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Elephant bird

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Elephant birds
Temporal range:Quaternary
↓
Aepyornis maximusskeleton and egg
Scientific classificationEdit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Infraclass: Palaeognathae
Clade: Novaeratitae
Order: †Aepyornithiformes
Newton,1884[1]
Type species
†Aepyornis maximus
Hilaire,1851
Genera

Elephant birdsare extinctflightless birdsbelonging to theorderAepyornithiformesthat were native to the island ofMadagascar.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 genusMullerornis,and two inAepyornis.Aepyornis maximusis possibly the largest bird to have ever lived, with their eggs being the largest known for anyamniote.Elephant birds arepalaeognaths(whose flightless representatives are often known asratites), and their closest living relatives arekiwi(found only in New Zealand), suggesting that ratites did not diversify byvicarianceduring the breakup ofGondwanabut insteadconvergently evolvedflightlessness from ancestors that dispersed more recently by flying.

Discovery[edit]

Elephant birds have been extinct since at least the 17th century.Étienne de Flacourt,a French governor of Madagascar during the 1640s and 1650s, mentioned an ostrich-like bird, said to inhabit unpopulated regions, although it is unclear whether he was repeating folk tales from generations earlier. In 1659, Flacourt wrote of the "vouropatra – a large bird which haunts the Ampatres and lays eggs like the ostriches; so that the people of these places may not take it, it seeks the most lonely places."[2][3]There has been speculation, especially popular in the latter half of the 19th century, that the legendaryrocfrom the accounts ofMarco Polowas ultimately based on elephant birds, but this is disputed.[4]

Between 1830 and 1840, European travelers in Madagascar saw giant eggs and eggshells.[3]British observers were more willing to believe the accounts of giant birds and eggs because they knew of themoain New Zealand.[3]In 1851 the genusAepyornisand speciesA. maximuswere scientifically described in a paper presented to theParis Academy of SciencesbyIsidore Geoffroy Saint-Hilaire,based on bones and eggs recently obtained from the island, which resulted in wide coverage in the popular presses of the time, particularly due to their very large eggs.[4]

Two whole eggs have been found in dune deposits in southernWestern Australia,one in the 1930s (the Scott River egg) and one in 1992 (theCervantesegg); both have been identified asAepyornis maximusrather thanGenyornis newtoni,an extinct giant bird known from the Pleistocene of Australia. It is hypothesized that the eggs floated from Madagascar to Australia on theAntarctic Circumpolar Current.Evidence supporting this is the finding of two freshpenguineggs that washed ashore on Western Australia but may have originated in theKerguelen Islands,and anostrich eggfound floating in theTimor Seain the early 1990s.[5]

Taxonomy and biogeography[edit]

Mullerornis modestus
Aepyornis maximusrestoration

Like theostrich,rhea,cassowary,emu,kiwiand extinctmoa,elephant birds were ratites; they could not fly, and theirbreast boneshad nokeel.Because Madagascar andAfricaseparated before the ratitelineagearose,[6]elephant birds has been thought to have dispersed and become flightless and giganticin situ.[7]

More recently, it has been deduced from DNA sequence comparisons that the closest living relatives of elephant birds are New Zealandkiwi,[8]though the split between the two groups is deep, with the two lineages being estimated to have diverged from each other around 54 million years ago.[9]

Placement of Elephant birds within Palaeognathae, after:[10][11]

Paleognathae

Struthionidae(ostriches)

Rheidae(rheas)

Tinamidae(tinamou)

†Dinornithiformes(moa)

Apterygidae(kiwis)

†Aepyornithiformes(elephant birds)

Casuariiformes(emu, cassowary)

The ancestors of elephant birds are thought to have arrived in Madagascar well afterGondwanabroke apart. The existence of possible flyingpalaeognathaein the Miocene such asProapteryxfurther supports the view that ratites did not diversify in response tovicariance.Gondwana broke apart in the Cretaceous and their phylogenetic tree does not match the process ofcontinental drift.Madagascar has a notoriously poor Cenozoic terrestrial fossil record, with essentially no fossils between the end of the Cretaceous (Maevarano Formation) and the Late Pleistocene.[12]Complete mitochondrial genomes obtained from elephant birds eggshells suggest thatAepyornisandMullerornisare significantly genetically divergent from each other, with amolecular clockanalysis estimating the split around 27 million years ago.[9]

Species[edit]

