Aepyornis Maximus
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''Aepyornis'' is an extinct genus of
elephant bird Elephant birds are extinct flightless birds belonging to the Order (biology), order Aepyornithiformes that were native to the island of Madagascar. They are thought to have gone extinct around 1000 CE, likely as a result of human activity. Eleph ...
formerly
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
Madagascar Madagascar, officially the Republic of Madagascar, is an island country that includes the island of Madagascar and numerous smaller peripheral islands. Lying off the southeastern coast of Africa, it is the world's List of islands by area, f ...
. The genus had two species, the smaller ''A. hildebrandti'' and the larger ''A. maximus'', which is possibly the largest bird ever to have lived. Its closest living relative is the New Zealand kiwi. They became extinct sometime around 1000 AD, probably as a result of human activity.


Taxonomy

Brodkorb (1963) listed four species of ''Aepyornis'' as valid: ''A. hildebrandti'', ''A. gracilis'', ''A. medius'' and ''A. maximus''. However, Hume and Walters (2012) listed only one species, ''A. maximus''. Most recently, Hansford and Turvey (2018) recognized only ''A. hildebrandti'' and ''A. maximus''. * ?''Aepyornis grandidieri'' Rowley 1867 nomen dubium * ''Aepyornis hildebrandti'' Burckhardt, 1893 ** ''Aepyornis gracilis'' Monnier, 1913 ** ''Aepyornis lentus'' Milne-Edwards &
Grandidier Grandidier is a surname. Notable people with the surname include: *Alfred Grandidier (1836–1921), French naturalist and explorer *Ernest Grandidier (1833–1912), French industrialist, naturalist, and art collector, brother of Alfred *Guillaume G ...
, 1894
** ?''Aepyornis minimus'' ** ?''Aepyornis mulleri'' Milne-Edwards &
Grandidier Grandidier is a surname. Notable people with the surname include: *Alfred Grandidier (1836–1921), French naturalist and explorer *Ernest Grandidier (1833–1912), French industrialist, naturalist, and art collector, brother of Alfred *Guillaume G ...
, 1894
* ''Aepyornis maximus'' Hilaire, 1851 ** ''Aepyornis cursor'' Milne-Edwards &
Grandidier Grandidier is a surname. Notable people with the surname include: *Alfred Grandidier (1836–1921), French naturalist and explorer *Ernest Grandidier (1833–1912), French industrialist, naturalist, and art collector, brother of Alfred *Guillaume G ...
, 1894
** ?''Aepyornis intermedius'' ** ''Aepyornis medius'' Milne-Edwards &
Grandidier Grandidier is a surname. Notable people with the surname include: *Alfred Grandidier (1836–1921), French naturalist and explorer *Ernest Grandidier (1833–1912), French industrialist, naturalist, and art collector, brother of Alfred *Guillaume G ...
, 1866
** ''Vorombe titan'' (Andrews 1894) Hansford & Turvey 2018, The nominate species ''Aepyornis titan'' Andrews, 1894, was placed in the separate genus ''Vorombe'' by Hansford and Turvey (2018), with ''A. ingens'' a synonym of ''titan''. ''Aepyornis grandidieri'' Rowley, 1867 is an ootaxon known only from an eggshell fragment and hence a ''nomen dubium''. Hansford and Truvey (2018) also found ''Aepyornis modestus'' a senior synonym of all '' Mullerornis'' nominal species, making ''modestus'' the epithet of the ''Mullerornis'' type species. However, later DNA studies found that ''Vorombe titan'' was indistinguishable from ''A. maximus'', and probably represented large females of the species.


