Forbes' snipe

The Forbes' snipe, Coenocorypha chathamica, was a species of New Zealand snipe endemic to the Chatham Islands. It was the larger of two species found there, the smaller being the surviving Chatham Island snipe. It was never seen alive by scientists and is known only from fossil material collected on the islands. Why it became extinct while its smaller relative survived is a mystery, as is the exact timing of its extinction, although it may have survived, unnoticed, until the 19th century.