''Apteribis'' is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

flightless bird Flightless birds are birds that cannot Bird flight, fly, as they have, through evolution, lost the ability to. There are over 60 extant species, including the well-known ratites (ostriches, emus, cassowary, cassowaries, Rhea (bird), rheas, an ...

s in the

ibis The ibis () (collective plural ibises; classical plurals ibides and ibes) are a group of long-legged wading birds in the family Threskiornithidae that inhabit wetlands, forests and plains. "Ibis" derives from the Latin and Ancient Greek word f ...

subfamily that was

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

to the

Hawaiian Islands The Hawaiian Islands () are an archipelago of eight major volcanic islands, several atolls, and numerous smaller islets in the Pacific Ocean, North Pacific Ocean, extending some from the Hawaii (island), island of Hawaii in the south to nort ...

in the

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...

Distribution

The remains of the small ibises in the genus have only been found on the islands of

Maui Maui (; Hawaiian language, Hawaiian: ) is the second largest island in the Hawaiian archipelago, at 727.2 square miles (1,883 km2). It is the List of islands of the United States by area, 17th-largest in the United States. Maui is one of ...

Lanai Lānai is the sixth-largest of the Hawaiian Islands and the smallest publicly accessible inhabited island in the chain. It is colloquially known as the Pineapple Island because of its past as an island-wide pineapple plantation. The island's on ...

, and

Molokai Molokai or Molokai ( or ; Molokaʻi dialect: Morotaʻi ) is the fifth most populated of the eight major islands that make up the Hawaiian Islands archipelago in the middle of the Pacific Ocean. It is 38 by 10 miles (61 by 16 km) at its g ...

, which formed part of the prehistoric island of

Maui Nui Maui Nui is a modern Geology, geologists' name given to a prehistoric Hawaii, Hawaiian island and the corresponding modern Biogeography, biogeographic region. Maui Nui is composed of four modern islands: Maui, Molokai, Molokaʻi, Lanai, Lānaʻi, ...

until about 200,000 years ago when

rising sea levels The sea level has been rising from the end of the last ice age, which was around 20,000 years ago. Between 1901 and 2018, the average sea level rose by , with an increase of per year since the 1970s. This was faster than the sea level had e ...

fragmented it. Olson and James speculate that the genus was endemic to Maui Nui, that the ibises were birds of the

forest floor The forest floor, also called detritus or wikt:duff#Noun 2, duff, is the part of a forest ecosystem that mediates between the living, aboveground portion of the forest and the mineral soil, principally composed of dead and decaying plant matter ...

, that because of their flightlessness they were susceptible to becoming trapped in

lava tube A lava tube, more rarely called a pyroduct, is a 'roofed conduit through which molten lava travels away from its vent'. If lava in the tube drains out, it will leave an empty cave. Lava tubes are common in low-viscosity volcanic systems. La ...

s, and that they may have exerted heavy

predation Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...

pressure on Maui Nui's

land snail A land snail is any of the numerous species of snail that live on land, as opposed to the sea snails and freshwater snails. ''Land snail'' is the common name for terrestrial molluscs, terrestrial gastropod mollusks that have gastropod shell, shel ...

Taxonomy

Analysis of the feathers from the Lanai specimen show an affinity to New World ibises of the genus '' Eudocimus''. The analyses also concluded that ''Apteribis'' may have had a brown-and-beige coloration similar to that of a juvenile ''Eudocimus'' ibis. This indicates that ''Apteribis'' may have evolved both their flightlessness and their coloration through a form of

paedomorphosis Neoteny (), also called juvenilization,Montagu, A. (1989). Growing Young. Bergin & Garvey: CT. is the delaying or slowing of the Physiology, physiological, or Somatic (biology), somatic, development of an organism, typically an animal. Neoteny i ...

Species

Two species have been described: * †''A. glenos'' Olson & Wetmore, 1976, the Moloka'i flightless ibis * †''A. brevis'' Olson & James, 1991, the Maui flightless ibis The

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

of ''A. glenos'' is from the Moʻomomi dunes, and other specimens are from Ilio Point and Kalaupapa peninsula. Fossil material collected on Maui indicates that a third species apparently occurred there; it was generally larger in size and occurred at lower elevations than ''A. brevis'', and has been referred to as the “Maui lowland apteribis”. Another, extremely well-preserved specimen has also been recovered from Lanai, though it has not yet been described to the species level.

References

Notes

{{Taxonbar, from=Q1557120 Bird genera † Holocene extinctions Late Quaternary prehistoric birds Extinct birds of Hawaii Maui County, Hawaii † Fossil taxa described in 1976 Taxa named by Alexander Wetmore