63-771: 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. Its closest living relative is the New Zealand kiwi . They became extinct sometime around 1000 AD , probably as a result of human activity. 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 . The nominal species Aepyornis titan Andrews, 1894,
126-458: A crown group definition, Amniota has a slightly different content than the biological amniotes as defined by an apomorphy. Though traditionally considered reptiliomorphs, some recent research has recovered diadectomorphs as the sister group to Synapsida within Amniota, based on inner ear anatomy. The cladogram presented here illustrates the phylogeny (family tree) of amniotes, and follows
189-520: A molecular clock analysis estimating the split around 27 million years ago. Molecular dating estimates that the divergence between Aepyornithidae and Mullerornithidae occurred approximately 30 Ma, close to the Eocene-Oligocene boundary, a period of marked global cooling and faunal turnover in the Northern Hemisphere. Up to 10 or 11 species in the genus Aepyornis have been described, but
252-493: A calcified shell, were not essential and probably evolved later. It has been suggested that shelled terrestrial eggs without extraembryonic membranes could still not have been more than about 1 cm (0.4-inch) in diameter because of diffusion problems, like the inability to get rid of carbon dioxide if the egg was larger. The combination of small eggs and the absence of a larval stage, where posthatching growth occurs in anamniotic tetrapods before turning into juveniles, would limit
315-402: A fetus. The term originally described a bowl in which the blood of sacrificed animals was caught, and derived from ἀμνός ( amnos ), meaning "lamb". Zoologists characterize amniotes in part by embryonic development that includes the formation of several extensive membranes, the amnion , chorion , and allantois . Amniotes develop directly into a (typically) terrestrial form with limbs and
378-417: A large (~48%) grazing component to their diets, similar to that of the living Rhea americana , while the other species ( A. maximus , Mullerornis modestus ) were probably browsers . It has been suggested that Aepyornis straightened its legs and brought its torso into an erect position in order to browse higher vegetation. Some rainforest fruits with thick, highly sculptured endocarps , such as that of
441-627: A large group that comprises the vast majority of living terrestrial and semiaquatic vertebrates. Amniotes evolved from amphibious stem tetrapod ancestors during the Carboniferous period . Those of Amniota are defined as the smallest crown clade containing humans , the Greek tortoise , and the Nile crocodile . Amniotes are distinguished from the other living tetrapod clade — the non-amniote lissamphibians ( frogs , salamanders , and caecilians ) — by
504-548: A length of approximately 26–40 centimetres (10–16 in) and a width of 19–25 centimetres (7.5–9.8 in). The largest Aepyornis eggs are on average 3.3 mm ( 1 ⁄ 8 in) thick, with an estimated weight of approximately 10.5 kilograms (23 lb). Eggs of Mullerornis were much smaller, estimated to be only 1.1 mm ( 3 ⁄ 64 in) thick, with a weight of about 0.86 kilograms (1.9 lb). The large size of elephant bird eggs means that they would have required substantial amounts of calcium, which
567-482: A long history of coexistence between elephant birds and humans; 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. A 2021 study suggested that elephant birds, along with the Malagasy hippopotamus species, became extinct in
630-495: A similar nocturnal lifestyle. The optic lobes of Mullerornis were also reduced, but to a lesser degree, suggestive of a nocturnal or crepuscular 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. A 2022 isotope analysis study suggested that some specimens of Aepyornis hildebrandti were mixed feeders that had
693-434: A thick stratified epithelium (rather than first entering a feeding larval tadpole stage followed by metamorphosis , as amphibians do). In amniotes, the transition from a two-layered periderm to a cornified epithelium is triggered by thyroid hormone during embryonic development, rather than by metamorphosis. The unique embryonic features of amniotes may reflect specializations for eggs to survive drier environments; or
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#1733106714376756-398: 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 ). It is thought that the A. maximus
819-428: 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, which may suggest that hatchlings were precocial . The eggs of Aepyornis are the largest known for any amniote , and have a volume of around 5.6–13 litres (12–27 US pt),
882-421: 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. Amniote Amniotes are tetrapod vertebrate animals belonging to the clade Amniota ,
945-408: Is observed in other ratites. 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
1008-450: Is presented in simplified form below. With the advent of cladistics, other researchers have attempted to establish new classes, based on phylogeny , but disregarding the physiological and anatomical unity of the groups. Unlike Benton, for example, Jacques Gauthier and colleagues forwarded a definition of Amniota in 1988 as "the most recent common ancestor of extant mammals and reptiles, and all its descendants". As Gauthier makes use of
