Gallimimus (/ˌɡælɪˈmaɪməs/ GAL-i-MY-məs) is a genus of theropod dinosaur that lived in what is now Mongolia during the Late Cretaceous period, about 70 million years ago (mya). Gallimimus is the largest known ornithomimid; adults were about 6 metres (20ft) long, 1.9 metres (6ft 3in) tall at the hip and weighed about 440 kilograms (970lb). As evidenced by its relative Ornithomimus, it would have had feathers. The head was small and light with large eyes that faced to the sides. The snout was long compared to other ornithomimids, although it was broader and more rounded at the tip than in other species. Gallimimus was toothless with a keratinous (horny) beak, and had a delicate lower jaw. Many of the vertebrae had openings that indicate they were pneumatic (air-filled). The neck was proportionally long in relation to the trunk. The hands were proportionally the shortest of any ornithomimosaur and each had three digits with curved claws. The forelimbs were weak while the hindlimbs were proportionally long.
Several fossils in various stages of growth were discovered by Polish-Mongolian expeditions in the Gobi Desert of Mongolia during the 1960s; a large skeleton discovered in this region was made the holotype specimen of the new genus and species Gallimimus bullatus in 1972. The generic name means "chicken mimic", referring to the similarities between its neck vertebrae and those of the Galliformes. The specific name is derived from bulla, a gold capsule worn by Roman youth, in reference to a bulbous structure at the base of the skull of Gallimimus. At the time it was named, the fossils of Gallimimus represented the most complete and best preserved ornithomimid material yet discovered, and the genus remains one of the best known members of the group. The family Ornithomimidae is part of the group Ornithomimosauria, the "ostrich dinosaurs". Anserimimus, also from Mongolia, is thought to have been the closest relative of Gallimimus.
As an ornithomimid, Gallimimus would have been a fleet (or cursorial) animal, using its speed to escape predators; its speed has been estimated at 42-56 km/h (29-34 mph). It may have had good vision and intelligence comparable to ratite birds. Gallimimus may have lived in groups, based on the discovery of several specimens preserved in a bone bed. Various theories have been proposed regarding the diet of Gallimimus and other ornithomimids. The highly mobile neck may have helped locate small prey on the ground, but it may also have been an opportunistic omnivore. It has also been suggested that it used small columnar structures in its beak for filter-feeding in water, though these structures may instead have been ridges used for feeding on tough plant material, indicative of a herbivorous diet. Gallimimus is the most commonly found ornithomimosaur in the Nemegt Formation, where it lived alongside its relatives Anserimimus and Deinocheirus. Gallimimus was featured in the movie Jurassic Park, in a scene that was important to the history of special effects, and in shaping the common conception of dinosaurs as bird-like animals.
Description

Gallimimus is the largest known member of the family Ornithomimidae. The adult holotype (specimen IGM 100/11) was about 6 metres (20ft) long and 1.9 metres (6.2ft) tall at the hip; its skull was 330 millimetres (1.08ft) long and the femur (thigh bone) was 660 millimetres (2.17ft). It would have weighed about 440 kilograms (970lb). In comparison, one juvenile specimen (ZPAL MgD-I/94) was about 2.15 metres (7.1ft) long, 0.79 metres (2.6ft) tall at the hip, and weighed about 26 kilograms (57lb).[1] Based on fossils of the related Ornithomimus, it is known that ornithomimosaurs were feathered, and that the adults bore wing-like structures as evidenced by the presence of quill-knobs on the ulna bone of the lower arm, bumps that indicate where feathers would have attached.[2]
Skull

The head of Gallimimus was very small and light compared to the vertebral column. Due to the length of its snout, the skull was long compared to other ornithomimids, and the snout had a gently sloping upper profile; this was less distinct in juvenile specimens. The side profile of the snout differed from other ornithomimids in not narrowing towards its front half, and the lower front margin of the premaxilla at the front of the upper jaw rose upwards, instead of being horizontal. Seen from above, the snout was almost spatulate (spoon-shaped), broad and rounded at the tip (or U-shaped), whereas it was acute (or V-shaped) in North American ornithomimids. The orbits (eye sockets) were large and faced sideways, as in other ornithomimids. The temporal region at the side of the skull behind the eyes was deep, and the infratemporal fenestra (the lower opening behind the orbit) was nearly triangular and smaller than that of the related Struthiomimus. It had deep muscle scars at the back part of the skull roof, along the parietal bone. The parasphenoid (a bone at the underside of the skull's base) was thin-walled, hollow and formed a pear-shaped, bulbous structure. The structure had a shallow furrow which opened at the base of the skull. The internal nares (internal openings for the nasal passage) were large and placed far back on the palate, due to the presence of an extensive secondary palate, which was common to ornithomimids.[3][4][5][6]
The delicate lower jaw, consisting of thin bones, was slender and shallow at the front, deepening towards the rear. The front of the mandible was shovel-like, resulting in a gap between the tips of the jaws when shut. The shovel-like shape was similar to that of the common seagull, and the lower beak may have had a shape similar to that of this bird. The retroarticular process at the back of the jaw (where jaw muscles attached) was well developed and consisted mainly of the angular bone. The surangular was the largest bone of the lower jaw, which is usual in theropods. The mandibular fenestra, a sidewards-facing opening in the lower jaw, was elongated and comparatively small. The lower jaw did not have a coronoid process or a supradentary bone, the lack of which is a common feature of beaked theropods (ornithomimosaurs, oviraptorosaurs, therizinosaurs and birds), but unusual among theropods in general. The shape and proportions of the skull changed significantly during growth. The rear of the skull and the orbits decreased in size, whereas the snout became relatively longer, similar changes occur in modern crocodiles. The skull was also proportionally larger in the younger specimens.[3][7] The jaws of Gallimimus were edentulous (toothless), and the front part would have been covered in a keratinous rhamphotheca (horny beak) in life. The beak may have covered a smaller area than in North American relatives, based on the lack of nourishing foramina on the maxilla. The inner side of the beak had small, tightly packed and evenly spaced columnar structures (their exact nature is debated), which were longest at the front and shortening towards the back.[5][7][8]
Postcranial skeleton

Gallimimus had 64–66 vertebrae in its spine, fewer than other ornithomimids. The centra (or bodies) of the vertebrae were platycoelous, with a flat front surface and a concave hind surface, except for the first six caudal (tail) vertebra–where the hind surface was also flat–and those at the end of the tail–which were amphiplatyan with both surfaces flat. Many of the centra had foramina (openings which have also been called "pleurocoels"), and were therefore probably pneumatic (with their hollow chambers invaded by air sacs). The neck consisted of 10 cervical vertebrae, which were all long and wide, except for the atlas bone (the first vertebra that connects with the back of the skull). The atlas differed from that of other ornithomimids in that the surface of its intercentrum was slanted downwards towards the back, instead of being concave and facing upwards. The neck appears to have been proportionally longer in relation to the trunk than in other ornithomimids. The neck was divided into two distinct sections: the cervical vertebrae at the front had centra which were nearly triangular in side view and tapered towards the back, as well as low neural arches and short, broad zygapophyses (the processes that articulated between the vertebrae); the cervical vertebrae at the back had spool-like centra which became gradually higher, and long, thin zygapophyses. The pneumatic foramina here were small and oval, and the neural spines projecting outwards from the centra formed long, low and sharp ridges, except for in the hindmost cervical vertebrae.[3][9]
The back of Gallimimus had 13 dorsal vertebrae, with spool-like centra that were short, but tended to become deeper and longer towards the back. Their transverse processes (processes articulating with the ribs) slightly increased in length towards the back. The two first dorsal centra had deep pneumatic foramina, while the rest only had shallow fossae (depressions), and the neural spines were prominent being somewhat triangular or rectangular in shape. The sacrum (fused vertebrae between the pelvic bones) consisted of five sacral vertebrae which were about equal in length. The centra here were spool-like, flattened sideways and had fossae which appear to have continued as deep foramina in some specimens. The neural spines here were rectangular, broad, and higher than those in the dorsal vertebrae. They were higher or equal in height to the upper margin of the iliac blade and were separate, whereas in other ornithomimids they were fused together. The tail had 36–39 caudal vertebrae with the centra of those at the front being spool-shaped, while those at the back were nearly triangular, and elongated across. The neural spines here were high and flat, but diminished backwards, where they became ridge-like. The only sign of pneumaticity in the tail were deep fossae between the neural spies and the transverse process of the two first caudal vertebrae. All the vertebrae in front of the sacrum bore ribs except for the atlas and the last dorsal vertebra. The ribs in the neck were fused to the vertebrae only in adults.[3][9]

The scapula (shoulder blade) was short and curved, thin at the front end, and thick at the back. It was connected relatively weakly with the coracoid, which was large and deep from top to bottom. Overall, the forelimbs did not differ much from those of other ornithomimids, all of which were comparatively weak. The humerus (upper arm bone), which had a near circular cross-section, was long and twisted. The deltopectoral crest on the upper front part of the humerus was comparatively small, and therefore provided little surface for attachment of upper arm muscles. The ulna was slender, long and weakly curved, with a nearly triangular shaft. The olecranon (the projection from the elbow) was prominent in adults, but not well developed in juveniles. The radius (the other bone in the lower arm) was long and slender with a more expanded upper end compared to the lower. The manus (hand) was proportionally short compared to those of other ornithomimosaurs, having the smallest manus to humerus length ratio of any member of the group, but was otherwise similar in structure. It had three fingers, which were similarly developed; the first (the "thumb") was the strongest, the third was the weakest and the second was the longest. The unguals (claw bones) were strong, somewhat curved (that of the first finger was most curved) and compressed sideways with a deep groove on each side. The unguals were similarly developed, though the third was slightly smaller. The forelimbs appear to have become proportionally longer during growth.[3][10][4]
The pubis (pubic bone) was long and slender, ending in a pubic boot which expanded to the front and back, a general feature of ornithomimosaurs. The hind limbs differed little from those of other ornithomimids, and were proportionally longer than in other theropods. The femur was nearly straight, long and slender, with a sideways flattened shaft. The tibia was straight, long, with two well developed condyles (rounded end of a bone) on the upper end and a flattened lower end. The fibula of the lower leg was flat, thin and broad at the upper end narrowing towards the lower end. The lower half of the third metatarsal was broad when viewed end on, partly covering the adjoining two metatarsals to each side, but narrowed abruptly at mid-length, wedging between those bones and disappearing (an arctometatarsalian foot structure). The third toe was proportionally shorter in relation to the limb than in other ornithomimids. As in other ornithomimids, the foot had no hallux (or dewclaw, the first toe of most other theropods). The unguals of the toes were flat on their lower sides; the outer two declined slightly outwards from their digits. The proportional length of the bones in the hind limbs changed very little with growth.[3][4]
History of discovery