Evolution

Like the
cassowaries Cassowaries (; Biak language, Biak: ''man suar'' ; ; Papuan_languages, Papuan: ''kasu weri'' ) are flightless birds of the genus ''Casuarius'', in the order Casuariiformes. They are classified as ratites, flightless birds without a keel (bird a ...
,
ostrich Ostriches are large flightless birds. Two living species are recognised, the common ostrich, native to large parts of sub-Saharan Africa, and the Somali ostrich, native to the Horn of Africa. They are the heaviest and largest living birds, w ...
es, rheas,
emu The emu (; ''Dromaius novaehollandiae'') is a species of flightless bird endemism, endemic to Australia, where it is the Tallest extant birds, tallest native bird. It is the only extant taxon, extant member of the genus ''Dromaius'' and the ...
and kiwis, the Elephant bird was a
ratite Ratites () are a polyphyletic group consisting of all birds within the infraclass Palaeognathae that lack keels and cannot fly. They are mostly large, long-necked, and long-legged, the exception being the kiwi, which is also the only nocturnal ...
; it could not fly, and its breast bone had no
keel The keel is the bottom-most longitudinal structural element of a watercraft, important for stability. On some sailboats, it may have a fluid dynamics, hydrodynamic and counterbalancing purpose as well. The keel laying, laying of the keel is often ...
. Because Madagascar and Africa separated before the ratite lineage arose, ''Aepyornis'' and other elephant birds are thought to have dispersed and become flightless and gigantic ''
in situ is a Latin phrase meaning 'in place' or 'on site', derived from ' ('in') and ' ( ablative of ''situs'', ). The term typically refers to the examination or occurrence of a process within its original context, without relocation. The term is use ...
''. More recently, it has been deduced from DNA sequence comparisons that the closest living relatives of elephant birds are the
New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...
kiwis, from which they were estimated to have diverged over 50 million years ago.


Description

The species of ''Aepyornis'' are amongst the largest birds, with weights of estimated for ''A. hildebrandti'' and for ''A. maximus,'' making it one of the largest, if not the largest bird to have ever lived,'''' with the latter reaching in height. The head bore a straight, thick conical beak, which was proportionally larger in A. ''hildebrandti'' than in ''A. maximus'', though the heads in both birds were small relative to body size. The neck was proportionally long, with 17
cervical vertebrae In tetrapods, cervical vertebrae (: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In saurop ...
. The wings were vestigial. The pelvic bones (vertebrae, ilium and pubis) were heavily fused to each other, so much so that their boundaries are difficult to discern. The hindlimb was proportionally long, with its bones being robust, with the femur in particular being very short and thick. The
tibiotarsus The tibiotarsus is the large bone between the femur and the tarsometatarsus in the leg of a bird. It is the fusion of the proximal part of the tarsus with the tibia. A similar structure also occurred in the Mesozoic Heterodontosauridae. These ...
has a prominent longitudinal ridge for muscle attachment. There is no evidence for the presence of a fourth toe or spur. The terminal toe bones (phalanges) of the foot are broad and not hooked. The females of ''A. maximus'' are suggested to have been larger than the males, as is observed in other ratites.


Ecology

Examination of brain endocasts has shown that both ''A. maximus'' and ''A. hildebrandti'' had greatly reduced optic lobes, similar to those of their closest living relatives, the kiwis, and consistent with a similar
nocturnal Nocturnality is a ethology, behavior in some non-human animals characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnality, diurnal meaning the opposite. Nocturnal creatur ...
lifestyle. ''A. maximus'' had relatively larger
olfactory bulb The olfactory bulb (Latin: ''bulbus olfactorius'') is a neural structure of the vertebrate forebrain involved in olfaction, the sense of smell. It sends olfactory information to be further processed in the amygdala, the orbitofrontal cortex (OF ...
s than ''A. hildebrandti'', suggesting that the former occupied forested habitats where the sense of smell is more useful while the latter occupied open habitats. Elephant birds are suggested to have grown in periodic spurts rather than having continuous growth. A 2022 isotope analysis study suggested that individuals of ''Aepyornis'' ''hildebrandti'' from central Madagascar were mixed feeders that had a large (~48%)
grazing In agriculture, grazing is a method of animal husbandry whereby domestic livestock are allowed outdoors to free range (roam around) and consume wild vegetations in order to feed conversion ratio, convert the otherwise indigestible (by human diges ...
component to its diet, similar to that of the living ''
Rhea americana The greater rhea (''Rhea americana'') is a species of flightless bird native to eastern South America. Other names for the greater rhea include the grey, common, or American rhea; ema ( Portuguese); or ñandú ( Guaraní and Spanish). One of two ...
'', while ''A. maximus'' was probably a browser. Isotope analysis of eggshells attributed to a population of ''A. hildebrandti'' from northern Madagascar suggests that this population were probably browsers rather than mixed feeders. An embryonic skeleton of ''Aepyornis'' is known from an intact egg, around 80-90% of the way through incubation before it died. This skeleton shows that even at this early ontogenetic stage that the skeleton was robust, much more so than comparable hatchling ostriches or rheas. The eggs of ''Aepyornis'' are the largest known for any
amniote Amniotes are tetrapod vertebrate animals belonging to the clade Amniota, a large group that comprises the vast majority of living terrestrial animal, terrestrial and semiaquatic vertebrates. Amniotes evolution, evolved from amphibious Stem tet ...
, and have a volume of around 5.6–13 litres, and a length of approximately and a width of . The egg is about 160 times greater volume than a chicken egg.Hawkins, A. F. A. & Goodman, S. M. (2003) The large size of elephant bird eggs means that they would have required substantial amounts of calcium, which is usually taken from a reservoir in the
medullary bone The medullary cavity (''medulla'', innermost part) is the central cavity of bone shafts where red bone marrow and/or yellow bone marrow (adipose tissue) is stored; hence, the medullary cavity is also known as the marrow cavity. Located in the ma ...
in the femurs of female birds. Possible remnants of this tissue have been described from the femurs of ''A. maximus.''