1071-568: Is the Malagasy legendary extinct animal called the vorompatra (pronounced [vuˈrumpə̥ʈʂ] ), 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
1134-416: Is the smallest of the elephant birds, with a body mass of around 80 kilograms (180 lb), with its skeleton much less robustly built than Aepyornis . A. hildebrandti is thought to have had a body mass of around 230–285 kilograms (507–628 lb). Estimates of the body mass of Aepyornis maximus span from around 275 kilograms (606 lb) to 700–1,000 kilograms (1,500–2,200 lb) making it one of
1197-460: 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. 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
1260-403: 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. 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 of Madagascar . The late Holocene also witnessed
1323-512: The Bashkirian age of the Late Carboniferous around 318 million years ago . This basal divergence within Amniota has also been dated by molecular studies at 310–329 Ma, or 312–330 Ma, and by a fossilized birth–death process study at 322–340 Ma. The term amniote comes from the amnion , which derives from Greek ἀμνίον ( amnion ), which denoted the membrane that surrounds
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#17331067143761386-624: The Kerguelen Islands , and an ostrich egg found floating in the Timor Sea in the early 1990s. Like the ostrich , rhea , cassowary , emu , kiwi and extinct moa , elephant birds were ratites; they could not fly, and their breast bones had no keel . Because Madagascar and Africa separated before the ratite lineage arose, elephant birds has been thought to have dispersed and become flightless and gigantic in situ . More recently, it has been deduced from DNA sequence comparisons that
1449-744: 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 (whose flightless representatives are often known as ratites ), and their closest living relatives are kiwi (found only in New Zealand), suggesting that ratites did not diversify by vicariance during
1512-473: The placenta . The ancestors of true amniotes, such as Casineria kiddi , which lived about 340 million years ago, evolved from amphibian reptiliomorphs and resembled small lizards. At the late Devonian mass extinction (360 million years ago), all known tetrapods were essentially aquatic and fish-like. Because the reptiliomorphs were already established 20 million years later when all their fishlike relatives were extinct, it appears they separated from
1575-430: The semiaquatic amphibians do. They have better homeostasis in drier environments, and more efficient non-aquatic gas exchange to power terrestrial locomotion , which is facilitated by their astragalus. Basal amniotes resembled small lizards and evolved from semiaquatic reptiliomorphs during the Carboniferous period. After the Carboniferous rainforest collapse , amniotes spread around Earth's land and became
1638-632: 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." There has been speculation, especially popular in the latter half of the 19th century, that the legendary roc from the accounts of Marco Polo was ultimately based on elephant birds, but this is disputed. Between 1830 and 1840, European travelers in Madagascar saw giant eggs and eggshells. British observers were more willing to believe
1701-692: The 1930s (the Scott River egg) and one in 1992 (the Cervantes egg); both have been identified as Aepyornis maximus rather than Genyornis newtoni , an extinct giant bird known from the Pleistocene of Australia. 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 may have originated in
1764-547: The Aepyornithiformes, with the latter placed into Mullerornithidae. 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. Mullerornis
1827-758: 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 . 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. Complete mitochondrial genomes obtained from elephant birds eggshells suggest that Aepyornis and Mullerornis are significantly genetically divergent from each other, with
1890-578: The accounts of giant birds and eggs because they knew of the moa in New Zealand. In 1851 the genus Aepyornis and species A. maximus were scientifically described in a paper presented to the Paris Academy of Sciences by Isidore 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. Two whole eggs have been found in dune deposits in southern Western Australia , one in
1953-490: The amnion and the fluid it secretes shields the embryo from environmental fluctuations, amniotes can reproduce on dry land by either laying shelled eggs (reptiles, birds and monotremes ) or nurturing fertilized eggs within the mother ( marsupial and placental mammals ). This distinguishes amniotes from anamniotes ( fish and amphibians) that have to spawn in aquatic environments . Most amniotes still require regular access to drinking water for rehydration, like
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2016-449: The amniote ancestors, the next major breakthrough appears to have involved a gradual replacement of the gelatinous coating covering the amphibian egg with a fibrous shell membrane. This allowed the egg to increase both its size and in the rate of gas exchange, permitting a larger, metabolically more active embryo to reach full development before hatching. Further developments, like extraembryonic membranes (amnion, chorion, and allantois) and