Between 1963 and 1965, the Polish Academy of Sciences and the Mongolian Academy of Sciences organised the Polish-Mongolian palaeontological expeditions to the Gobi Desert of Mongolia. Among the dinosaur remains discovered in sand beds of the Nemegt Basin were numerous ornithomimids at different growth stages from the Nemegt, Tsaagan Khushuu, Altan Ula IV and Naran Bulak localities. Three partially complete skeletons, two with skulls, as well as many fragmentary remains, were collected. The largest skeleton (later to become the holotype of Gallimimus bullatus) was discovered by palaeontologist Zofia Kielan-Jaworowska in Tsaagan Khushuu in 1964; it was preserved lying on its back, and the skull was found under its pelvis. One small specimen was also found in Tsaagan Khushuu the same year, and another small specimen was found in the Nemegt locality. A small skeleton without forelimbs was discovered in 1967 by the Mongolian palaeontological expedition in Bugeen Tsav outside the Nemegt Basin. The fossils were housed at the Mongolian, Polish and USSR Academy of Sciences.[3][11][12] The Polish-Mongolian expeditions were notable for being led by women, some of which were among the first women to name new dinosaurs. The fossils discovered in these expeditions shed new light on the interchange of fauna between Asia and North America during the Cretaceous period.[13][14][15] Some of the skeletons were exhibited in Warsaw in 1968, mounted in tall, semi-erect postures, which was accepted at the time, though more horizontal postures are favoured today.[15]

In 1972, palaeontologists Halszka Osmólska, Ewa Roniewicz and Rinchen Barsbold named the new genus and species Gallimimus bullatus, using the largest collected skeleton, specimen IGM 100/11 (from Tsaagan Khushuu, formerly referred to as G.I.No.DPS 100/11 and MPD 100/11), as the holotype. The generic name is derived from the Latin gallus, "chicken", and the Greek mimos, "mimic", in reference to the front part of the neck vertebrae which resembled those of the Galliformes. The specific name is derived from the Latin bulla, a gold capsule worn by Roman youth around the neck, in reference to the bulbous capsule on the parasphenoid at the base of the dinosaur's skull. Such a feature had not been described from other reptiles at the time, and was considered unusual. The holotype consists of an almost complete skeleton with a distorted snout, incomplete lower jaw, vertebral series, pelvis, as well as some missing hand and foot bones.[3][16] The other partially complete skeletons were juveniles; ZPAL MgD-I/1 (from Tsaagan Khushuu) has a crushed skull with a missing tip, damaged vertebrae, fragmented ribs, pectoral girdle and forelimbs, and an incomplete left hind limb, ZPAL MgD-I/94 (from the Nemegt locality) lacks the skull, atlas, tip of the tail, pectoral girdle and forelimbs, while the smallest specimen, IGM 100/10 (from Bugeen Tsav), lacks a pectoral girdle, forelimbs and several vertebrae and ribs. Osmólska and colleagues listed 25 known specimens in all, 9 of which were only represented by single bones.[3][10]
At the time it was named, the fossils of Gallimimus represented the most complete and best preserved ornithomimid material yet discovered, and the genus remains one of the best known members of the group. Ornithomimids were previously known mainly from North America, Archaeornithomimus being the only prior known member from Asia (though without a skull). Since the first discoveries, more specimens have been found by further Mongolian-led international expeditions.[3][10][14][15] Three of the Gallimimus skeletons (including the holotype) later became part of a travelling exhibit of Mongolian dinosaur fossils, which toured various countries.[17][18] Fossil poaching has become a serious problem in Mongolia in the 21st century, and several Gallimimus specimens have been looted. In 2017, Hang-Jae Lee and colleagues reported a fossil trackway discovered in 2009 associated with a clenched Gallimimus foot (specimen MPC-D100F/17). The rest of the skeleton appeared to have been removed previously by poachers, along with several other Gallimimus specimens (as indicated by empty excavation pits, garbage, and scattered broken bones in the quarry). It is unusual to find tracks closely associated with body fossils; some of the tracks are consistent with ornithoimimid feet, while others belong to different dinosaurs.[19][20]

In 1988, the palaeontologist Gregory S. Paul concluded that the skulls of ornithomimids were more similar to each other than previously thought and moved most species into the same genus, Ornithomimus, resulting in the new combination O. bullatus.[1] In 2010, he instead listed it as "Gallimimus (or Struthiomimus) bullatus", but returned to using only the genus name Gallimimus in 2016.[21][22] The species involved have generally been kept in separate genera by other writers.[4] An ornithomimid vertebra from Japan informally named "Sanchusaurus" was reported in a 1988 magazine, but was assigned to Gallimimus sp. (of uncertain species) by the palaeontologist Dong Zhiming and colleagues in 1990.[16] Barsbold informally referred to a nearly complete skeleton (IGM 100/14) as "Gallimimus mongoliensis", but since it differs from Gallimimus in some details, Yoshitsugu Kobayashi and Barsbold proposed in 2006 that it probably belongs to a different genus. In 2000, the palaeontologist Philip J. Currie proposed that Anserimimus, which is only known from one skeleton from Mongolia, was a junior synonym of Gallimimus, but this was dismissed by Kobayashi and Barsbold, who pointed out several differences between the two. Barsbold noted some morphological variation among newer Gallimimus specimens, though this has never been published.[10]
Classification
Osmólska and colleagues assigned Gallimimus to the family Ornithomimidae in 1972, with the North American Struthiomimus as the closest relative, while lamenting the fact that comparison between taxa was difficult because other ornithomimids known at the time were either poorly preserved or inadequately described.[3] In 1975, Kielan-Jaworowska stated that though many dinosaurs from Asia were placed in the same families as North American relatives, this category of classification tended to be more inclusive than was used for modern birds. She highlighted that while Gallimimus had a rounded beak (similar to a goose or duck), North American ornithomimids had pointed beaks, a difference that would otherwise lead taxonomists to place modern birds in different families.[14] In 1976, Barsbold placed Ornithomimidae in the new group Ornithomimosauria (the "ostrich dinosaurs"). In 2003, Kobayashi and Jun-Chang Lü found that Anserimimus was the sister taxon to Gallimimus, both forming a derived (or "advanced") clade with North American genera, which was confirmed by Kobayashi and Barsbold in 2006.[10][5]
The following cladogram shows the placement of Gallimimus among Ornithomimidae according to Li Xu and colleagues, 2011:[23]

Ornithomimidae

Archaeornithomimusunnamed

Sinornithomimusunnamed

Anserimimus
Gallimimusunnamed

Qiupalongunnamed

Struthiomimus
Ornithomimus
Ornithomimosaurs belonged to the clade Maniraptoriformes of coelurosaurian theropods, which also includes modern birds. Early ornithomimosaurs had teeth, which were lost in more derived members of the group.[24] In 2004, Makovicky, Kobayashi, and Currie suggested that most of the early evolutionary history of ornithomimosaurs took place in Asia, where most genera have been discovered, including the most basal (or "primitive") taxa, although they acknowledged that the presence of the basal Pelecanimimus in Europe presents a complication in classification. The group must have dispersed once or twice from Asia to North America across Beringia to account for the Late Cretaceous genera found there. As seen in some other dinosaur groups, ornithomimosaurs were largely restricted to Asia and North America after Europe was separated from Asia by the Turgai Strait.[4]
In 1994, the palaeontologist Thomas R. Holtz grouped ornithomimosaurs and troodontids in a clade, based on shared features such as the presence of a bulbous capsule on the parasphenoid. He named the clade Bullatosauria, based on the specific name of Gallimimus bullatus, which was also in reference to the capsule.[25] In 1998, Holtz instead found that troodontids were basal maniraptorans, meaning that all members of that clade would fall within Bullatosauria, which would therefore become a junior synonym of Maniraptoriformes, and the clade has since fallen out of use.[26][27]
Palaeobiology

The cervical vertebrae of Gallimimus indicate that it held its neck obliquely, declining upwards at an angle of 35 degrees. Osmólska and colleagues found that the hands of Gallimimus were not prehensile (or capable of grasping), and that the thumb was not opposable. They also suggested that the arms were weak compared to, for example, those of the ornithomimosaur Deinocheirus. They agreed with the interpretations of ornithomimid biology by palaeontologist Dale Russell from earlier in 1972, including that they would have been very fleet (or cursorial) animals, although less agile than large, modern ground birds, and would have used their speed to escape predators. Russell also suggested that they had a good sense of vision and intelligence comparable to that of modern ratite birds. Since their predators may have had colour vision, he suggested it would have influenced their colouration, perhaps resulting in camouflage.[3][28] In 1982, palaeontologist Richard A. Thulborn estimated that Gallimimus could have run at speeds of 42-56 km/h (29-34 mph). He found that ornithimimids would not have been as fast as ostriches, which can reach 70-80 km/h (43-49 mph), in part due to their arms and tails increasing their weight.[29]

In 1988, Paul suggested that the eyeballs of ornithomimids were flattened and had minimal mobility within the sockets, necessitating movement of the head to view objects. Since their eyes faced more sideways  than in some other bird-like theropods, their binocular vision would have been more limited, which is an adaptation in some animals that improves their ability to see predators behind them. Paul considered the relatively short tails, which reduced weight, and missing halluxes of ornithomimids to be adaptations for speed. He suggested that they could have defended themselves by pecking and kicking, but would have mainly relied on their speed for escape.[1] In 2015, Akinobu Watanabe and colleagues found that together with Deinocheirus and Archaeornithomimus, Gallimimus had the most pneumatised skeleton among ornithomimosaurs. Pneumatisation is thought to be advantageous for flight in modern birds, but its function in non-avian dinosaurs is not known with certainty. It has been proposed that pneumatisation was used to reduce the mass of large bones, that it was related to high metabolism, balance during locomotion, or used for thermoregulation.[9]
In 2017, Lee and colleagues suggested various possible taphonomic circumstances (changes during decay and fossilisation) to explain how the Gallimimus foot discovered in 2009 was associated with a trackway. The trackway is preserved in sandstone while the foot is preserved in mudstone, extending 20 centimetres (7.9in) below the layer with the tracks. It is possible the fossil represents an animal that died in its tracks, but the depth of the foot in the mud may be too shallow for it to have become mired. It may also have been killed by a flood, after which it was buried in a pond. However, the layers of mud and sand do not indicate flooding but probably a dry environment, and the disrupted sediments around the fossil indicate the animal was alive when it came to the area. The authors thus suggested that the tracks had been made over an extended amount of time and period of drying, and that probably none of them were produced by the individual that owned the foot. The animal may have walked across the floor of a pond, breaking through the sediment layer with the tracks while it was soaked from rain or contained water. The animal may have died in this position from thirst, hunger, or another reason, and mud then deposited on the sand, thereby covering and preserving the tracks and the carcass. The foot may have become clenched and disarticulated as it decomposed, which made the tendons flex, and was later stepped on by heavy dinosaurs. The area may have been a single bone bed (based on the possible number of poached specimens) representing a Gallimimus mass mortality, perhaps due to a drought or famine. The fact that the animals seem to have died at the same time (the empty excavation pits were stratigraphically identical) may indicate that Gallimimus was gregarious (lived in groups), which has also been suggested for other ornithomimids.[20]
Development

