Hypothetical species

Several species have been assumed to exist, but due to a lack of physical evidence they can only be regarded as potential species. Hypothetical species are usually believed to be extinct. They have caused confusion, as they may have been a separate species, a subspecies, an introduced species or a misidentification.

Birds

 * Bird of Washington
 * Dominican green-and-yellow macaw
 * Eos unicolor
 * Gallus giganteus
 * Geoffroyus aureus
 * Guadeloupe amazon
 * Guadeloupe parakeet
 * Hypothetical relatives of the Rodrigues parrot
 * Jamaican red macaw
 * Lesser Antillean macaw
 * Lorius tibialis
 * Madeira finch
 * Martinique amazon
 * Martinique macaw
 * Painted vulture
 * Red-headed macaw
 * Réunion swamphen
 * Sushkin's goose

Non-avian dinosaurs

 * Proavis

Mammals

 * Andean wolf
 * Bili Ape
 * Chilihueque
 * Chinese elephant
 * Giraffa sahara
 * Kallana
 * Kting voar
 * Long-necked seal
 * Marozi
 * Tailed slow loris
 * Sonnerat's shrew
 * Steller's sea ape
 * Sumxu
 * Unidentified extinct canid populations

Fish

 * Abyssal rainbow gar
 * Bathyceratias
 * Bathyembryx
 * Bathysidus
 * Bathysphaera

Insects

 * Battus polydamas antiquus

Microanimals

 * Mesotardigrada
 * Salinella

Plants

 * Laysan fan palm
 * Silphium