2079-462: The breakup of Gondwana but instead convergently evolved flightlessness from ancestors that dispersed more recently by flying. 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
2142-550: The class Reptilia is paraphyletic —it has given rise to two other classes not included in Reptilia. Most species described as microsaurs , formerly grouped in the extinct and prehistoric amphibian group lepospondyls , has been placed in the newer clade Recumbirostra , and shares many anatomical features with amniotes which indicates they were amniotes themselves. A different approach is adopted by writers who reject paraphyletic groupings. One such classification, by Michael Benton ,
2205-712: The closest living relatives of elephant birds are New Zealand kiwi , 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. Placement of Elephant birds within Palaeognathae, after: 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 after Gondwana broke apart. The existence of possible flying palaeognathae in
2268-482: The closest living relatives of elephant birds are the New Zealand kiwis, from which they were estimated to have diverged over 50 million years ago. The species of Aepyornis are amongst the largest birds, with weights of 235 kilograms (520 lb) estimated for A. hildebrandti 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, with
2331-552: The currently undispersed and highly threatened forest coconut palm ( Voanioala gerardii ), may have been adapted for passage through ratite guts and consumed by elephant birds, 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, suggesting that they too may have been eaten by elephant birds. Elephant birds are suggested to have grown in periodic spurts rather than having continuous growth. An embryonic skeleton of Aepyornis
2394-425: The development of three extraembryonic membranes ( amnion for embryonic protection, chorion for gas exchange , and allantois for metabolic waste disposal or storage), thicker and keratinized skin , costal respiration (breathing by expanding/constricting the rib cage ), the presence of adrenocortical and chromaffin tissues as a discrete pair of glands near their kidneys , more complex kidneys ,
2457-402: The diapsid line of descent. Post-cranial remains of amniotes can be identified from their labyrinthodont ancestors by their having at least two pairs of sacral ribs , a sternum in the pectoral girdle (some amniotes have lost it) and an astragalus bone in the ankle. Amniota was first formally described by the embryologist Ernst Haeckel in 1866 on the presence of the amnion , hence
2520-438: The dominant land vertebrates. They almost immediately diverged into two groups, namely the sauropsids (including all reptiles and birds ) and synapsids (including mammals and extinct ancestors like " pelycosaurs " and therapsids ). Among the earliest known crown group amniotes, the oldest known sauropsid is Hylonomus and the oldest known synapsid is Asaphestera , both of which are from Nova Scotia during
2583-400: The early amniotes resembled their amphibian ancestors in many respects, a key difference was the lack of an otic notch at the back margin of the skull roof . In their ancestors, this notch held a spiracle , an unnecessary structure in an animal without an aquatic larval stage. There are three main lines of amniotes, which may be distinguished by the structure of the skull and in particular
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2646-411: 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, suggesting that the eggs regularly provided meals for entire families. The exact time period when they died out
2709-415: The embryonic membrane. Evolution of the amniote egg required increased exchange of gases and wastes between the embryo and the atmosphere. Structures to permit these traits allowed further adaption that increased the feasible size of amniote eggs and enabled breeding in progressively drier habitats. The increased size of eggs permitted increase in size of offspring and consequently of adults. Further growth for
2772-494: The extinction of other Malagasy animals, including several species of Malagasy hippopotamus , two species of giant tortoise ( Aldabrachelys abrupta and Aldabrachelys grandidieri ), the giant fossa , over a dozen species of giant lemurs , the aardvark-like animal Plesiorycteropus , and the crocodile Voay . 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
2835-515: The increase in size and yolk content of eggs may have permitted, and coevolved with, direct development of the embryo to a large size. Features of amniotes evolved for survival on land include a sturdy but porous leathery or hard eggshell and an allantois that facilitates respiration while providing a reservoir for disposal of wastes. Their kidneys (metanephros) and large intestines are also well-suited to water retention. Most mammals do not lay eggs, but corresponding structures develop inside
2898-515: The interval 800-1050 AD (1150–900 years Before 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 cattle pastoralism , 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, though there