A 1987 study by the biologists Roman Pawlicki and P. Bolechała showed age-related differences in the content of calcium and phosphorus (important components in the formation of bone) of Gallimimus specimens. They found that the ratio was highest in young to middle aged animals, decreasing with age.[30] In 1991, they reported that the bones of old individuals contained the highest amounts of lead and iron, while those in younger animals were lower.[31] A study of the bone histology of various dinosaurs in 2000, by biologists John M. Rensberger and Mahito Watabe, revealed that the canaliculi (channels which connect bone cells) and collagen fibre bundles of Gallimimus and other ornithomimids were more akin to those in birds than mammals, unlike those of ornithischian dinosaurs, which were more similar to mammals. These differences may have been related to the process and rate at which bone formed.[32] In 2012, palaeontologist Darla K. Zelenitsky and colleagues concluded that, since adult ornithomimosaurs had wing-like structures on their arms whereas juveniles did not (as evidenced by specimens of Ornithomimus), these structures were originally secondary sexual characteristics, which could have been used for reproductive behaviour such as courtship, display, and brooding.[2]
Feeding and diet

Osmólska and colleagues pointed out that the front part of the neck of Gallimimus would have been very mobile (the hind part was more rigid), the neural arches in the vertebrae of that region being similar to chicken and other Galliformes, indicating similar feeding habits. They found the beak of Gallimimus similar to that of a duck or goose, and that it would have fed on small, living prey which it swallowed whole. The mobility of the neck would have been useful in locating prey on the ground, since the eyes were positioned on the sides of the skull. They assumed that all ornithomimids had similar feeding habits, and pointed out that Russel had compared the beaks of ornithomimids with those of insectivorous birds. Osmólska and colleagues suggested that Gallimimus was capable of cranial kinesis (due to the seemingly loose connection between some of the bones at the back of the skull), a feature which allows individual bones of the skull to move in relation to each other. They also proposed that it did not use its short handed forelimbs for bringing food to the mouth, but for raking or digging in the ground to access food.[3] The hands of Gallimimus may have been weaker than for example those of Struthiomimus, which may instead have used its hands for hooking and gripping, according to a 1985 article by palaeontologists Elizabeth L. Nicholls and Anthony P. Russell.[33]
In 1988 Paul disagreed that ornithomimids were omnivores that ate small animals and eggs as well as plants, as had previously been suggested. He pointed out that ostriches and emus are mainly grazers and browsers, and that the skulls of ornithomimids were most similar to those of the extinct moas, which were strong enough to bite off twigs, as evidenced by their gut content. He further suggested that ornithomimids were well adapted for browsing on tough plants and would have used their hands to bring branches within reach of their jaws.[1] Palaeontologist Jørn Hurum suggested in 2001 that due to its similar jaw structure, Gallimimus may have had an opportunistic, omnivorous diet like seagulls. He also observed that the tight intramandibular joint would prevent any movement between the front and rear portions of the lower jaw.[7]

In 2001, palaeontologists Mark A. Norell, Makovicky, and Currie reported a Gallimimus skull (IGM 100/1133) and an Ornithomimus skull that preserved soft tissue structures on the beak. The inner side of the Gallimimus beak had columnar structures that the authors found similar to the lamellae in the beaks of anseriform birds, which use these for manipulating food, straining sediments, filter-feeding by segregating food items from other material, and for cutting plants while grazing. They found the Northern shoveller, which feeds on plants, molluscs, ostracods, and foraminiferans, to be the modern anseriform with structures most similar in anatomy to those of Gallimimus. The authors noted that ornithomimids probably did not use their beaks to prey on large animals and were abundant in mesic environments, while rarer in more arid environments, suggesting that they may have depended on aquatic food sources.[8] If this interpretation is correct, Gallimimus would have been one of the largest known terrestrial filter feeders.[4]
In 2005, palaeontologist Paul Barrett pointed out that the lamella-like structures of Gallimimus did not appear to have been flexible bristles like those of filter-feeding birds (as there is no indication of these structures overlapping or being collapsed), but were instead more akin to the thin, regularly spaced vertical ridges in the beaks of turtles and hadrosaurid dinosaurs. In these animals, such ridges are thought to be associated with herbivorous diets, used to crop tough vegetation. Barrett suggested that the ridges in the beak of Gallimimus represented a natural cast of the internal surface of the beak, indicating that the animal was a herbivore that fed on material high in fibre. The discovery of many gastroliths (gizzard stones) in some ornithomimids indicate the presence of a gastric mill, and therefore point towards a herbivorous diet, as these are used to grind food of animals that lack the necessary chewing apparatus. Barrett also calculated that a 440 kilograms (970lb) Gallimimus would have needed between 0.07 and 3.34 kilograms (0.15 and 7.36lb) of food per day, depending on whether it had an endothermic or an ectothermic ("warm" or "cold"-blooded) metabolism, an intake which he found to be unfeasible if it was a filter feeder. He also found that ornithomimids were abundant not only in formations that represented mesic environments, but also in arid environments where there would be insufficient water to sustain a diet based on filter feeding.[6] In 2007, palaeontologist Espen M. Knutsen wrote that the beak shape of ornithomimids, when compared to those of modern birds, was consistent with omnivory or high-fibre herbivory.[34]
Palaeoecology

Gallimimus is known from the Nemegt Formation in the Gobi Desert of southern Mongolia. This geologic formation has never been dated radiometrically, but the fauna present in the fossil record indicate it was probably deposited during the early Maastrichtian stage, at the end of the Late Cretaceous about 70 million years ago.[35][36][37] The sediments of the Gallimimus type locality Tsaagan Khushuu consist of silts, siltstones, mudstones, sands, as well as less frequent thin beds of sandstones.[12] The rock facies of the Nemegt Formation suggest the presence of river channels, mudflats, shallow lakes and floodplains in an environment similar to the Okavango Delta of present-day Botswana.[38] Large river channels and soil deposits are evidence of a significantly more humid climate than those found in the older Barun Goyot and Djadochta formations, although caliche deposits indicate that periodic droughts occurred.[39] Fossil bones from the Nemegt Basin, including of Gallimimus, are more radioactive than fossils from surrounding areas, possibly because uranium accumulated in the bones, transported there by percolating ground water.[15][40]
The Nemegt rivers, where Gallimimus lived, were home to a wide array of organisms. Occasional mollusc fossils, as well as a variety of other aquatic animals like fish, turtles,[35] and crocodylomorphs, including Shamosuchus, have been discovered in this region.[41] Mammal fossils are rare in the Nemegt Formation, but many birds, including the enantiornithine Gurilynia, the hesperornithiform Judinornis, as well as Teviornis, a possible anseriform, have been found. Herbivorous dinosaurs discovered in the Nemegt Formation include ankylosaurids such as Tarchia, the pachycephalosaurian Prenocephale, large hadrosaurids such as Saurolophus and Barsboldia, and sauropods such as Nemegtosaurus and Opisthocoelicaudia.[35][42] Predatory theropods that lived alongside Gallimimus include tyrannosauroids such as Tarbosaurus, Alioramus and Bagaraatan, and troodontids such as Borogovia, Tochisaurus and Zanabazar. Herbivorous or omnivorous theropods include therizinosaurs, such as Therizinosaurus, as well as oviraptorosaurians, such as Elmisaurus, Nemegtomaia, and Rinchenia.[43] Other ornithomimosaurs, including Anserimimus and Deinocheirus, are also found, but Gallimimus is the most common member of the group in the Nemegt.[10]
Cultural significance

Gallimimus was featured in the 1993 movie Jurassic Park by director Steven Spielberg; a similar scene in the original 1990 novel instead featured hadrosaurs. Spielberg had wanted a stampede sequence with animal herds in the movie, but did not know how to achieve it, and it was initially going to be visualised through stop-motion animation. At the time, there was little faith in creating animals through computer animation, but the visual effects company Industrial Light and Magic was given a go-ahead by the movie's producers to explore possibilities. ILM created a Gallimimus skeleton in the computer and animated a test showing a herd of running skeletons, and later a Tyrannosaurus chasing a fully rendered Gallimimus herd. The production team became very enthusiastic as nothing similar had previously been achieved, and Spielberg was convinced to write the scene into the script, and to also use computer graphics for other dinosaur shots in the movie instead of stop motion.[44][45] The Gallimimus were animated by tracing frames from footage of ostriches, and footage of herding gazelles was also referenced.[46] Kielan-Jaworowska, who discovered the holotype specimen, called it a "beautiful scene".[15] The movie's dinosaurs were one of the most widely publicised applications of computer-generated imagery in film, and were considered more lifelike than what had been previously accomplished with special effects.[47]
Emphasising the bird-like flocking behaviour of the Gallimimus herd was a point in Jurassic Park's story, as they were supposed to represent the precursors to birds. The herd was shown moving as a whole, rather than individual animals running around, and the smaller Gallimimus were shown in the middle of the group, as though they were protected.[44] During the scene, the protagonist palaeontologist Alan Grant says that the herd moves with "uniform direction changes, just like a flock of birds evading a predator" and "bet you'll never look at birds the same way again" as he watches the movements of the fast, graceful Gallimimus. This contrasted with how dinosaurs were traditionally depicted in mass media as lumbering, tail-dragging animals, and the movie helped change the common perception of dinosaurs. This and other scenes reflected then-recent theories of bird evolution encouraged by the movie's scientific advisor, palaeontologist John R. Horner, ideas which were still contentious at the time.[48][49][50] Despite such theories, Gallimimus and other dinosaurs of the movie were depicted without feathers, in part because it was unknown at the time how widespread these were among the group.[48][51]
It has been claimed that the Lark Quarry tracks (one of the world's largest concentrations of dinosaur tracks) in Queensland, Australia, served as inspiration and "scientific underpinning" for the Gallimimus stampede scene in Jurassic Park; these tracks were initially interpreted as representing a dinosaur stampede caused by the arrival of a theropod predator. The idea that the tracks represent a stampede has since been contested (the "theropod" may instead have been a herbivore similar to Muttaburrasaurus), and a consultant to Jurassic Park has denied the tracks served as inspiration for the movie.[52][53][54]
See also
Timeline of ornithomimosaur research
 Media related to Gallimimus at Wikimedia Commons