Up to 10 or 11 species in the genusAepyornishave been described,[13]but the validity of many have been disputed, with numerous authors treating them all in just one species,A. maximus.Up to three species have been described inMullerornis.[14]Recent work has restricted the number of elephant bird species to three, with two inAepyornis,one inMullerornis.[15]

  • Order AepyornithiformesNewton 1884[AepyornithesNewton 1884][13]
    • GenusAepyornisGeoffroy Saint-Hilaire 1850[16](Synonym:VorombeHansford & Turvey 2018)
      • Aepyornis hildebrandtiBurckhardt,1893(Possibly divided into two subspecies[15])
      • Aepyornis maximusHilaire,1851
    • GenusMullerornisMilne-Edwards & Grandidier 1894
      • Mullerornis modestus(Milne-Edwards & Grandidier 1869) Hansford & Turvey 2018

All elephant birds are usually placed in the single family Aepyornithidae, but some authors suggestAepyornisandMullerornisshould be placed in separate families within the Aepyornithiformes, with the latter placed into Mullerornithidae.[15]

Description[edit]

Size ofAepyornis maximus(center, in purple) compared to a human, a common ostrich (Struthio camelus,second from right, in maroon), and several non-aviantheropoddinosaurs.Grid spacings are 1.0 m.

Elephant birds were large sized birds (the largest reaching 3 metres (9.8 ft) tall in normal standing posture) that had vestigial wings, long legs and necks, with small heads relative to body size, which bore straight, thick conical beaks that were not hooked. The tops of elephant bird skulls display punctuated marks, which may have been attachment sites for fleshy structures or head feathers.[17]Mullerornisis the smallest of the elephant birds, with a body mass of around 80 kilograms (180 lb),[15]with its skeleton much less robustly built thanAepyornis.[18]A. hildebrandtiis thought to have had a body mass of around 230–285 kilograms (507–628 lb).[15]Estimates of the body mass ofAepyornis maximusspan from around 275 kilograms (606 lb)[19]to 700–1,000 kilograms (1,500–2,200 lb)[15]making it one of the largest birds ever, alongsideDromornis stirtoniandPachystruthio dmanisensis.[20][21]Females ofA. maximusare suggested to have been larger than the males, as is observed in other ratites.[15]

Biology[edit]

Aepyornisskull

Examination of brainendocastshas shown that bothA. maximusandA. hildebrandtihad greatly reducedoptic lobes,similar to those of their closest living relatives, the kiwis, and consistent with a similarnocturnallifestyle. The optic lobes ofMullerorniswere also reduced, but to a lesser degree, suggestive of a nocturnal orcrepuscularlifestyle.A. maximushad relatively largerolfactory bulbsthanA. hildebrandti,suggesting that the former occupied forested habitats where the sense of smell is more useful while the latter occupied open habitats.[22]

Diet[edit]

Because there is norainforestfossilrecord in Madagascar, it is not known for certain if there were species adapted to dense forest dwelling, like thecassowaryinAustraliaandNew Guineatoday. However, some rainforest fruits with thick, highly sculpturedendocarps,such as that of the currently undispersed and highly threatened forestcoconutpalm (Voanioala gerardii), may have been adapted for passage through ratite guts, and the fruit of some palm species are indeed dark bluish-purple (e.g.,Ravenea louveliiandSatranala decussilvae), just like many cassowary-dispersed fruits.[23]A 2022 isotope analysis study suggested that some specimens ofAepyornishildebrandtiwere mixed feeders that had a large (~48%)grazingcomponent to their diets, similar to that of the livingRhea americana,while the other species (A. maximus,Mullerornis modestus) were probablybrowsers.[24]It has been suggested thatAepyornisstraightened its legs and brought its torso into an erect position in order to browse higher vegetation.[25]

Growth and reproduction[edit]

Elephant birds are suggested to have grown in periodic spurts rather than having continuous growth.[18]An embryonic skeleton ofAepyornisis 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,[26]which may suggest that hatchlings wereprecocial.[18]

The eggs ofAepyornisare the largest known for anyamniote,and have a volume of around 5.6–13 litres (12–27 US pt), a length of approximately 26–40 centimetres (10–16 in) and a width of 19–25 centimetres (7.5–9.8 in).[18]The largestAepyorniseggs are on average3.3 mm (1⁄8in) thick, with an estimated weight of approximately 10.5 kilograms (23 lb).[15]Eggs ofMullerorniswere much smaller, estimated to be only1.1 mm (3⁄64in) thick, with a weight of about 0.86 kilograms (1.9 lb).[15]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 ofA. maximus.[18]

