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18.12.2015 20:58 - Encyclopedia Largest prehistoric animals Vol.1 Vertebrates part2 Birds Ch.2 The bigest birds of all time - competitors
Автор: valentint Категория: Забавление   
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The next largest was Australian Dromornis stirtoni.
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Dromornis stirtoni was the largest of the dromornithids, a group of huge flightless birds known only from Australia. The late Miocene Dromornis, from Alcoota Station in the Northern Territory, weighed up to 500kg and stood over three metres in height, making it heavier than the Giant Moa of New Zealand and taller than the Elephant Bird of Madagascar.
Mihirungs were large, flightless birds with deep lower jaws, a distinctly shaped quadrate bone (connecting upper and lower jaws), stubby wings, massive hind legs and hoof-like toes. They lacked a keeled sternum (breastbone), a specialization related to the reduction of flight muscles.
Dromornis stirtoni was over three metres in height, and from 450-500 kilograms in weight.
Dromornis stirtoni is known only from Alcoota Station, central Northern Territory.
The closest relatives of dromornithids were once thought to be the flightless ratites (emus, ostriches, rheas and their kin) but it is now believed that dromornithids evolved from waterfowl (ducks, geese and their ancestors).
The Alcoota region was subtropical open woodland during the late Miocene.
There is a great deal of debate over the diet of dromornithids. Many palaeontologists are convinced they were herbivores (eating mainly tough-skinned fruits and seed pods), but others think at least some dromornithids may have eaten meat, based on the shape and size of their skulls and beaks. All dromornithids lack a hooked beak, as in raptors, and Genyornis newtoni, from the Pleistocene, had hoof-like rather than recurved claws on its feet. Both these features are herbivore-like, although the feet of the larger dromornithids are unknown. Analysis of eggshells (amino acid analysis) in Genyornis supports an herbivorous diet at least in this dromornithid. Genyornis has also been also found in large numbers in some deposits, unlike carnivores (at the top of the food chain, carnivores are generally very rare). Those holding the view that dromornithids were to some degree carnivorous cite the huge size of the beak ("a case of overdesign"). The skulls of the larger dromornithids (Bullockornis and Dromornis) had proportionately more massive beaks than other species, including Genyornis, and there may in fact have been a variety of dietary options for the relatively diverse dromornithids.
Biomechanical studies suggest that dromornithids may have been relatively fast runners. Their massive legs were well muscled, providing the necessary power in spite of their bulk.
There is little direct evidence for the lifestyle of dromornithids. Eggs of the Pleistocene Genyornis newtoni have been found in sand dune deposits, suggesting that it nested in these dunes.
Dromornis stirtoni is known only from Alcoota Station in the Northern Territory, which would have when Dromornis was alive. Entire skeletons of Dromornis have been found at Alcoota Station.
The oldest evidence of dromornithids in Australia may be an impression (a natural cast) of articulated foot bones found near Brisbane in Queensland, which is Eocene in age and therefore some of the oldest evidence for Australian birds. The foot is that of a large, ground-dwelling bird similar to the Pleistocene Genyornis newtoni, the last known dromornithid and only one known from a complete, articulated foot. Genyornis and the Redbank bird have similar proportions of the foot bones (e.g., phalanx I of digit II is longer and thinner than phalanx I of digit III) and lack processes for flexor tendons. However, the Redbank bird does not have the hoof-like toes that the swifter Genyornis possessed.
Once thought to be ratites (the group to which emus, cassowaries, rheas and ostriches belong), dromornithids are now believed to be either within Anseriformes (the duck/goose group) or just basal to it. Recent revisions of the taxonomy of other large, flightless birds place these taxa (Gastornithidae, the family to which Diatryma belongs, and the Miocene Brontornis from Patagonia) within Anseriformes. All of these large birds, including the dromornithids, have a short dentary symphysis and a dorsally directed pterygoid process on the quadrate, unusual features not related to flightlessness. This revision is still debated, although many feel that the general placement of at least dromornithids somewhere near the base of the anseriform radiation has merit.


Of almost the same size was
elephant birds
with genera Aepyornis of Madagascar.Both were about 3 m tall (10 ft). The elephant birds were up to 400 kg and Dromornis stirtoni was up to 500 kg in weight.