Blood fractionation is the process of fractionating whole blood, or separating it into its component parts.  This is typically done by centrifuging the blood.
The resulting components are:
a clear solution of blood plasma in the upper phase (which can be separated into its own fractions, see Blood plasma fractionation),
the buffy coat, which is a thin layer of leukocytes (white blood cells) mixed with platelets in the middle, and
erythrocytes (red blood cells) at the bottom of the centrifuge tube.
Serum separation tubes (SSTs) are tubes used in phlebotomy containing a silicone gel; when centrifuged the silicone gel forms a layer on top of the buffy coat, allowing the blood serum to be removed more effectively for testing and related purposes.
Plasma protein fractionation

Plasma proteins are separated by using the inherent differences of each protein. Fractionation involves changing the conditions of the pooled plasma (e.g., the temperature or the acidity) so that proteins that are normally dissolved in the plasma fluid become insoluble, forming large clumps, called precipitate. The insoluble protein can be collected by centrifugation. One of the very effective ways for carrying out this process is the addition of alcohol to the plasma membrane pool while simultaneously cooling the pool. This process is sometimes called cold alcohol fractionation or ethanol fractionation. It was described by and bears the eponym of Dr Edwin J. Cohn.  This procedure is carried out in a series of steps so that a single pool of plasma yields several different protein products, such as albumin and immune globulin.[1][2] Human serum albumin prepared by this process is used in some vaccines, for treating burn victims, and other medical applications.
See also
Blood plasma fractionation


Hagia Sophia (/ˈhɑːɡiə soʊˈfiːə/; from the Greek Αγία Σοφία, pronounced[aˈʝia soˈfia], "Holy Wisdom"; Latin: Sancta Sophia or Sancta Sapientia; Turkish: Ayasofya) is the former Greek Orthodox Christian patriarchal cathedral, later an Ottoman imperial mosque and now a museum (Ayasofya Müzesi) in Istanbul, Turkey. Built in 537 AD at the beginning of the Middle Ages, it was famous in particular for its massive dome. It was the world's largest building and an engineering marvel of its time. It is considered the epitome of Byzantine architecture[1] and is said to have "changed the history of architecture".[2]
The Hagia Sophia construction consists of mostly masonry. The structure is composed of brick and mortar joint that are 1.5 times the width of the bricks. The mortar joints are composed of a combination of sand and minute ceramic pieces displaced very evenly throughout the mortar joints. This combination of sand and ceramic pieces could be considered to be the equivalent of modern concrete at the time.[3]
From the date of its construction in 537 until 1453, it served as an Eastern Orthodox cathedral and the seat of the Ecumenical Patriarch of Constantinople,[4] except between 1204 and 1261, when it was converted by the Fourth Crusaders to a Roman Catholic cathedral under the Latin Empire. The building was later converted into an Ottoman mosque from 29 May 1453 until 1931. It was then secularized and opened as a museum on 1 February 1935.[5] It remained the world's largest cathedral for nearly a thousand years, until Seville Cathedral was completed in 1520.
The current building was originally constructed as a church between 532 and 537 on the orders of the Byzantine Emperor Justinian I and was the third Church of the Holy Wisdom to occupy the site, the prior one having been destroyed by rioters in the Nika Revolt. It was designed by the Greek geometers Isidore of Miletus and Anthemius of Tralles.[6] The church was dedicated to the Wisdom of God, the Logos, the second person of the Trinity,[7] its patronal feast taking place on 25 December, the commemoration of the birth of the incarnation of the Logos in Christ.[7] Although sometimes referred to as Sancta Sophia (as though it were named after Sophia the Martyr), sophia being the phonetic spelling in Latin of the Greek word for wisdom, its full name in Greek is Ναός της Αγίας του Θεού Σοφίας, Naos tēs Hagias tou Theou Sophias, "Shrine of the Holy Wisdom of God".[8][9] The church contained a large collection of relics and featured, among other things, a 15-metre (49ft) silver iconostasis. The focal point of the Eastern Orthodox Church for nearly one thousand years, the building witnessed the excommunication of Patriarch Michael I Cerularius officially communicated by Humbert of Silva Candida, the papal envoy of Pope Leo IX in 1054, an act that is commonly considered the start of the East–West Schism.
In 1453, Constantinople was conquered by the Ottoman Empire under Mehmed the Conqueror, who ordered this main church of Orthodox Christianity converted into a mosque. Although some parts of the city of Constantinople were falling into disrepair, the cathedral was maintained with an amount of money set aside for this purpose. Nevertheless, the Christian cathedral made a strong impression on the new Ottoman rulers and they decided to convert it into a mosque.[10][11] The bells, altar, iconostasis, and other relics were destroyed and the mosaics depicting Jesus, his Mother Mary, Christian saints, and angels were also destroyed or plastered over. Islamic features—such as the mihrab (a niche in the wall indicating the direction toward Mecca, for prayer), minbar (pulpit), and four minarets—were added. It remained a mosque until 1931 when it was closed to the public for four years. It was re-opened in 1935 as a museum by the Republic of Turkey. Hagia Sophia was, as of 2014, the second-most visited museum in Turkey, attracting almost 3.3 million visitors annually.[12] According to data released by the Turkish Culture and Tourism Ministry, Hagia Sophia was Turkey's most visited tourist attraction in 2015.[13]
From its initial conversion until the construction of the nearby Sultan Ahmed Mosque (Blue Mosque of Istanbul) in 1616, it was the principal mosque of Istanbul. The Byzantine architecture of the Hagia Sophia served as inspiration for many other Ottoman mosques, such as the aforementioned mosque, the Şehzade Mosque, the Süleymaniye Mosque, the Rüstem Pasha Mosque and the Kılıç Ali Pasha Complex.
History
Church of Constantius II
The first church on the site was known as the Μεγάλη Ἐκκλησία (Megálē Ekklēsíā, "Great Church"), or in Latin Magna Ecclesia,[14][15] because of its larger dimensions in comparison to the contemporary churches in the City.[7] Inaugurated on 15 February 360 (during the reign of Constantius II) by the Arian bishop Eudoxius of Antioch,[16] it was built next to the area where the imperial palace was being developed. The nearby Hagia Eirene ("Holy Peace") church was completed earlier and served as cathedral until the Great Church was completed. Both churches acted together as the principal churches of the Byzantine Empire.
Writing in 440, Socrates of Constantinople claimed that the church was built by Constantius II, who was working on it in 346.[16] A tradition which is not older than the 7th or 8th century, reports that the edifice was built by Constantine the Great.[16] Zonaras reconciles the two opinions, writing that Constantius had repaired the edifice consecrated by Eusebius of Nicomedia, after it had collapsed.[16] Since Eusebius was bishop of Constantinople from 339 to 341, and Constantine died in 337, it seems possible that the first church was erected by the latter.[16] The edifice was built as a traditional Latin colonnaded basilica with galleries and a wooden roof. It was preceded by an atrium. It was claimed to be one of the world's most outstanding monuments at the time.
The Patriarch of Constantinople John Chrysostom came into a conflict with Empress Aelia Eudoxia, wife of the emperor Arcadius, and was sent into exile on 20 June 404. During the subsequent riots, this first church was largely burned down.[16] Nothing remains of the first church today.
Church of Theodosius II
A second church on the site was ordered by Theodosius II, who inaugurated it on 10 October 415. The basilica with a wooden roof was built by architect Rufinus. A fire started during the tumult of the Nika Revolt and burned the second Hagia Sophia to the ground on 13–14 January 532.
Several marble blocks from the second church survive to the present; among them are reliefs depicting 12 lambs representing the 12 apostles. Originally part of a monumental front entrance, they now reside in an excavation pit adjacent to the museum's entrance after they were discovered in 1935 beneath the western courtyard by A. M. Schneider. Further digging was forsaken for fear of impinging on the integrity of the building.

Remains of the second Hagia Sophia

Basilica of the Hagia Sophia (current structure)

On 23 February 532, only a few weeks after the destruction of the second basilica, Emperor Justinian I decided to build a third and entirely different basilica, larger and more majestic than its predecessors.
Justinian chose geometer and engineer Isidore of Miletus and mathematician Anthemius of Tralles as architects; Anthemius, however, died within the first year of the endeavor. The construction is described in the Byzantine historian Procopius' On Buildings (Peri ktismatōn, Latin: De aedificiis). Columns and other marbles were brought from all over the empire, throughout the Mediterranean. The idea of these columns being spoils from cities such as Rome and Ephesus is a later invention.[17] Even though they were made specifically for Hagia Sophia, the columns show variations in size.[18] More than ten thousand people were employed. This new church was contemporaneously recognized as a major work of architecture. The theories of Heron of Alexandria may have been utilized to address the challenges presented by building such an expansive dome over so large a space. The emperor, together with the Patriarch Menas, inaugurated the new basilica on 27 December 537 – 5 years and 10 months after construction start – with much pomp.[19][20][21] The mosaics inside the church were, however, only completed under the reign of Emperor Justin II (565–578).
Hagia Sophia was the seat of the Orthodox patriarch of Constantinople and a principal setting for Byzantine imperial ceremonies, such as coronations. Like other churches throughout Christendom, the basilica offered sanctuary from persecution to outlaws.
Earthquakes in August 553 and on 14 December 557 caused cracks in the main dome and eastern half-dome. The main dome collapsed completely during a subsequent earthquake on 7 May 558,[22] destroying the ambon, altar, and ciborium. The collapse was due mainly to the unfeasibly high bearing load and to the enormous shear load of the dome, which was too flat.[19] These caused the deformation of the piers which sustained the dome.[19] The emperor ordered an immediate restoration. He entrusted it to Isidorus the Younger, nephew of Isidore of Miletus, who used lighter materials and elevated the dome by "30 feet"[19] (about 6.25 meters or 20.5 feet) – giving the building its current interior height of 55.6 meters (182ft).[23] Moreover, Isidorus changed the dome type, erecting a ribbed dome with pendentives, whose diameter lay between 32.7 and 33.5m.[19] Under Justinian's orders, eight Corinthian columns were disassembled from Baalbek, Lebanon, and shipped to Constantinople around 560.[24] This reconstruction, giving the church its present 6th-century form, was completed in 562. The Byzantine poet Paul the Silentiary composed a long epic poem (still extant), known as Ekphrasis, for the rededication of the basilica presided over by Patriarch Eutychius on 23 December 562 A.D.