  • Eggs of Aepyornis (top left) chicken (bottom left) moa (right) and ostrich (centre)
    Eggs ofAepyornis(top left) chicken (bottom left) moa (right) and ostrich (centre)
  • Elephant bird egg (far left, 1) in comparison to other eggs, including ostrich egg (centre, 3) and chicken egg (third from right, 6)
    Elephant bird egg (far left, 1) in comparison to other eggs, including ostrich egg (centre, 3) and chicken egg (third from right, 6)
  • Well preserved egg showing porous surface
    Well preserved egg showing porous surface
  • Egg of Aepyornis standing upright
    Egg ofAepyornisstanding upright

Extinction[edit]

It is widely believed that the extinction of elephant birds was a result of human activity. The birds were initially widespread, occurring from the northern to the southern tip ofMadagascar.[27]The late Holocene also witnessed the extinction of other Malagasy animals, including several species ofMalagasy hippopotamus,two species of giant tortoise (Aldabrachelys abruptaandAldabrachelys grandidieri), thegiant fossa,over a dozen species ofgiant lemurs,the aardvark-like animalPlesiorycteropus,and the crocodileVoay.[25]Several elephant bird bones with incisions have been dated to approximately 10,000 BC which some authors suggest are cut marks, which have been proposed as evidence of a long history of coexistence between elephant birds and humans;[28]however, these conclusions conflict with more commonly accepted evidence of a much shorter history of human presence on the island and remain controversial. The oldest securely dated evidence for humans on Madagascar dates to the mid-first millennium AD.[29]

A 2021 study suggested that elephant birds, along with the Malagasy hippopotamus species, became extinct in the interval 800-1050 AD (1150–900 yearsBefore Present), based on the timing of the latest radiocarbon dates. The timing of the youngest radiocarbon dates co-incided with major environmental alteration across Madagascar by humans changing forest into grassland, probably for cattlepastoralism,with the environmental change likely being induced by the use of fire. This reduction of forested area may have had cascade effects, like making elephant birds more likely to be encountered by hunters,[30]though there is little evidence of human hunting of elephant birds. Humans may have utilized elephant bird eggs. Introduced diseases (hyperdisease) have been proposed as a cause of extinction, but the plausibility for this is weakened due to the evidence of centuries of overlap between humans and elephant birds on Madagascar.[25]

See also[edit]

References[edit]

