one happened in 1873, when he heard a Maori chief describe killing a kawekaweau in 1870. The biologist wrote, "He described it to me as being about two feet long and as thick as a man's wrist; colour brown, striped longitudinally with dull red."
Then, in 1986, researchers going through the basement of the Natural History Museum of Marseille, in France, came across an unlabeled specimen. It was a gecko, roughly two feet long, with "dark reddish-brown longitudinal dorsal stripes." Scientists took a closer look, comparing it with both surviving descriptions of the famous gecko, and with the physiology of its closest living relatives, and determined that this dead stuffed relic was the only physical specimen of the giant gecko in the world.
The specimen got the scientific name Hoplodactylus delcourti, for Alain Delcourt, the assistant in charge of the herpetology collection at the Marseille museum. No one has been able to find out anything about the gecko, including when or how it came to Marseille. The stuffed gecko went to the National Museum in Wellington in 1990. It remains elusive. There are few pictures of it online. (The image above is of its smaller relative, Hoplodactylus duvaucelli.) If you want to look at the thing, here is the 1986 paper that describes it.