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The elephant birds, which were giant ratites native to Madagascar, have been extinct since at least the 17th century. Йtienne de Flacourt, a French governor of Madagascar in the 1640s and 1650s, mentions an ostrich-like bird said to inhabit unpopulated regions. In 1659, Flacourt wrote: "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." Marco Polo also mentioned hearing stories of very large birds during his journey to the East during the late 13th century. These accounts are today believed to describe elephant birds.Aepyornis, believed to have been more than 3 m (10 ft) tall and weighing perhaps in the range of 350 to 500 kg (770 to 1,100 lb),was at the time the world"s largest bird. Only the rather older species Dromornis stirtoni from Australia is known to rival it in size among the fossil record and is reported to have shared the same estimated upper weight, 500 kg (1,100 lb). Remains of Aepyornis adults and eggs have been found; in some cases the eggs have a circumference of more than 1 m (3.3 ft) and a length up to 34 cm (13 in), the largest type of bird egg ever found. The egg weighed about 10 kg (22 lb). The egg volume is about 160 times greater than that of a chicken egg.
Four species are usually accepted in the genus Aepyornis today; A. hildebrandti, A. gracilis, A. medius and A. maximus, but the validity of some is disputed, with numerous authors treating them all in just one species, A. maximus. Up to three species are generally included in Mullerornis.
Aepyornis maximus is commonly known as the "elephant bird", a term that apparently originated from Marco Polo"s account of the rukh in 1298, although he was apparently referring to an eagle-like bird strong enough to "seize an elephant with its talons".Sightings of eggs of elephant birds by sailors (e.g. text on the Fra Mauro map of 1467-69, if not attributable to ostriches) could also have been erroneously attributed to a giant raptor from Madagascar. The legend of the roc could also have originated from sightings of such a giant subfossil eagle related to the African crowned eagle, which has been described in the genus Stephanoaetus from Madagascar, being large enough to carry off large primates; today, lemurs still retain a fear of aerial predators such as these. Another might be the perception of ratites retaining neotenic features and thus being mistaken for enormous chicks of a presumably more massive bird.
The ancient Malagasy name for the bird is vorompatra, meaning "bird of the Ampatres". The Ampatres are today known as the Androy region of southern Madagascar.
Like the ostrich, rhea, cassowary, emu, kiwi and extinct moa, Mullerornis and Aepyornis were ratites; they could not fly, and their breast bones had no keel. Because Madagascar and Africa separated before the ratite lineage arose, Aepyornis has been thought to have dispersed and become flightless and gigantic in situ.
More recently, it has been deduced from DNA sequence comparisons that the closest living relatives of elephant birds are New Zealandkiwis. Elephant birds are actually part of the mid-Cenozoic Australian ratite radiation; their ancestors flew across the Indian Ocean well after Gondwana broke apart. The existence of possible flying palaeognaths in the Miocene such as Proapteryx further supports the view that ratites did not diversify in response to vicariance. Gondwana broke apart in the Cretaceous and their phylogenetic tree does not match the process of continental drift.
Claims of findings of "aepyornithid" egg remains on the eastern Canary Islands, if valid, would represent a major biogeographical enigma.These islands are not thought to have been connected to mainland Africa when elephant birds were alive. There is no indication that elephant birds evolved outside Madagascar, and today, the Canary Island eggshells are considered to belong to extinct North African birds that may not have been ratites (possibly Eremopezus/Psammornis, or even Pelagornithidae, prehistoric seabirds of immense size).
Two whole eggs have been found in dune deposits in southern Western Australia, one in the 1930s (the Scott River egg) and one in 1992 (the Cervantes egg); both have been identified as Aepyornis maximus rather than Genyornis. It is hypothesized that the eggs floated from Madagascar to Australia on the Antarctic Circumpolar Current. Evidence supporting this is the finding of two fresh penguin eggs that washed ashore on Western Australia but originated in the Kerguelen Islands, and an ostrich (Struthio camelus) egg found floating in the Timor Sea in the early 1990s.