Extinction

The extinction of ''Aepyornis'' was likely due to human activity, especially after the arrival of humans on Madagascar. The birds were initially widespread, occurring from the northern to the southern tip of Madagascar. One theory—the blitzkrieg hypothesis—contends that humans hunted the elephant birds to extinction in a very short time after their arrival. There is indeed evidence that they were killed. However, their eggs may have been the most vulnerable point in their life cycle. A recent archaeological study found fragments of eggshells among the remains of human fires,Pearson and Godden (2002) suggesting that the eggs regularly provided meals for entire families. The exact time period when they died out is also not certain; tales of these giant birds may have persisted for centuries in folk memory. There is archaeological evidence of Giant elephant bird (''A. maximus'') from a
radiocarbon-dated Radiocarbon dating (also referred to as carbon dating or carbon-14 dating) is a method for Chronological dating, determining the age of an object containing organic material by using the properties of carbon-14, radiocarbon, a radioactive Isotop ...
bone at 1880 +/- 70 BP () with signs of butchering, and on the basis of radiocarbon dating of shells, about 1000 BP (= ). It is thought that the ''A. maximus'' is the Malagasy legendary extinct animal called the ''vorompatra'' (pronounced ), Malagasy for "bird of open spaces”. After many years of failed attempts, DNA molecules of ''Aepyornis'' eggs were successfully extracted by a group of international researchers and results were published in 2010 in the ''Proceedings of the Royal Society B''. It has also been suggested that the extinction was a secondary effect of human impact due to transfer of hyperdiseases from human
commensal Commensalism is a long-term biological interaction (symbiosis) in which members of one species gain benefits while those of the other species neither benefit nor are harmed. This is in contrast with mutualism, in which both organisms benefit f ...
s, such as chickens and
guineafowl Guinea fowl () (or guineahen) are birds of the family Numididae in the order Galliformes. They are endemic to Africa and rank among the oldest of the gallinaceous birds. Phylogenetically, they branched off from the core Galliformes after the C ...
. The bones of these domesticated fowl have been found in
subfossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
sites on the island (MacPhee and Marx, 1997: 188), such as Ambolisatra (Madagascar), where ''Mullerornis'' ''modestus'' and ''A. maximus'' have been reported.Goodman, S. M. & Rakotozafy, L. M. A. (1997)


See also

*
Island gigantism Island gigantism, or insular gigantism, is a biological phenomenon in which the size of an animal species isolated on an island increases dramatically in comparison to its mainland relatives. Island gigantism is one aspect of the more general "is ...
* Æpyornis Island, a short story by H. G. Wells that features the bird.


Footnotes


References

* * * * * * * * * * * * * * * {{Taxonbar, from=Q2638301 Elephant birds Extinct animals of Madagascar