In 726, the emperor Leo the Isaurian issued a series of edicts against the veneration of images, ordering the army to destroy all icons – ushering in the period of Byzantine iconoclasm. At that time, all religious pictures and statues were removed from the Hagia Sophia. After a brief reprieve under Empress Irene (797–802), the iconoclasts made a comeback. The Emperor Theophilus (829–842) had two-winged bronze doors with his monograms installed at the southern entrance of the church.
The basilica suffered damage, first in a great fire in 859, and again in an earthquake on 8 January 869, that made one of the half-domes collapse. Emperor Basil I ordered the church repaired.
After the great earthquake of 25 October 989, which collapsed the Western dome arch, Emperor Basil II asked for the Armenian architect Trdat, creator of the cathedrals of Ani and Argina, to direct the repairs.[25] He erected again and reinforced the fallen dome arch, and rebuilt the west side of the dome with 15 dome ribs.[26] The extent of the damage required six years of repair and reconstruction; the church was re-opened on 13 May 994. At the end of the reconstruction, the church's decorations were renovated, including the addition of four immense paintings of cherubs; a new depiction of Christ on the dome; a burial cloth of Christ shown on Fridays, and on the apse a new depiction of the Virgin Mary holding Jesus, between the apostles Peter and Paul.[27] On the great side arches were painted the prophets and the teachers of the church.[27]
In his book De caerimoniis aulae Byzantinae ("Book of Ceremonies"), Emperor Constantine VII (913–919) wrote a detailed account of the ceremonies held in the Hagia Sophia by the emperor and the patriarch.
Upon the capture of Constantinople during the Fourth Crusade, the church was ransacked and desecrated by the Crusaders, as described by the Byzantine historian Niketas Choniates. During the Latin occupation of Constantinople (1204–1261) the church became a Roman Catholic cathedral. Baldwin I of Constantinople was crowned emperor on 16 May 1204 in Hagia Sophia, at a ceremony which closely followed Byzantine practices. Enrico Dandolo, the Doge of Venice who commanded the sack and invasion of the city by the Latin Crusaders in 1204, is buried inside the church, probably in the upper Eastern gallery. In the 19th century, an Italian restoration team placed a cenotaph marker near the probable location, which is still visible today. The marker is frequently mistaken by tourists as being a medieval marker of the actual tomb of the doge.  The real tomb was destroyed by the Ottomans after the conquest of Constantinople in 1453 and subsequent conversion of Hagia Sophia into a mosque.[28]
After the recapture in 1261 by the Byzantines, the church was in a dilapidated state. In 1317, emperor Andronicus II ordered four new buttresses (Pyramídas, Greek: "Πυραμίδας") to be built in the eastern and northern parts of the church, financing them with the inheritance of his deceased wife, Irene.[29]  New cracks developed in the dome after the earthquake of October 1344, and several parts of the building collapsed on 19 May 1346; consequently, the church was closed until 1354, when repairs were undertaken by architects Astras and Peralta.
Mosque (1453–1935)
Constantinople fell to the attacking Ottoman forces on the 29th of May in 1453. In accordance with the traditional custom at the time, Sultan Mehmet II allowed his troops and his entourage three full days of unbridled pillage and looting in the city shortly after it was captured. Once the three days passed, he would then claim its remaining contents for himself.[30][31]
Hagia Sophia was not exempted from the pillage and looting and specifically became its focal point as the invaders believed it to contain the greatest treasures and valuables of the city.[32]
Shortly after Constantinople's defenses collapsed and the Ottoman troops entered the city victoriously, the pillagers and looters made their way to the Hagia Sophia and battered down its doors before storming in.[33] All throughout the period of the siege of Constantinople, the trapped worshippers of the city participated in the Divine Liturgy and the Prayer of the Hours at the Hagia Sophia and the church formed a safe-haven and a refuge for many of those who were unable to contribute to the city's defense, which comprised women, children, the elderly and the sick and the wounded.[34][35] Being hopelessly trapped in the church, the many congregants and yet more refugees inside became spoils-of-war to be divided amongst the triumphant invaders. The building was significantly desecrated and looted to a large extent, with the helpless occupants who sought shelter within the church being either enslaved, physically and sexually violated or simply slaughtered.[32] While most of the elderly and the infirm/wounded and sick were killed, a vast number of women and girls were raped and the remainder (mainly teenage males and young boys) were chained up and sold off into slavery.[33] The church's priests and religious personnel continued to perform Christian rites, prayers and ceremonies until finally being forced to stop by the invaders.[33] When Sultan Mehmet II and his accompanying entourage entered the church, he insisted that it should be converted into a mosque at once. One of the ulama (Islamic scholars) present then climbed up the church's pulpit and recited out the Shahada ("There is no God but Allah, and Mohammed is His prophet"), thus marking the beginning of the gradual conversion of the church into a mosque.[29][36]

As described by several Western visitors (such as the Córdoban nobleman Pero Tafur[37] and the Florentine Cristoforo Buondelmonti),[38] the church was in a dilapidated state, with several of its doors fallen from their hinges; Mehmed II ordered a renovation as well as the conversion. Mehmet attended the first Friday prayer in the mosque on 1 June 1453.[39] Aya Sofya became the first imperial mosque of Istanbul.[40] To the corresponding Waqf were endowed most of the existing houses in the city and the area of the future Topkapı Palace.[29]  From 1478, 2,360 shops, 1,300 houses, 4 caravanserais, 30 boza shops, and 23 shops of sheep heads and trotters gave their income to the foundation.[41] Through the imperial charters of 1520 (AH 926) and 1547 (AH 954) shops and parts of the Grand Bazaar and other markets were added to the foundation.[29]
Before 1481 a small minaret was erected on the southwest corner of the building, above the stair tower.[29] Later, the subsequent sultan, Bayezid II (1481–1512), built another minaret at the northeast corner.[29] One of these collapsed after the earthquake of 1509,[29] and around the middle of the 16th century they were both replaced by two diagonally opposite minarets built at the east and west corners of the edifice.[29]

In the 16th century the sultan Suleiman the Magnificent (1520–1566) brought back two colossal candlesticks from his conquest of Hungary. They were placed on either side of the mihrab. During the reign of Selim II (1566–1574), the building started showing signs of fatigue and was extensively strengthened with the addition of structural supports to its exterior by Ottoman architect Mimar Sinan, who was also an earthquake engineer.[42] In addition to strengthening the historic Byzantine structure, Sinan built the two additional large minarets at the western end of the building, the original sultan's lodge and the Türbe (mausoleum) of Selim II to the southeast of the building in 1576–7 / AH 984. In order to do that, parts of the Patriarchate at the south corner of the building were pulled down the previous year.[29] Moreover, the golden crescent was mounted on the top of the dome,[29] while a respect zone 35 arşin (about 24m) wide was imposed around the building, pulling down all the houses which in the meantime had nested around it.[29]  Later his türbe hosted also 43 tombs of Ottoman princes.[29] In 1594 / AH 1004 Mimar (court architect) Davud Ağa built the türbe of Murad III (1574–1595), where the Sultan and his Valide, Safiye Sultan were later buried.[29] The octagonal mausoleum of their son Mehmed III (1595–1603) and his Valide was built next to it in 1608 / AH 1017 by royal architect Dalgiç Mehmet Aĝa.[43] His son Mustafa I (1617–1618; 1622–1623) converted the baptistery into his türbe.[43]
Murad III had also two large alabaster Hellenistic urns transported from Pergamon and placed on two sides of the nave.[29]
In 1717, under Sultan Ahmed III (1703–1730), the crumbling plaster of the interior was renovated, contributing indirectly to the preservation of many mosaics, which otherwise would have been destroyed by mosque workers.[43] In fact, it was usual for them to sell mosaics stones – believed to be talismans – to the visitors.[43] Sultan Mahmud I ordered the restoration of the building in 1739 and added a medrese (a Koranic school, now the library of the museum), an Imaret (soup kitchen for distribution to the poor) and a library, and in 1740 a Şadirvan (fountain for ritual ablutions), thus transforming it into a külliye, i.e. a social complex. At the same time, a new sultan's lodge and a new mihrab were built inside.
Renovation of 1847
Restoration of the Hagia Sophia was ordered by Sultan Abdülmecid and completed by eight hundred workers between 1847 and 1849, under the supervision of the Swiss-Italian architect brothers Gaspare and Giuseppe Fossati. The brothers consolidated the dome and vaults, straightened the columns, and revised the decoration of the exterior and the interior of the building. The mosaics in the upper gallery were exposed and cleaned, although many were recovered "for protection against further damage". The old chandeliers were replaced by new pendant ones. New gigantic circular-framed disks or medallions were hung on columns. These were inscribed with the names of Allah,  Muhammad, the first four caliphs Abu Bakr, Umar, Uthman and Ali, and the two grandchildren of Muhammad: Hassan and Hussain, by the calligrapher Kazasker Mustafa İzzed Effendi (1801–1877). In 1850 the architects Fossati built a new sultan's lodge or loge in a Neo-Byzantine style connected to the royal pavilion behind the mosque. They also renovated the minbar and mihrab. Outside the main building, the minarets were repaired and altered so that they were of equal height.[44][45] A timekeeper's building and a new madrasah (Islamic school) were built.  When the restoration was finished, the mosque was re-opened with ceremonial pomp on 13 July 1849.
Museum (1935–present)