2961-409: The largest birds ever, alongside Dromornis stirtoni and Pachystruthio dmanisensis . Females of A. maximus are suggested to have been larger than the males, as is observed in other ratites. 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
3024-481: 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
3087-410: The latter, however, was limited by their position in the terrestrial food-chain , which was restricted to level three and below, with only invertebrates occupying level two. Amniotes would eventually experience adaptive radiations when some species evolved the ability to digest plants and new ecological niches opened up, permitting larger body-size for herbivores, omnivores and predators. While
3150-448: The name. A problem with this definition is that the trait ( apomorphy ) in question does not fossilize , and the status of fossil forms has to be inferred from other traits. Older classifications of the amniotes traditionally recognised three classes based on major traits and physiology : This rather orderly scheme is the one most commonly found in popular and basic scientific works. It has come under critique from cladistics , as
3213-408: The number of holes behind each eye. In anapsids , the ancestral condition, there are none; in synapsids (mammals and their extinct relatives) there is one; and in diapsids (including birds, crocodilians , squamates , and tuataras ), there are two. Turtles have secondarily lost their fenestrae, and were traditionally classified as anapsids because of this. Molecular testing firmly places them in
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#17331067143763276-455: The other tetrapods somewhere during Romer's gap , when the adult tetrapods became fully terrestrial (some forms would later become secondarily aquatic). The modest-sized ancestors of the amniotes laid their eggs in moist places, such as depressions under fallen logs or other suitable places in the Carboniferous swamps and forests; and dry conditions probably do not account for the emergence of
3339-457: The presence of an astragalus for better extremity range of motion , the diminished role of skin breathing , and the complete loss of metamorphosis , gills , and lateral lines . The presence of an amniotic buffer, of a water-impermeable skin , and of a robust, air-breathing, respiratory system , allow amniotes to live on land as true terrestrial animals . Amniotes have the ability to procreate without water bodies . Because
3402-429: 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 component to its diet, similar to that of the living Rhea americana , while A. maximus
3465-729: The size of the adults. This is supported by the fact that extant squamate species that lay eggs less than 1 cm in diameter have adults whose snout-vent length is less than 10 cm. The only way for the eggs to increase in size would be to develop new internal structures specialized for respiration and for waste products. As this happened, it would also affect how much the juveniles could grow before they reached adulthood. A similar pattern can be seen in modern amphibians. Frogs that have evolved terrestrial reproduction and direct development have both smaller adults and fewer and larger eggs compared to their relatives that still reproduce in water. Fish and amphibian eggs have only one inner membrane,
3528-480: The skeleton was robust, much more so than comparable hatchling ostriches or rheas. 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). The egg is about 160 times greater volume than a chicken egg. The large size of elephant bird eggs means that they would have required substantial amounts of calcium, which
3591-401: The soft shell. Indeed, many modern-day amniotes require moisture to keep their eggs from desiccating . Although some modern amphibians lay eggs on land, all amphibians lack advanced traits like an amnion. The amniotic egg formed through a series of evolutionary steps. After internal fertilization and the habit of laying eggs in terrestrial environments became a reproduction strategy amongst
3654-577: 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 in Mullerornis . Recent work has restricted the number of elephant bird species to three, with two in Aepyornis , one in Mullerornis . All elephant birds are usually placed in the single family Aepyornithidae, but some authors suggest Aepyornis and Mullerornis should be placed in separate families within
3717-441: 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 Mullerornis modestus and A. maximus have been reported. Elephant bird Elephant birds are extinct flightless birds belonging to
3780-564: Was indistinguishable from A. maximus , and probably represented large females of the species. Like the cassowaries , ostriches , rheas , emu and kiwis , the Elephant bird was a ratite ; it could not fly, and its breast bone had no keel . 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 . More recently, it has been deduced from DNA sequence comparisons that
3843-466: 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
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#17331067143763906-404: 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
3969-403: 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. The females of A. maximus are suggested to have been larger than the males, as
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