Aepyornis

Aepyornis Temporal range: Quaternary PreꞒ Ꞓ O S D C P T J K Pg N ↓
Aepyornis maximus skeleton and egg
Conservation status
Extinct  (1000 AD)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Infraclass:	Palaeognathae
Order:	† Aepyornithiformes
Genus:	† Aepyornis I. Geoffroy Saint-Hilaire, 1851 [1]
Type species
Aepyornis maximus I. Geoffroy Saint-Hilaire 1851
Species
A. hildebrandti Burckhardt 1893 [1] A. maximus I. Geoffroy Saint-Hilaire 1851 [1]
Map of Madagascar showing where A. hildebrandti (b) and A. maximus (c) specimens have been found
Synonyms
Vorombe? Hansford & Turvey, 2018

Aepyornis is an extinct genus of elephant bird formerly endemic to Madagascar. The genus had two species, the smaller A. hildebrandti and the larger A. maximus, which is possibly the largest bird ever to have lived. ^[2] Its closest living relative is the New Zealand kiwi. ^[3] They became extinct sometime around 1000 AD, probably as a result of human activity.

Contents

• Taxonomy
• Evolution
• Description
• Ecology
• Extinction
• See also
• Footnotes
• References

Taxonomy

Brodkorb (1963) listed four species of Aepyornis as valid: A. hildebrandti, A. gracilis, A. medius and A. maximus. ^[4] However, Hume and Walters (2012) listed only one species, A. maximus. ^[5] Most recently, Hansford and Turvey (2018) recognized only A. hildebrandti and A. maximus. ^[6]

Description

The skull

The foot bones
Both photographed at the National Museum of Natural History in Paris

The species of Aepyornis are amongst the largest birds, with weights of 235 kilograms (520 lb) estimated for A. hildebrandti ^[2] and 275–1,000 kilograms (610–2,200 lb) for A. maximus, making it one of the largest, if not the largest bird to have ever lived, ^{[10] [2]} with the latter reaching 3 metres (9.8 ft) 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. 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 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. ^[11] The females of A. maximus are suggested to have been larger than the males, as is observed in other ratites. ^[2]

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 lifestyle. A. maximus had relatively larger olfactory bulbs than A. hildebrandti, suggesting that the former occupied forested habitats where the sense of smell is more useful while the latter occupied open habitats. ^[12] Elephant birds are suggested to have grown in periodic spurts rather than having continuous growth. ^[13] A 2022 isotope analysis study suggested that individuals of Aepyornishildebrandti from central Madagascar were mixed feeders that had a large (~48%) grazing component to its diet, similar to that of the living Rhea americana , while A. maximus was probably a browser. ^[14] 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. ^[2]

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. ^[15] The eggs of Aepyornis are the largest known for any amniote, and have a volume of around 5.6–13 litres, and a length of approximately 26–40 centimetres (10–16 in) and a width of 19–25 centimetres (7.5–9.8 in). ^[13] The egg is about 160 times greater volume than a chicken egg. ^[16] 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 in the femurs of female birds. Possible remnants of this tissue have been described from the femurs of A. maximus. ^[13]

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. ^[16] 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, ^[17] 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 bone at 1880 +/- 70 BP (c. 120 AD) with signs of butchering, and on the basis of radiocarbon dating of shells, about 1000 BP (= c. 1000 AD). ^[16] It is thought that the A. maximus is the Malagasy legendary extinct animal called the vorompatra (pronounced [vuˈrumpə̥ʈʂ] ), Malagasy for "bird of open spaces. ^{[18] [19] [20]} 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. ^[21]

It has also been suggested that the extinction was a secondary effect of human impact due to transfer of hyperdiseases from human commensals, such as chickens and guineafowl. The bones of these domesticated fowl have been found in subfossil sites on the island (MacPhee and Marx, 1997: 188), such as Ambolisatra (Madagascar), where Mullerornismodestus and A. maximus have been reported. ^[22]

See also

• Island gigantism
• Æpyornis Island, a short story by H. G. Wells that features the bird.

Footnotes

Related Research Articles

Kiwi are flightless birds endemic to New Zealand of the order Apterygiformes. The five extant species fall into the family Apterygidae and genus Apteryx. Approximately the size of a domestic chicken, kiwi are the smallest ratites.

Moa are an extinct group of flightless birds formerly endemic to New Zealand. During the Late Pleistocene-Holocene, there were nine species. The two largest species, Dinornis robustus and Dinornis novaezelandiae, reached about 3.6 metres (12 ft) in height with neck outstretched, and weighed about 230 kilograms (510 lb) while the smallest, the bush moa, was around the size of a turkey. Estimates of the moa population when Polynesians settled New Zealand circa 1300 vary between 58,000 and approximately 2.5 million.

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 extant ratite.