In 1935, the first Turkish President and founder of the Republic of Turkey, Mustafa Kemal Atatürk, transformed the building into a museum. The carpets were removed and marble floor decorations such as the Omphalion appeared for the first time in centuries, while the white plaster covering many of the mosaics was removed. Nevertheless, the condition of the structure deteriorated, and the World Monuments Fund placed Hagia Sophia on 1996 World Monuments Watch, and again in 1998. The building's copper roof had cracked, causing water to leak down over the fragile frescoes and mosaics. Moisture entered from below as well. Rising ground water had raised the level of humidity within the monument, creating an unstable environment for stone and paint. The WMF secured a series of grants from 1997 to 2002 for the restoration of the dome. The first stage of work involved the structural stabilization and repair of the cracked roof, which was undertaken with the participation of the Turkish Ministry of Culture. The second phase, the preservation of the dome's interior, afforded the opportunity to employ and train young Turkish conservators in the care of mosaics. By 2006, the WMF project was complete, though many other areas of Hagia Sophia continue to require significant stability improvement, restoration and conservation.[46] Hagia Sophia is currently (2014) the second most visited museum in Turkey, attracting almost 3.3 million visitors annually.[12]
Although use of the complex as a place of worship (mosque or church) was strictly prohibited,[47]  in 2006 the Turkish government allowed the allocation of a small room in the museum complex to be used as a prayer room for Christian and Muslim museum staff,[48] and since 2013 from the minarets of the museum the muezzin sings the call to prayer twice per day, in the afternoon.[49]
In 2007, Greek American politician Chris Spirou launched an international organization "Free Agia Sophia Council" championing the cause of restoring the building to its original function as a Christian church.[50][51][52] Since the early 2010s, several campaigns and government high officials, notably Turkey's deputy prime minister Bülent Arınç in November 2013, have been demanding that Hagia Sophia be converted into a mosque again.[53][54][55] In 2015, in retaliation for the acknowledgment by Pope Francis of the Armenian Genocide, the Mufti of Ankara, Mefail Hızlı, stated that he believes the conversion of Hagia Sophia into a mosque will be accelerated.[56][57]
On July 1, 2016, Muslim prayers were held again in the Hagia Sophia for the first time in 85 years.[58]
On May 13, 2017, a large group of people organized by the Anatolia Youth Association (AGD), gathered in front of Hagia Sophia and prayed the morning prayer with a call for the reconversion of the museum into a mosque.[59] On June 21, 2017, Presidency of Religious Affairs (Diyanet) organized a special program, which included the recitation of the Quran and prayers in Hagia Sofia, to mark the Laylat al-Qadr, the program was broadcast live by state-run television TRT.[60]
In March 31, 2018, Turkish president Recep Tayyip Erdoğan recited the first verse of the Quran in the Hagia Sophia, dedicating the prayer to the "souls of all who left us this work as inheritance, especially Istanbul's conqueror," strengthening the political movement to make the Hagia Sophia a mosque once again, which would reverse Atatürk's measure of turning the Hagia Sophia into a secular museum.[61]
Timeline of Hagia Sophia
360 A.D – Inauguration of Hagia Sophia, under the rule of Constantius II.
404 A.D – The original roof was destroyed in a fire.
415 A.D – Hagia Sophia was restored and rededicated by Theodosius II.
532 A.D – Hagia Sophia was burned down once again. The structure was completely destroyed alongside various other churches. After a mere 93 days, construction of the Hagia Sophia began.
537 A.D – The reconstruction was completed with the lavish decorations and ornaments
553 A.D – An earthquake shook Hagia Sophia, weakening the crown of Eastern arch.
558 A.D – Another earthquake hit, causing a break between the two halves. A few months after, the main dome collapsed alongside the eastern semidome. This caused the destruction of the ambo, ciborium, and the Holy Table.
562 A.D – Reconstruction was completed.
726 A.D – Hagia Sophia was stripped of religious illustrations and sculptural work.
842 A.D – St Sophia was finally re-installed. Commencing the redecoration of Hagia Sophia.
859 A.D – A great fire damaged the Hagia Sophia.
869 A.D – An earthquake caused a half dome to collapse.
989 A.D – Another massive earthquake caused the collapse of the western dome.
994 A.D – Hagia Sophia was reopened after reconstruction took place.
1204 A.D – Hagia Sophia became a Roman Catholic Cathedral.
1261 A.D – Hagia Sophia was converted to an Orthodox Church again.
1344 A.D – An earthquake caused severe damage throughout the striation
1346 A.D – Various parts of the building collapsed and the church was closed.
1354 A.D – Hagia Sophia reopened after construction.
1453 A.D – Following the fall of Constantinople, Mehmed the Conqueror orders the conversion of Hagia Sophia into a mosque. Τhe Divine Service in Hagia Sophia at the time of the Salvation was interrupted.
1573 A.D – The exterior was significantly strengthened and altered to follow the customary mosque appearance.
1717 A.D – Renovations on the interior began.
1734 A.D – Hagia Sophia had additions to restorations, such as the building of a library and a Quranic School.
1847 A.D – The structure underwent another restoration
1849 A.D – the mosque was reopened.
1919 A.D. Τhe Divine Service in Hagia Sophia, which had interrupted after the Salvation in 1453 A.D., was continued and completed by a Greek military priest.[62]
1935 A.D – the building was transformed into a museum.
[63]
Architecture

Hagia Sophia is one of the greatest surviving examples of Byzantine architecture.[1] Its interior is decorated with mosaics and marble pillars and coverings of great artistic value. The temple itself was so richly and artistically decorated that Justinian proclaimed, "Solomon, I have outdone thee!" (Νενίκηκά σε Σολομών). Justinian himself had overseen the completion of the greatest cathedral ever built up to that time, and it was to remain the largest cathedral for 1,000 years up until the completion of the cathedral in Seville in Spain.[64]
Justinian's basilica was at once the culminating architectural achievement of late antiquity and the first masterpiece of Byzantine architecture. Its influence, both architecturally and liturgically, was widespread and enduring in the Eastern Orthodox, Roman Catholic, and Muslim worlds alike.
The vast interior has a complex structure. The nave is covered by a central dome which at its maximum is 55.6m (182ft 5in) from floor level and rests on an arcade of 40 arched windows. Repairs to its structure have left the dome somewhat elliptical, with the diameter varying between 31.24 and 30.86m (102ft 6in and 101ft 3in).
At the western entrance side and eastern liturgical side, there are arched openings extended by half domes of identical diameter to the central dome, carried on smaller semi-domed exedras; a hierarchy of dome-headed elements built up to create a vast oblong interior crowned by the central dome, with a clear span of 76.2m (250ft).[1]
Interior surfaces are sheathed with polychrome marbles, green and white with purple porphyry, and gold mosaics. The exterior, clad in stucco, was tinted yellow and red during restorations in the 19th century at the direction of the Fossati architects.
Narthex and portals
The Imperial Gate was the main entrance between the exo- and esonarthex. It was reserved exclusively for the Emperor. The Byzantine mosaic above the portal depicts Christ and an unnamed emperor. A long ramp from the northern part of the outer narthex leads up to the upper gallery.
Upper gallery
Throughout history the Hagia Sophia has been a victim to natural disasters, such as earthquakes, and has also fallen victim to vandalism. Structural damage can easily be seen on its exterior surface. To ensure that the Hagia Sophia did not ensue any damage on the interior of the building, studies have been conducted using ground penetrating radar within the gallery of the Hagia Sophia. With the use of GPR (ground penetrating radar), teams discovered weak zones within the Hagia Sophia's gallery and also concluded that the curvature of the vault dome has been shifted out of proportion, compared to its original angular orientation.[65]
The upper gallery is laid out in a horseshoe shape that encloses the nave until the apse. Several mosaics are preserved in the upper gallery, an area traditionally reserved for the Empress and her court. The best-preserved mosaics are located in the southern part of the gallery.
The upper gallery contains runic graffiti presumed to be from the Varangian Guard.
Dome

The dome of Hagia Sophia has spurred particular interest for many art historians, architects and engineers because of the innovative way the original architects envisioned it. The dome is carried on four spherical triangular pendentives, one of the first large-scale uses of them. The pendentives are the corners of the square base of the dome, which curve upwards into the dome to support it, restraining the lateral forces of the dome and allowing its weight to flow downwards.[66][67] It was the largest pendentive dome in the world until the completion of St. Peter's Basilica, and has a much lower height than any other dome of such a large diameter.
The great dome at the Hagia Sophia is one hundred and seven feet in diameter and is only two feet thick. The main building material for the Hagia Sophia composed of brick and mortar. Brick aggregate was used to make roofs easier to construct. The aggregate weighs one hundred and fifty pounds per cubic foot, an average weight of masonry construction at the time. Due to the materials plasticity it was chosen over cut stone due to the fact that aggregate can be used over a longer distance.[68]
The weight of the dome remained a problem for most of the building's existence. The original cupola collapsed entirely after the earthquake of 558; in 563 a new dome was built by Isidore the younger, a nephew of Isidore of Miletus. Unlike the original, this included 40 ribs and was raised 20 feet, in order to lower the lateral forces on the church walls. A larger section of the second dome collapsed as well, in two episodes, so that today only two sections of the present dome, in the north and south side, still date from the 562 reconstructions. Of the whole dome's 40 ribs, the surviving north section contains eight ribs, while the south section includes six ribs.[69]
Although this design stabilizes the dome and the surrounding walls and arches, the actual construction of the walls of Hagia Sophia weakened the overall structure. The bricklayers used more mortar than brick, which is more effective if the mortar was allowed to settle as the building would have been more flexible; however, the builders raced to complete the building and left no time for the mortar to cure before they began the next layer. When the dome was erected, its weight caused the walls to lean outward because of the wet mortar underneath. When Isidore the Younger rebuilt the fallen cupola, he had first to build up the interior of the walls to make them vertical again. Additionally, the architect raised the height of the rebuilt dome by approximately sixm (20 feet) so that the lateral forces would not be as strong and its weight would be transmitted more effectively down into the walls. Moreover, he shaped the new cupola like a scalloped shell or the inside of an umbrella, with ribs that extend from the top down to the base. These ribs allow the weight of the dome to flow between the windows, down the pendentives, and ultimately to the foundation.[70]
Hagia Sophia is famous for the light that reflects everywhere in the interior of the nave, giving the dome the appearance of hovering above. This effect was achieved by inserting forty windows around the base of the original structure. Moreover, the insertion of the windows in the dome structure lowers its weight.[70]
Minarets
The minarets were an Ottoman addition and not part of the original church's Byzantine design. They were built for notification of invitations for prayers and announcements. Mehmed had built a minaret made from wood over one of the half domes soon after Hagia Sophia's conversion from a cathedral to a mosque. This minaret does not exist today. One of the minarets (at southwest) was built from red brick and can be dated back from the Fatih Sultan Mehmed period or Beyazıd II period. The other three were built from white limestone and sandstone, of which the slender northeast column was erected by Sultan Bayezid II during the Selim II period, while the two identical larger minarets to the west were erected by Sultan Selim II and designed by the famous Ottoman architect Mimar Sinan. Both are 60 metres in height, and with their thick and massif patterns, complete Hagia Sophia's main structure. Many ornaments and details were added to these minarets on repairs during the 15th, 16th, and 19th centuries, which reflect each period's characteristics and ideals.[71][72]
Buttresses
Numerous buttresses have been added throughout the centuries. The flying buttresses to the west of the building, although thought to have been constructed by the Crusaders upon their visit to Constantinople, are actually built during the Byzantine era. This shows that the Byzantines had prior knowledge of flying buttresses which can also be seen at Hosios Loukas in Central Greece, the Rotunda of Galerius in Thessaloniki, and San Vitale in Ravenna.[70] Other buttresses were constructed during the Ottoman times under the guidance of the architect Sinan. A total of 24 buttresses were added.[73]
Notable elements and decorations
Originally, under Justinian's reign, the interior decorations consisted of abstract designs on marble slabs on the walls and floors, as well as mosaics on the curving vaults. Of these mosaics, one can still see the two archangels Gabriel and Michael in the spandrels of the bema. There were already a few figurative decorations, as attested by the eulogy of Paul the Silentiary. The spandrels (corners) of the gallery are faced in inlaid thin slabs (opus sectile), showing patterns and figures of flowers and birds in precisely cut pieces of white marble set against a background of black marble. In later stages, figurative mosaics were added, which were destroyed during the iconoclastic controversy (726–843). Present mosaics are from the post-iconoclastic period.
Apart from the mosaics, a large number of figurative decorations were added during the second half of the 9th century: an image of Christ in the central dome; Orthodox saints, prophets and Church Fathers in the tympana below; historical figures connected with this church, such as Patriarch Ignatius; some scenes from the gospel in the galleries.
Basil II let artists paint on each of the four pendentives a giant six-winged Cherub.[27] The Ottomans covered their face with a golden halo,[27] but in 2009 one of them was restored to the original state.[74]