Because there is no rainforestfossil record in Madagascar, it is not known for certain if there were species adapted to dense forest dwelling, like the cassowary in Australia and New Guinea today. However, some rainforest fruits with thick, highly sculptured endocarps, such as that of the currently undispersed and highly threatened forest coconut palm 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 louvelii and Satranala decussilvae), just like many cassowary-dispersed fruits.
Occasionally subfossil eggs are found intact.The National Geographic Society in Washington holds a specimen of an Aepyornis egg which was given to Luis Marden in 1967. The specimen is intact and contains the skeleton of the unborn bird. The Denver Museum of Nature and Science (Denver, Colorado) holds two intact eggs, one of which is currently on display. Another giant Aepyornis egg is on display at the Harvard Museum of Natural History in Cambridge, MA. A cast of the egg is preserved at the Grant Museum of Zoology at London University.
David Attenborough owns an almost complete eggshell, dating from 600–700 CE, which he pieced together from fragments that were given to him while making his 1961 BBC series Zoo Quest to Madagascar.In March 2011, the BBC broadcast the 60-minute documentary Attenborough and the Giant Egg, presented by Attenborough, about his personal scientific quest to discover the secrets of the elephant bird and its egg.
There is also an intact specimen of an elephant bird"s egg (contrasted with the eggs from other bird species, including a hummingbird"s) on display at the Delaware Museum of Natural History, just outside Wilmington, Delaware, USA, and another in the Natural History Museum, London.
The Melbourne Museum has two Aepyornis eggs. The first was acquired for Ј100 by Professor Frederick McCoy in June 1862, and is an intact example. In 1950 it was subjected to radiological examination, which revealed no traces of embryonic material. A second, side-blown Aepyornis egg was acquired at a later date.
The Western Foundation of Vertebrate Zoology, with one of the world"s largest collections of avian eggs, has seven Aepyornis egg specimens.
A specimen is also held by the science department at Stowe School in Buckinghamshire, UK.
In the collections of the department of geology at the Field Museum of Natural History in Chicago there is a complete, side-blown egg collected by P. A. Bjelde.
In April 2013 a specimen was sold at Christie"s in London for Ј66,675 The pre-sale estimate had been "more than $45,000".
It is widely believed that the extinction of Aepyornis was a result of human activity. The birds were initially widespread, occurring from the northern to the southern tip of Madagascar. One theory states that humans hunted the elephant birds to extinction in a very short time for such a large landmass (the blitzkrieg hypothesis). There is indeed evidence that they were hunted and their preferred habitats destroyed. Their eggs may have been particularly vulnerable. A recent archaeological study found remains of eggshells among the remains of human fires, 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 Aepyornis from a radiocarbon-dated bone at 1880 ± 70 BP (approximately 120 CE) with signs of butchering, and on the basis of radiocarbon dating of shells, about 1000 BP (approximately 1000 CE).
An alternative theory is that the extinction was a secondary effect of human impact resulting from transfer of hyperdiseases from human commensals such as chickens and guineafowl. The bones of these domesticated fowl have been found in subfossil sites in the island (MacPhee and Marx, 1997: 188), such as Ambolisatra (Madagascar), where Mullerornis sp. and Aepyornis maximus have been reported.Also reported by these authors, ratite remains have been found in west and south west Madagascar, at Belo-sur-Mer (A. medius, Mullerornis rudis), Bemafandry (M. agilis) and Lamboharana (Mullerornis sp.).


The tallest bird ever was the giant moa (Dinornis maximus) at 3.6 m (12 ft) tall.
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Dinornis may have been the tallest bird that ever lived, with the females of the largest species standing 3.6 m (12 ft) tall and one of the most massive, weighing 230–240 kg (510–530 lb) or 278 kg (613 lb) in various estimates. Feather remains are reddish brown and hair-like, and apparently covered most of the body except the lower legs and most of the head (plus a small portion of the neck below the head). The feet were large and powerful, and the birds had a long neck that allowed them to reach tall vegetation. In relation to its body, the head was small, with a pointed, short, flat and somewhat curved beak.
