125-646: The Horsethief Sandstone is a Mesozoic geologic formation in Montana . Dinosaur remains are among the fossils that have been recovered from the formation, although none have yet been referred to a specific genus . The southern part of the Two Medicine Formation grades into the brackish water siltstone/sandstone series that compose the Horsethief Formation. To the north the Horsethief Sandstone
250-574: A Stonesfield Slate mine during the early 1790s and was acquired in October 1797 by Christopher Pegge for 10s.6d. and added to the collection of the Anatomy School of Christ Church, Oxford . In the early nineteenth century, more discoveries were made. In 1815, John Kidd reported the find of bones of giant tetrapods, again at the Stonesfield quarry. The layers there are currently considered part of
375-519: A conserved name to ensure its priority. However, the Executive Secretary of the ICZN at the time, Philip K. Tubbs, did not consider the petition to be admissible, concluding that the term "Scrotum humanum", published merely as a label for an illustration, did not constitute the valid creation of a new name, and stated that there was no evidence it was ever intended as such. Furthermore, the partial femur
500-463: A fish tooth (called Plectronites ), later believed to be part of a belemnite , that was illustrated alongside the holotype tooth of the sauropod " Rutellum impicatum" and another tooth, from a theropod , in 1699. Later studies found that the theropod tooth, known as specimen 1328 ( University of Oxford coll. #1328; lost?) almost certainly was a tooth crown that belonged to an unknown species of Megalosaurus . OU 1328 has since been lost and it
625-471: A hyposphene – hypantrum complex, the hyposphene having a triangular transverse cross-section. The height of the dorsal spines of the rear dorsals is unknown, but a high spine on a tail vertebra of the New Park Quarry material, specimen NHMUK PV R9677, suggests the presence of a crest on the hip area. The spines of the five vertebrae of the sacrum form a supraneural plate, fused at the top. The undersides of
750-402: A "wastebasket taxon", and many large or small carnivorous dinosaurs from Europe and elsewhere were assigned to the genus. This slowly changed during the 20th century, when it became common to restrict the genus to fossils found in the middle Jurassic of England. Further restriction occurred in the late 20th and early 21st centuries, researchers such as Ronan Allain and Dan Chure suggesting that
875-476: A boom of dinosaurian evolution on land as the continents began to separate from each other (Nyasasaurus from 243 to 210 million years ago, approximately 235–30 ma, some of them separated into Sauropodomorphs, Theropods and Herrerasaurids), as well as the first pterosaurs . During the Late Triassic, some advanced cynodonts gave rise to the first Mammaliaformes . All this climatic change, however, resulted in
1000-582: A coating. This contrasts with the earth's current flora, in which the dominant land plants in terms of number of species are angiosperms . The earliest members of the genus Ginkgo first appeared during the Middle Jurassic. This genus is represented today by a single species, Ginkgo biloba . Modern conifer groups began to radiate during the Jurassic. Bennettitales , an extinct group of gymnosperms with foliage superficially resembling that of cycads gained
1125-401: A crown length up to seven centimetres. The teeth are supported from behind by tall, triangular, unfused interdental plates. The cutting edges bear 18 to 20 denticula per centimetre. The tooth formula is probably 4, 13–14/13–14. The jugal bone is pneumatised, pierced by a large foramen from the direction of the antorbital fenestra. It was probably hollowed out by an outgrowth of an air sac in
1250-584: A decline in diversity of sauropods, stegosaurs, and other high-browsing groups, with sauropods particularly scarce in North America. Some island-hopping dinosaurs, such as Eustreptospondylus , evolved to cope with the coastal shallows and small islands of ancient Europe. Other dinosaurs rose up to fill the empty space that the Jurassic-Cretaceous extinction left behind, such as Carcharodontosaurus and Spinosaurus . Seasons came back into effect and
1375-477: A few million years before the Triassic–Jurassic extinction event. Sea levels began to rise during the Jurassic, probably caused by an increase in seafloor spreading . The formation of new crust beneath the surface displaced ocean waters by as much as 200 m (656 ft) above today's sea level, flooding coastal areas. Furthermore, Pangaea began to rift into smaller divisions, creating new shoreline around
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#17328510304171500-477: A global distribution during the Late Triassic, and represented one of the most common groups of Mesozoic seed plants. Flowering plants radiated during the early Cretaceous, first in the tropics , but the even temperature gradient allowed them to spread toward the poles throughout the period. By the end of the Cretaceous, angiosperms dominated tree floras in many areas, although some evidence suggests that biomass
