Illustration of the Reunion swamphen (Porphyrio caerulescens syn Apterornis coerulescens), also known as the Reunion gallinule, a hypothetical extinct species of rail that was endemic to the Mascarene island of Reunion. While only known from 17th and 18th century accounts by visitors to the island, it was scientifically named in 1848, based on the 1674 account by Sieur Dubois. A considerable literature was subsequently devoted to its possible affinities, with current researchers agreeing it was derived from the swamphen genus Porphyrio. It has been considered mysterious and enigmatic due to the lack of any physical evidence of its existence. Illustration by John Gerrard Keulemans from 'Extinct Birds: an attempt to unite in one volume a short account of those birds which have become extinct in historical times: that is, within the last six or seven hundred years: to which are added a few which still exist, but are on the verge of extinction' by Baron, Lionel Walter Rothschild, published in 1907.