It has been long suspected that several species of moa constituted males and females, respectively. This has been confirmed by analysis for sex-specific genetic markers of DNA extracted from bone material.For example, prior to 2003 there were three species of Dinornis recognised: South Island giant moa (D. robustus ), North Island giant moa (D. novaezealandiae) and slender moa (D. struthioides). However, DNA showed that all D. struthioides were in fact males, and all D. robustus were females. Therefore the three species of Dinornis were reclassified as two species, one each formerly occurring on New Zealand"s North Island (D. novaezealandiae) and South Island (D. robustus ); robustus however, comprises three distinct genetic lineages and may eventually be classified as many species. Dinornis seems to have had the most pronounced sexual dimorphism of all moa, with females being up to 150% as tall and 280% as heavy as males.
Prior to the arrival of humans, giant moa had had an ecologically stable population in (what is now known as) New Zealand for at least 40,000 years. The giant moa, along with other moa genera, were wiped out by Polynesian settlers, who hunted it for food. All taxa in this genus were extinct by 1500 in New Zealand. It is reliably known that the Māori still hunted them at the beginning of the fifteenth century, driving them into pits and robbing their nests. Although some birds became extinct due to farming, for which the forests were cut and burned down and the ground was turned into arable land, the giant moa had been extinct for 300 years prior to the arrival of European settlers.


Pachystruthio dmanisensis
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Towering more than ten feet tall and weighing in at about 1,000 pounds, big bird Pachystruthio was a big deal. The animal, which weighed about as much as a male polar bear, roamed the Black Sea peninsula of Crimea. That’s thousands of miles — and across the equator — from the better-known avian giants.
The earliest members of the genus Homo outside of Africa may have hunted Pachystruthio. But it’s unclear whether they would have been successful. The researchers behind the find say, unlike Madagascar’s large but lumbering elephant birds, this big bird was fast.
The animal’s massive thighbone turned up in central Crimea’s Taurida Cave, a site discovered only last year during a road construction project. Initial excavations at the cave have revealed an entire ecosystem of ancient giant deer, bison, saber-toothed cats and several other animals.
Researchers calculated the animal’s size as comparable to that of the giant extinct birds of the Southern Hemisphere, including New Zealand’s moa and the elephant birds of Madagascar.
With an estimated weight of just over 450kg (about 990 pounds), Pachystruthio would have been about three times larger than today’s ostriches. The modern birds get up to about 150kg.
By contrast, the largest of the elephant birds weighed an estimated 650kg (1,430 pounds).
Unlike the femurs of elephant birds, however, Pachystruthio’s thighbone is more slender and similar to that of a modern ostrich. That suggests the big bird may have been more of a runner than elephant birds, which researchers now think foraged at night.
A more fleet-footed mega-ostrich makes sense for Pachystruthio. Madagascar’s elephant birds lived on an island with no significant threat of predation (until our species showed up, that is). Pachystruthio had no such luck. Other fossils found at Taurida Cave include saber-toothed cats, giant hyenas and giant cheetahs.
Researchers place the most likely age of Pachystruthio at 1.7 million-1.8 million years old. Although the Taurida Cave femur is the largest of any bird in the Northern Hemisphere, it’s got company, both in age and size.
The Taurida Pachystruthio fossil is likely about as old as two similar femurs found roughly 500 miles to the southeast in Dmanisi, a crucial paleontological site in the Republic of Georgia. The Dmanisi femurs are just a little smaller, at 380 and 385 mm compared with the 390-millimeter length of the Taurida thighbone (for Imperial system holdouts, that’s a range of 14.9-15.3 inches).
Dmanisi is home to the oldest hominin fossils outside of Africa, the earliest of which is about 1.87 million years old. Although formally classified as a subspecies of Homo erectus, the Dmanisi hominins remain somewhat of a riddle due to their unique mix of features.
The ages of fossils at both Dmanisi and Taurida suggest that early members of our genus shared territory with the big birds. It’s easy to imagine our distant ancestors collecting their eggs and shed feathers as resources. Early hominins may have even hunted them for meat — or at least sprinted in the same direction as the big birds while running from the ecosystem’s toothier members.

















 





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Автор: valentint
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