1625-659: A large die-out known as the Triassic–Jurassic extinction event, in which many archosaurs (excluding pterosaurs, dinosaurs and crocodylomorphs ), most synapsids , and almost all large amphibians became extinct, as well as 34% of marine life, in the Earth's fourth mass extinction event. The cause is debatable; flood basalt eruptions at the Central Atlantic magmatic province is cited as one possible cause. The Jurassic ranges from 200 million years to 145 million years ago and features three major epochs: The Early Jurassic,
1750-480: A length of 232 millimetres and a minimal shaft circumference of 142 millimetres. The ulna is straight in front view and has a large olecranon , the attachment process for the Musculus triceps brachii . Radius , wrist and hand are unknown. In the pelvis, the ilium is long and low, with a convex upper profile. Its front blade is triangular and rather short; at the front end there is a small drooping point, separated by
1875-441: A length of about 86 centimetres. In general, Megalosaurus had the typical build of a large theropod. It was bipedal, the horizontal torso being balanced by a long horizontal tail. The hindlimbs were long and strong with three forward-facing weight-bearing toes, the forelimbs relatively short but exceptionally robust and probably carrying three digits. Being a carnivore , its large elongated head bore long dagger-like teeth to slice
2000-480: A limestone quarry at Ardley , 20 kilometres northeast of Oxford . They were thought to have been made by Megalosaurus and possibly also some left by Cetiosaurus . There are replicas of some of these footprints, set across the lawn of the Oxford University Museum of Natural History . One track was of a theropod accelerating from walking to running. According to Benson, such referrals are unprovable, as
2125-657: A mammal-like quadruped. The sculpture in Crystal Palace Park shows a conspicuous hump on the shoulders and it has been suggested this was inspired by a set of high vertebral spines acquired by Owen in the early 1850s. Today, they are seen as a separate genus Becklespinax , but Owen referred them to Megalosaurus . The models at the exhibition created a general public awareness for the first time, at least in England, that ancient reptiles had existed. The presumption that carnivorous dinosaurs, like Megalosaurus , were quadrupeds
2250-505: A massive bone plate. On the front outer side of the shaft a large triangular deltopectoral crest is present, the attachment for the Musculus pectoralis major and the Musculus deltoideus . It covers about the upper half of the shaft length, its apex positioned rather low. The ulna is extremely robust, for its absolute size more heavily built than with any other known member of the Tetanurae. The only known specimen, NHMUK PV OR 36585, has
2375-476: A more accurate picture, by comparing Megalosaurus with its direct relatives in the Megalosauridae . Megalosaurus was about 6 metres (20 ft) long, weighing about 700 kilograms (1,500 lb). It was bipedal, walking on stout hindlimbs, its horizontal torso balanced by a horizontal tail. Its forelimbs were short, though very robust. Megalosaurus had a rather large head, equipped with long curved teeth. It
2500-409: A more flexible joint, allowing for a modicum of horizontal movement. The top inner side of the third metatarsal carries a unique ridge that fits into a groove along the top outer side of the second metatarsal, causing a tighter connection. For decades after its discovery, Megalosaurus was seen by researchers as the definitive or typical large carnivorous dinosaur. As a result, it began to function as
2625-402: A notch from the pubic peduncle. The rear blade is roughly rectangular. The outer side of the ilium is concave, serving as an attachment surface for the Musculus iliofemoralis , the main thigh muscle. Above the hip joint, on this surface a low vertical ridge is present with conspicuous vertical grooves. The bottom of the rear blade is excavated by a narrow but deep trough forming a bony shelf for
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#17328510304172750-430: A piece of the pubic bone ; OUM J13565, a part of the ischium ; OUM J13561, a thigh bone and OUM J13572, the lower part of a second metatarsal . As he himself was aware, these did not all belong to the same individual; only the sacrum was articulated. Because they represented several individuals, the described fossils formed a syntype series. By modern standards, from these a single specimen has to be selected to serve as
2875-459: A rather high position on the rear side and continued downwards to a point low on the front side of the shaft. The ischium is S-shaped in side view, showing at the transition point between the two curvatures a rough boss on the outer side. On the front edge of the ischial shaft an obturator process is present in the form of a low ridge, at its top separated from the shaft by a notch. To below, this ridge continues into an exceptionally thick bony skirt at