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  2. ^Etienne de Flacourt (1658).Histoire de la grande isle Madagascar.chez Alexandre Lesselin. p. 165.Retrieved21 May2013.
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  4. ^abBuffetaut, Eric (6 September 2019)."Early illustrations of Aepyornis eggs (1851–1887): from popular science to Marco Polo's roc bird".Anthropozoologica.54(1): 111.doi:10.5252/anthropozoologica2019v54a12.ISSN0761-3032.S2CID203423023.
  5. ^Long, J. A.; Vickers-Rich, P.; Hirsch, K.; et al. (1998)."The Cervantes egg: an early Malagasy tourist to Australia".Records of the Western Australian Museum.19(Part 1): 39–46.Retrieved24 April2014.
  6. ^Yoder, A. D. & Nowak, M. D. (2006)
  7. ^van Tuinen, M. et al. (1998)
  8. ^Mitchell, K. J.; Llamas, B.; Soubrier, J.; et al. (23 May 2014)."Ancient DNA reveals elephant birds and kiwi are sister taxa and clarifies ratite bird evolution"(PDF).Science.344(6186): 898–900.Bibcode:2014Sci...344..898M.doi:10.1126/science.1251981.hdl:2328/35953.PMID24855267.S2CID206555952.
  9. ^abGrealy, Alicia; Phillips, Matthew; Miller, Gifford; et al. (April 2017). "Eggshell palaeogenomics: Palaeognath evolutionary history revealed through ancient nuclear and mitochondrial DNA from Madagascan elephant bird (Aepyornis sp.) eggshell".Molecular Phylogenetics and Evolution.109:151–163.Bibcode:2017MolPE.109..151G.doi:10.1016/j.ympev.2017.01.005.PMID28089793.
  10. ^Takezaki, Naoko (1 June 2023). Holland, Barbara (ed.)."Effect of Different Types of Sequence Data on Palaeognath Phylogeny".Genome Biology and Evolution.15(6).doi:10.1093/gbe/evad092.ISSN1759-6653.PMC10262969.PMID37227001.
  11. ^Urantówka, Adam Dawid; Kroczak, Aleksandra; Mackiewicz, Paweł (December 2020)."New view on the organization and evolution of Palaeognathae mitogenomes poses the question on the ancestral gene rearrangement in Aves".BMC Genomics.21(1): 874.doi:10.1186/s12864-020-07284-5.ISSN1471-2164.PMC7720580.PMID33287726.
  12. ^Samonds, Karen E.; Zalmout, Iyad S.; Irwin, Mitchell T.; et al. (12 December 2009). "Eotheroides lambondrano, new middle Eocene seacow (Mammalia, Sirenia) from the Mahajanga Basin, northwestern Madagascar".Journal of Vertebrate Paleontology.29(4): 1233–1243.Bibcode:2009JVPal..29.1233S.doi:10.1671/039.029.0417.ISSN0272-4634.S2CID59466434.
  13. ^abBrodkorb, Pierce (1963)
  14. ^Davies, S. J. J. F. (2003)
  15. ^abcdefghiGrealy, Alicia; Miller, Gifford H.; Phillips, Matthew J.; Clarke, Simon J.; Fogel, Marilyn; Patalwala, Diana; Rigby, Paul; Hubbard, Alysia; Demarchi, Beatrice; Collins, Matthew; Mackie, Meaghan; Sakalauskaite, Jorune; Stiller, Josefin; Clarke, Julia A.; Legendre, Lucas J. (28 February 2023)."Molecular exploration of fossil eggshell uncovers hidden lineage of giant extinct bird".Nature Communications.14(1): 914.Bibcode:2023NatCo..14..914G.doi:10.1038/s41467-023-36405-3.ISSN2041-1723.PMC9974994.PMID36854679.
  16. ^Hume, Julian P.; Walters, Michael (2012).Extinct birds.T&AD Poyser. p. 544.ISBN978-1-4081-5861-6.
  17. ^Angst, Delphine; Buffetaut, Eric (2017),"Aepyornithiformes",Palaeobiology of Extinct Giant Flightless Birds,Elsevier, pp. 65–94,doi:10.1016/b978-1-78548-136-9.50003-9,ISBN978-1-78548-136-9,retrieved2 May2023
  18. ^abcdeChinsamy, Anusuya; Angst, Delphine; Canoville, Aurore; Göhlich, Ursula B (1 June 2020)."Bone histology yields insights into the biology of the extinct elephant birds (Aepyornithidae) from Madagascar".Biological Journal of the Linnean Society.130(2): 268–295.doi:10.1093/biolinnean/blaa013.ISSN0024-4066.
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  20. ^Handley, Warren D.; Chinsamy, Anusuya; Yates, Adam M.; Worthy, Trevor H. (2 September 2016)."Sexual dimorphism in the late Miocene mihirung Dromornis stirtoni (Aves: Dromornithidae) from the Alcoota Local Fauna of central Australia".Journal of Vertebrate Paleontology.36(5): e1180298.Bibcode:2016JVPal..36E0298H.doi:10.1080/02724634.2016.1180298.ISSN0272-4634.S2CID88784039.
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  28. ^Hansford, J.; Wright, P. C.; Rasoamiaramanana, A.; Pérez, V. R.; Godfrey, L. R.; Errickson, D.; Thompson, T.; Turvey, S. T. (2018)."Early Holocene human presence in Madagascar evidenced by exploitation of avian megafauna"(PDF).Science Advances.4(9): eaat6925.Bibcode:2018SciA....4.6925H.doi:10.1126/sciadv.aat6925.PMC6135541.PMID30214938.
  29. ^Mitchell, Peter (1 October 2020)."Settling Madagascar: When Did People First Colonize the World's Largest Island?".The Journal of Island and Coastal Archaeology.15(4): 576–595.doi:10.1080/15564894.2019.1582567.ISSN1556-4894.S2CID195555955.
  30. ^Hansford, James P.; Lister, Adrian M.; Weston, Eleanor M.; Turvey, Samuel T. (July 2021)."Simultaneous extinction of Madagascar's megaherbivores correlates with late Holocene human-caused landscape transformation".Quaternary Science Reviews.263:106996.Bibcode:2021QSRv..26306996H.doi:10.1016/j.quascirev.2021.106996.S2CID236313083.

Further reading[edit]

External links[edit]

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