The Loge of the Empress. The columns are made of green Thessalian stone
Lustration urn from Pergamon
Marble Door
The wishing column

Loggia of the Empress
The Loggia of the Empress is located in the centre of the upper enclosure, or gallery, of the Hagia Sophia. From there the empress and the court-ladies would watch the proceedings down below. A round green stone marks the spot where the throne of the empress stood.[75][76]
Lustration urns
Two huge marble lustration (ritual purification)  urns were brought from Pergamon during the reign of Sultan Murad III. From the Hellenistic period, they are carved from single blocks of marble.[29]
Marble Door
The Marble Door inside the Hagia Sophia is located in the southern upper enclosure or gallery. It was used by the participants in synods, who entered and left the meeting chamber through this door. It is said that each side is symbolic and that one side represents heaven while the other represents hell. Its panels are covered in fruits and fish motives. The door opens into a space that was used as a venue for solemn meetings and important resolutions of patriarchate officials.[77]
The Nice Door
The Nice Door is the oldest architectural element found in the Hagia Sophia dating back to the 2nd century BC. The decorations are of reliefs of geometric shapes as well as plants that are believed to have come from a pagan temple in Tarsus, Mersin now modern-day Turkey. It was incorporated into the building by Emperor Theophilos in 838AD where it is placed in the south exit in the inner narthex.[78]
The Emperor Door
The Emperor Door is the door that would be used solely by the Emperor as well as his personal bodyguard and retinue. It is the largest door in the Hagia Sophia and has been dated to the 6th century. It is about 7 meters long and Eastern Roman sources say it was made with wood from Noah's Ark.[79]
Wishing column
At the northwest of the building, there is a column with a hole in the middle covered by bronze plates. This column goes by different names; the perspiring column, the wishing column, the sweating column or the crying column. The column is said to be damp when touched and have supernatural powers.[80] The legend states that since St. Gregory the Miracle Worker appeared near the column in the year 1200, it has been moist. It is believed that touching the moisture cures many illnesses.[81][82]
Mosaics

The first mosaics which adorned the church were only completed during the reign of Justin II.[83] Many of the non-figurative mosaics in the church come from this period. Most of the mosaics, however, were completed after the end of the periods of Byzantine Iconoclasm in 843 AD.
During the Sack of Constantinople in 1204, the Latin Crusaders vandalized valuable items in every important Byzantine structure of the city, including the golden mosaics of the Hagia Sophia. Many of these items were shipped to Venice, whose Doge, Enrico Dandolo, had organized the invasion and sack of Constantinople after an agreement with Prince Alexios Angelos, the son of a deposed Byzantine emperor.
19th-century restoration
Following the building's conversion into a mosque in 1453, many of its mosaics were covered with plaster, due to Islam's ban on representational imagery. This process was not completed at once, and reports exist from the 17th century in which travelers note that they could still see Christian images in the former church. In 1847–49, the building was restored by two Swiss-Italian Fossati brothers, Gaspare and Giuseppe, and Sultan Abdülmecid allowed them to also document any mosaics they might discover during this process which were later archived in Swiss libraries.[84] This work did not include repairing the mosaics and after recording the details about an image, the Fossatis painted it over again. The Fossatis restored the mosaics of the two hexapteryga (singular Greek: ἑεξαπτέρυγον, pr. hexapterygon, six-winged angel; it is uncertain whether they are seraphim or cherubim) located on the two east pendentives, covering their faces again before the end of the restoration.[85] The other two placed on the west pendentives are copies in paint created by the Fossatis since they could find no surviving remains of them.[85] As in this case, the architects reproduced in paint damaged decorative mosaic patterns, sometimes redesigning them in the process. The Fossati records are the primary sources about a number of mosaic images now believed to have been completely or partially destroyed in the 1894 Istanbul earthquake. These include a mosaic over a now-unidentified Door of the Poor, a large image of a jewel-encrusted cross, and a large number of images of angels, saints, patriarchs, and church fathers. Most of the missing images were located in the building's two tympana.
One mosaic they documented is Christ Pantocrator in a circle, which would indicate it to be a ceiling mosaic, possibly even of the main dome which was later covered and painted over with Islamic calligraphy that expounds God as the light of the universe. The drawings of the Hagia Sophia mosaics are today kept in the Cantonal Archive of Ticino.[86]
20th-century restoration
A large number of mosaics were uncovered in the 1930s by a team from the Byzantine Institute of America led by Thomas Whittemore. The team chose to let a number of simple cross images remain covered by plaster but uncovered all major mosaics found.
In 2000, The National Technical University of Athens has begun to use Non Destructive Techniques along with infrared technology to scan walls of the Hagia Sophia to locate mosaics that have been previously covered with plaster. The National Technical University of Athens is using infrared technology, to assess the damage mosaics have taken within the Hagia Sophia beneath the plaster. The National Technical University of Athens uses categories such as water intrusion to determine a mosaics current state of condition.[87]
Because of its long history as both a church and a mosque, a particular challenge arises in the restoration process. Christian iconographic mosaics can be uncovered, but often at the expense of important and historic Islamic art. Restorers have attempted to maintain a balance between both Christian and Islamic cultures. In particular, much controversy rests upon whether the Islamic calligraphy on the dome of the cathedral should be removed, in order to permit the underlying Pantocrator mosaic of Christ as Master of the World, to be exhibited (assuming the mosaic still exists).[88]
The Hagia Sophia has been a victim to natural disasters that have caused deterioration to the buildings structure and walls. The deterioration of the Hagia Sophia's walls can be directly relate to salt crystallization. The crystallization of salt is due to an intrusion of rainwater that is at fault for the Hagia Sophia's deteriorating inner and outer walls. Diverting excess rainwater is the main solution to solve the deteriorating walls at the Hagia Sophia.[89]
Built between 532-537 a subsurface structure under the Hagia Sophia has been under investigation, using LaCoste-Romberg gravimeters to determine the depth of the subsurface structure and to discover other hidden cavities beneath the Hagia Sophia.The hidden cavities have also acted as a support system against earthquakes. With these findings using the LaCoste-Romberg gravimeters, it was also discovered that the Hagia Sophia's foundation is built on a slope of natural rock.[90]
Imperial Gate mosaic

The Imperial Gate mosaic is located in the tympanum above that gate, which was used only by the emperors when entering the church. Based on style analysis, it has been dated to the late 9th or early 10th century. The emperor with a nimbus or halo could possibly represent emperor Leo VI the Wise or his son Constantine VII Porphyrogenitus bowing down before Christ Pantocrator, seated on a jeweled throne, giving His blessing and holding in His left hand an open book.[91] The text on the book reads as follows: "Peace be with you. I am the light of the world". (John 20:19; 20:26; 8:12) On each side of Christ's shoulders is a circular medallion: on His left the Archangel Gabriel, holding a staff, on His right His Mother Mary.[92]
Southwestern entrance mosaic

The southwestern entrance mosaic, situated in the tympanum of the southwestern entrance, dates from the reign of Basil II.[93] It was rediscovered during the restorations of 1849 by the Fossatis. The Virgin sits on a throne without a back, her feet resting on a pedestal, embellished with precious stones. The Child Christ sits on her lap, giving His blessing and holding a scroll in His left hand. On her left side stands emperor Constantine in ceremonial attire, presenting a model of the city to Mary. The inscription next to him says: "Great emperor Constantine of the Saints". On her right side stands emperor Justinian I, offering a model of the Hagia Sophia. The medallions on both sides of the Virgin's head carry the monograms MP and ΘΥ, an abbreviation of "Mētēr" and "Theou", meaning "Mother of God".[94]

