Ebon Purple-capped Fruit-Dove (Ptilinopus hernsheimi ssp. marshallianus)
This somewhat enigmatic form is known only from a single specimen, originally conserved in spirit, which was collected in the year 1859, obviously on the Ebon Atoll, Marshall Islands.
The bird was originally described as a distinct species, but was later assigned as a subspecies to the Purple-capped Fruit-Dove (Ptilinopus porphyraceus Temminck), whose subspecies again were split off as distinct species in 2014, The Samoan Fruit-Dove (Ptilinopus fasciatus Peale), The Kosrae Fruit-Dove (Ptilinopus hernsheimi) and the Pohnpei Fruit-Dove (Ptilinopus ponapensis Finsch).
The Ebon Purple-capped Fruit-Dove had a size of about 23 cm, it was quite similar to the Kosrae Fruit-Dove but is said to have had the vent and the undertail coverts orange rather than yellow.
The Ebon Purple-capped Fruit-Dove is currently treated as being synonymous to the Kosrae Fruit-Dove, however, in my opinion, and seen in a geographical context, it appears indeed to be quite senseful to treat this form as a distinct taxon.
 S. Dillon Ripley; Hugh Birckhead: Birds collected during the Whitney South Sea Expedition. 51, On the fruit pigeons of the Ptilinopus purpuratus group. American Museum Novitates 1192. 1942
 Dirk H. R. Spennemann; Hemley Benjamin: Notes on the avifauna of Ebon Atoll, Republic of the Marshall Islands: observations gathered during a brief field trip, 17-22 June 1992, with some comments on the Marshallese nomenclature of birds. Majuro Atoll: Republic of the Marshall Islands, Ministry of Internal Affairs, Historic Preservation Office 1992
 David Gibbs, Eustace Barnes, John Cox: Pigeons and Doves, A Guide to the Pigeons and Doves of the World. Pica Press, Sussex 2001
 Dirk H. R. Spennemann: Extinctions and extirpations in Marshall Islands avifauna since European contact-a review of historic evidence. Micronesica 38(2): 253–266. 2006
 J. del Hoyo; N. J. Collar; D. A. Christie; A. Elliott; L. D. C. Fishpool: HBW and BirdLife International Illustrated Checklist of the Birds of the World. Barcelona, Spain and Cambridge UK: Lynx Edicions and BirdLife International 2014