Elephant birds are extinct flightless birds belonging to the order Aepyornithiformes that were native to the island of Madagascar. They are thought to have become extinct around 1000 AD, likely as a result of human activity. Elephant birds comprised three species, one in the genus Mullerornis, and two in Aepyornis.Aepyornis maximus is possibly the largest bird to have ever lived, with their eggs being the largest known for any amniote. Elephant birds are palaeognaths, and their closest living relatives are kiwi, suggesting that ratites did not diversify by vicariance during the breakup of Gondwana but instead convergently evolved flightlessness from ancestors that dispersed more recently by flying.

Flightless birds have, through evolution, lost the ability to fly. There are over 60 extant species, including the well-known ratites and penguins. The smallest flightless bird is the Inaccessible Island rail. The largest flightless bird, which is also the largest living bird in general, is the common ostrich.

Ostriches are large flightless birds. Two living species are recognised, the common ostrich, native to large areas of sub-Saharan Africa, and the Somali ostrich, native to the Horn of Africa.

Palaeognathae is an infraclass of birds, called paleognaths or palaeognaths, within the class Aves of the clade Archosauria. It is one of the two extant infraclasses of birds, the other being Neognathae, both of which form Neornithes. Palaeognathae contains five extant branches of flightless lineages, termed ratites, and one flying lineage, the Neotropic tinamous. There are 47 species of tinamous, five of kiwis (Apteryx), three of cassowaries (Casuarius), one of emus (Dromaius), two of rheas (Rhea) and two of ostriches (Struthio). Recent research has indicated that paleognaths are monophyletic but the traditional taxonomic split between flightless and flighted forms is incorrect; tinamous are within the ratite radiation, meaning flightlessness arose independently multiple times via parallel evolution.

The fauna of Madagascar is a part of the wildlife of Madagascar.

The narrow-striped mongoose is a member of the family Eupleridae endemic to Madagascar. It inhabits the western Madagascar succulent woodlands and northern Madagascar spiny thickets in western and southwestern Madagascar, where it lives from sea level to about 125 m (410 ft) between the Tsiribihina and Mangoky rivers. In Malagasy it is called bokiboky. It is the only species in genus Mungotictis.

Mullerornis modestus is an extinct species of elephant bird, and the only member of the genus Mullerornis.

Cryptoprocta spelea, also known as the giant fossa, is an extinct species of carnivore from Madagascar in the family Eupleridae which is most closely related to the mongooses and includes all Malagasy carnivorans.

The Malagasy crowned eagle, also known as the Madagascar crowned hawk-eagle, is an extinct large bird of prey endemic to Madagascar.

Voay is an extinct genus of crocodile from Madagascar that lived during the Late Pleistocene to Holocene, containing only one species, V. robustus. Numerous subfossils have been found, including complete skulls, noted for their distinctive pair of horns on the posterior, as well as vertebrae and osteoderms from such places as Ambolisatra and Antsirabe. The genus is thought to have become extinct relatively recently. It has been suggested to have disappeared in the extinction event that wiped out much of the endemic megafauna on Madagascar, such as the elephant bird and Malagasy hippo, following the arrival of humans to Madagascar around 2000 years ago. Its name comes from the Malagasy word for crocodile.

Voalavo is a genus of rodent in the subfamily Nesomyinae, found only in Madagascar. Two species are known, both of which occur in mountain forest above 1250 m (4100 ft) altitude; the northern voalavo lives in northern Madagascar and eastern voalavo is restricted to a small area in the central part of the island. The genus was discovered in 1994 and formally described in 1998. Within Nesomyinae, it is most closely related to the genus Eliurus, and DNA sequence data suggest that the current definitions of these two genera need to be changed.

Hypogeomys australis is an extinct rodent from central and southeastern Madagascar. First described in 1903, it is larger than its close relative, the living Hypogeomys antimena, which occurs further west, but otherwise similar. Average length of the femur is 72.1 mm, compared to 63.8 mm in H. antimena. One of the few extinct rodents of Madagascar, it survived to at least around 1536 BP based on radiocarbon dating. Little is known of its ecology, but it may have lived in burrows like its living relative and eaten some arid-adapted plants.

Proapteryx micromeros is an extinct kiwi known from the 16–19 million-year-old early Miocene sediments of the St Bathans Fauna of Otago, New Zealand.

Notopalaeognathae is a clade that contains the order Rheiformes (rheas), the clade Novaeratitae, and the clade Dinocrypturi. Notopalaeognathae was named by Yuri et al. (2013) and defined by Sangster et al. (2022) as "the least inclusive crown clade containing Rhea americana, Tinamus major, and Apteryx australis". The exact relationships of this group, including its recently extinct members, have only recently been uncovered. The two lineages endemic to New Zealand, the kiwis and the extinct moas, are not each other's closest relatives: the moas are most closely related to the Neotropical tinamous, and the kiwis are sister to the extinct elephant birds of Madagascar, with kiwis and elephant birds together sister to the cassowaries and emu of New Guinea and Australia. The South American rheas are either sister to all other notopalaeognaths or sister to Novaeratitae. The sister group to Notopalaeognathae is Struthionidae.

References

Wikimedia Commons has media related to Aepyornis .

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