Apse mosaics

The Virgin and Child mosaic was the first of the post-iconoclastic mosaics. It was inaugurated on 29 March 867 by Patriarch Photius and the emperors Michael III and Basil I. This mosaic is situated in a high location on the half dome of the apse. Mary is sitting on a throne without a back, holding the Child Jesus on her lap. Her feet rest on a pedestal. Both the pedestal and the throne are adorned with precious stones. The portraits of the archangels Gabriel and Michael (largely destroyed) in the bema of the arch also date from the 9th century. The mosaics are set against the original golden background of the 6th century. These mosaics were believed to be a reconstruction of the mosaics of the 6th century that were previously destroyed during the iconoclastic era by the Byzantines of that time, as represented in the inaugural sermon by the patriarch Photios. However, no record of figurative decoration of Hagia Sophia exists before this time.[95]
Emperor Alexander mosaic
The Emperor Alexander mosaic is not easy to find for the first-time visitor, located on the second floor in a dark corner of the ceiling. It depicts Emperor Alexander in full regalia, holding a scroll in his right hand and a globus cruciger in his left. A drawing by the Fossatis showed that the mosaic survived until 1849 and that Thomas Whittemore, founder of the Byzantine Institute of America who was granted permission to preserve the mosaics, assumed that it had been destroyed in the earthquake of 1894. Eight years after his death, the mosaic was discovered in 1958 largely through the researches of Robert Van Nice. Unlike most of the other mosaics in Hagia Sophia, which had been covered over by ordinary plaster, the Alexander mosaic was simply painted over and reflected the surrounding mosaic patterns and thus was well hidden. It was duly cleaned by the Byzantine Institute's successor to Whittemore, Paul A. Underwood.[96][97]
Empress Zoe mosaic

The Empress Zoe mosaic on the eastern wall of the southern gallery date from the 11th century. Christ Pantocrator, clad in the dark blue robe (as is the custom in Byzantine art), is seated in the middle against a golden background, giving His blessing with the right hand and holding the Bible in His left hand. On either side of His head are the monograms IC and XC, meaning Iēsous Christos. He is flanked by Constantine IX Monomachus and Empress Zoe, both in ceremonial costumes. He is offering a purse, as a symbol of donation, he made to the church, while she is holding a scroll, symbol of the donations she made. The inscription over the head of the emperor says: "Constantine, pious emperor in Christ the God, king of the Romans, Monomachus". The inscription over the head of the empress reads as follows: "Zoë, the very pious Augusta". The previous heads have been scraped off and replaced by the three present ones. Perhaps the earlier mosaic showed her first husband Romanus III Argyrus or her second husband Michael IV. Another theory is that this mosaic was made for an earlier emperor and empress, with their heads changed into the present ones.[98]
Comnenus mosaic

The Comnenus mosaic, also located on the eastern wall of the southern gallery, dates from 1122. The Virgin Mary is standing in the middle, depicted, as usual in Byzantine art, in a dark blue gown. She holds the Child Christ on her lap. He gives His blessing with His right hand while holding a scroll in His left hand. On her right side stands emperor John II Comnenus, represented in a garb embellished with precious stones. He holds a purse, symbol of an imperial donation to the church. Empress Irene stands on the left side of the Virgin, wearing ceremonial garments and offering a document. Their eldest son Alexius Comnenus is represented on an adjacent pilaster. He is shown as a beardless youth, probably representing his appearance at his coronation aged seventeen. In this panel, one can already see a difference with the Empress Zoe mosaic that is one century older. There is a more realistic expression in the portraits instead of an idealized representation. The Empress, Saint Irene (born Piroska), daughter of Ladislaus I of Hungary is shown with plaited blond hair, rosy cheeks, and grey eyes, revealing her Hungarian descent. The emperor is depicted in a dignified manner.[99]
Deësis mosaic

The Deësis mosaic (Δέησις, "Entreaty") probably dates from 1261. It was commissioned to mark the end of 57 years of Roman Catholic use and the return to the Orthodox faith. It is the third panel situated in the imperial enclosure of the upper galleries. It is widely considered the finest in Hagia Sophia, because of the softness of the features, the humane expressions and the tones of the mosaic. The style is close to that of the Italian painters of the late 13th or early 14th century, such as Duccio. In this panel the Virgin Mary and John the Baptist (Ioannes Prodromos), both shown in three-quarters profile, are imploring the intercession of Christ Pantocrator for humanity on Judgment Day. The bottom part of this mosaic is badly deteriorated.[100] This mosaic is considered as the beginning of the Renaissance in Byzantine pictorial art.[101]
Northern tympanum mosaics
The northern tympanum mosaics feature various saints. They have been able to survive due to the very high and unreachable location. They depict Saints John Chrysostom and Ignatius the Younger standing, clothed in white robes with crosses, and holding richly jeweled Holy Bibles. The names of each saint are given around the figures in Greek, in order to enable an identification for the visitor. The other mosaics in the other tympana have not survived probably due to the frequent earthquakes as opposed to any deliberate destruction by the Ottoman conquerors.[102]
Dome Angel Figure Mosaic
This features four unidentical angel figures. It is believed that these on headed six winged angels, also known as seraphim, protect the lords throne in heaven. There are angels in the east composed in mosaics as where the ones in the west were damaged during the Eastern Roman Period, they have been renewed as fresco. During the ottoman period the angels faces were covered with metallic lids in the shape of stars, but were removed to reveal the faces in 2009 during renovations.[103]
Other burials
Mustafa I, in the courtyard
Enrico Dandolo, in the east gallery
Gallery

Mosaics with geometric pattern decorate the upper imperial gallery
Detail of Deësis mosaic
Mosaic in the northern tympanum depicting Saint John Chrysostom
Drawing by the Fossati brother depicting some mosaics
Another drawing by the Fossati brothers depicting mosaic of six patriarchs in the southern tympanum
One of the mighty stone columns with metal clasps
Interior of the Hagia Sophia by John Singer Sargent, 1891
Detail of relief on the Marble Door.
Interior view of the Hagia Sophia, showing Islamic elements on the top of the main dome ().
Haghia Sofia from Adriaan Reland (1676–1718): Verhandeling van de godsdienst der Mahometaanen, 1719
Hagia Sophia during its time as a mosque. Illustration by Gaspare Fossati and Louis Haghe from 1852.
Interior panorama of the Hagia Sophia ().
Circa 1900 photograph, from its time as a mosque.
The face of the Hexapterygon (six-winged angel) on the northeast pendentive (upper left), discovered but covered again by Gaspare Fossati during its restoration, is visible again ().
Imperial Gate
19th-century marker of the tomb of Enrico Dandolo, the Doge of Venice who commanded the Sack of Constantinople in 1204, inside the Hagia Sophia

Works modeled on the Hagia Sofia
Many religious structures have been modeled on the Hagia Sophia's core structure of a large central dome resting on pendentives and buttressed by two semi-domes. A notable Venetian example is the High Altar of Santa Maria della Salute.
Several mosques commissioned by the Ottoman dynasty closely mimic the geometry of the Hagia Sophia, including the Süleymaniye Mosque and the Bayezid II Mosque. In many cases, Ottoman architects preferred to surround the central dome with four semi-domes rather than two. This is true in the Sultan Ahmed Mosque, the New Mosque (Istanbul), and the Fatih Mosque. Like the original plan of the Hagia Sophia, many of these mosques are also entered through a colonnaded courtyard. However, the courtyard of the Hagia Sophia no longer exists.
Many Neo-Byzantine churches are modeled on the Hagia Sophia. The Kronstadt Naval Cathedral and Poti Cathedral closely replicate the internal geometry of the Hagia Sophia. The interior of the Kronstadt Naval Cathedral is a nearly 1-to-1 copy of the Hagia Sophia. The marble revetment also closely mimics the source work.  Like Ottoman mosques, many churches based on the Hagia Sophia include four semi-domes rather than two, such as the Church of Saint Sava in Belgrade.
Several churches combine the layout of the Hagia Sophia with a Latin cross plan. For instance, the Cathedral Basilica of Saint Louis (St. Louis), where the transept is formed by two semi-domes surrounding the main dome. This church also closely emulates the column capitals and mosaic styles of the Hagia Sophia. Other similar examples include the Alexander Nevsky Cathedral, Sofia, Saint Clement Catholic Church, Chicago, and Basilica of the National Shrine of the Immaculate Conception.
The Catedral Metropolitana Ortodoxa in São Paulo and the Église du Saint-Esprit (Paris) closely follow the interior layout of the Hagia Sophia. Both include four semi-domes, but the two lateral semi-domes are very shallow. In terms of size, the Église du Saint-Esprit is about two thirds the scale of the Hagia Sophia.
Synagogues based on the Hagia Sophia include the Congregation Emanu-El (San Francisco), Great Synagogue of Florence, and Hurva Synagogue.
See also

Oldest churches in the world
List of megalithic sites
Conversion of non-Muslim places of worship into mosques
Pendentive—Architectural element
List of Byzantine inventions
Islam in Turkey
Ottoman architecture
List of mosques in Istanbul
List of mosques in Turkey
List of mosques
Sultan Ahmed Mosque
History of Roman and Byzantine domes
Related Buildings:
Church of the Holy Apostles—the second most important church of Constantinople
Hagia Irene—neighbouring church
Little Hagia Sophia—a 6th-century Byzantine church, now mosque, that might have been built by the same architects as Hagia Sophia
Church of St. Polyeuctus – An earlier church that may have served as a model for the Hagia Sophia
Chora Church — Byzantine church in Istanbul notable for its well preserved Paleologan mosaics, now a museum too
Pammakaristos Church: its parekklesion—also a museum—is decorated with beautiful mosaics
Haseki Hürrem Sultan Hamamı—bath commissioned by Roxelana for the Hagia Sophia community
Caferağa Medresseh—former Koranic school next to Hagia Sophia
Soğukçeşme Sokağı—historical street between the Hagia Sophia and Topkapı Palace
Saint Sophia Cathedral in Kiev
Saint Sophia Cathedral in Novgorod
Saint Sophia Cathedral in Polotsk
Hagia Sophia Church (Sofia)

Bibliography

 , also known as Church of Holy Wisdom.
Hagia Sophia. . Accessed 23 Sept 2014.

.

Runciman, Steven (1965). , 1453. Cambridge: Cambridge University Press. p.145. ISBN0-521-39832-0.

Further reading

Harris, Jonathan, Constantinople: Capital of Byzantium. Hambledon/Continuum (2007). ISBN978-1-84725-179-4

Scharf, Joachim:Der Kaiser in Proskynese. Bemerkungen zur Deutung des Kaisermosaiks im Narthex der Hagia Sophia von Konstantinopel. In: Festschrift Percy Ernst Schramm zu seinem siebzigsten Geburtstag von Schülern und Freunden zugeeignet, Wiesbaden 1964, S. 27–35.

Weitzmann, Kurt, ed., , no. 592, 1979, Metropolitan Museum of Art, New York, ISBN978-0-87099-179-0
Articles
Bordewich, Fergus M., , Smithsonian magazine, December 2008
Mosaics
Hagia Sophia, .

 by Procopius, Buildings (De Aedificiis), published in 561.