Small Mangarevan Petrel (Pterodroma sp.)
There might once have been a population of small petrels closely related to Cook’s Petrel (Pterodroma cookii (G. R. Gray)) and Stejneger’s Petrel (Pterodroma longirostris (Stejneger)) breeding on the island of Mangareva, Gambier Islands in eastern Polynesia.
This assumed species is known only from the remains of a single bird, merely from a single wing.:
“I went to top of Mangareva island and found a body of Ducie shearwater eaten by cat (?) on hillside, near top.” 
These remains were then brought to the American Museum of Natural History in New York, USA, where they were investigated in the 1990s and found to very likely constitute some distinct form.:
“The only remains of this bird is a wing in a museum collection (AMNH, label no. 191743). It belongs to a small petrell: the wing pattern, as well as size, suggest that it is a Cookilaria, possibly close to P. leucoptera; it may represent a specimen of an extinct or an unknwon population. No evidence of the presence of such a pop- ulation (e.g. vocalisation) was obtained in 1995–96 during at least 10 nights on Mangareva.” 
The first account mentiones that the bird was most likely eaten by a cat, this little mention tells us more or less all about the fate of this species, if it indeed was a distinct species.
There are several seabird species known to have once bred on Mangareva, most are now gone, some still breed on the little islets around the main island, but most are now gone fore good.
 Whitney South Sea Expedition of the American Museum of Natural History. Extracts from the journal of Rollo H. Beck. Vol. 1, Sept. 1920 – June 1923
 Jean-Claude Thibault; Vincent Bretagnolle: Breeding Seabirds of Gambier Islands, Eastern Polynesia: numbers and changes during the 20th century. EMU 99: 100-107. 1999