3000-511: A rough surface. The underside of the second sacral vertebra has an angular longitudinal keel. A ridge on the upper side of the third metatarsal connected to a groove in the side of the second metatarsal. The middle of the front edge of the scapula forms a thin crest. In 1824, Buckland assigned Megalosaurus to the Sauria, assuming within the Sauria a close affinity with modern lizards, more than with crocodiles. In 1842, Owen made Megalosaurus one of
3125-604: A separate group: the Dinosauria. Megalosaurus was thus one of the three original dinosaurs. In 1852, Benjamin Waterhouse Hawkins was commissioned to build a life-sized concrete model of Megalosaurus for the exhibition of prehistoric animals at the Crystal Palace Park in Sydenham, where it remains to this day. Hawkins worked under the direction of Owen and the statue reflected Owen's ideas that Megalosaurus would have been
3250-405: A single species. If so, several additional distinctive traits can be observed in other parts of the skeleton. The low vertical ridge on the outer side of the ilium, above the hip joint, shows parallel vertical grooves. The bony skirts between the shafts of the ischia are thick and touch each other forming an almost flat surface. There is a boss present on the lower outer side of the ischium shaft with
3375-593: A theropod skeleton in Oxford, arranging the known Megalosaurus bones, held by recesses in cardboard sheets, in a more or less natural position. During the 1870s, North American discoveries of large theropods, like Allosaurus , confirmed that they were bipedal. The Oxford University Museum of Natural History display contains most of the specimens from the original description by Buckland. The quarries at Stonesfield , which were worked until 1911, continued to produce Megalosaurus bucklandii fossils, mostly single bones from
3500-435: A variety of niches, beginning in the mid-Triassic 4 million to 6 million years after the extinction, and not fully proliferated until 30 million years after the extinction. Animal life was then dominated by various archosaurs: dinosaurs , pterosaurs, and aquatic reptiles such as ichthyosaurs, plesiosaurs, and mosasaurs . The climatic changes of the late Jurassic and Cretaceous favored further adaptive radiation. The Jurassic
3625-513: Is an extinct genus of large carnivorous theropod dinosaurs of the Middle Jurassic Epoch ( Bathonian stage, 166 million years ago) of southern England . Although fossils from other areas have been assigned to the genus, the only certain remains of Megalosaurus come from Oxfordshire and date to the late Middle Jurassic . The earliest remains of Megalosaurus were described in the 17th century, and were initially interpreted as
3750-708: Is equivalent to the Blood Reserve Formation of Alberta , Canada . The sediments of the Horsethief represent shallower water deposits than those of the Bearpaw Shale , adding further evidence that higher elevation areas existed to the south of the Two Medicine Formation's depositional area. This article about a specific stratigraphic formation in the United States is a stub . You can help Misplaced Pages by expanding it . Mesozoic The Mesozoic Era
3875-430: Is not known, making it impossible to determine whether the snout profile was curved or rectangular. A rather stubby snout is suggested by the fact that the front branch of the maxilla was short. In the depression around the antorbital fenestra to the front, a smaller non-piercing hollowing can be seen that is probably homologous to the fenestra maxillaris . The maxilla bears 13 teeth. The teeth are relatively large, with
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4000-597: Is now Europe during the Bathonian stage of the Middle Jurassic (~166-168 million years ago). Repeated descriptions during the nineteenth and early twentieth century of Megalosaurus hunting Iguanodon (another of the earliest dinosaurs named) through the forests that then covered the continent are now known to be inaccurate, because Iguanodon skeletons are found in much younger Early Cretaceous formations. The only specimens belonging to Megalosaurus bucklandii are from
4125-569: Is relatively straight, slightly curving inwards. To below, its shaft progressively flattens from front to rear, resulting in a generally oval cross-section. For about an eighth of its length the front lower end of the shaft is covered by a vertical branch of the astragalus . Of the foot, only the second, third and fourth metatarsals are known, the bone elements that were connected to the three weight-bearing toes. They are straight and robust, showing ligament pits at their lower sides. The third metatarsal has no clear condyles at its lower end, resulting in
4250-444: Is relatively wide and separated from the robust lesser trochanter in front of it, by a fissure. At the front base of the lesser trochanter a low accessory trochanter is present. At the lower end of the thigh bone a distinct front, extensor, groove separates the condyles . At the upper inner side of this groove a rough area is present continuing inwards into a longitudinal ridge, a typical megalosauroid trait. The shinbone , or tibia ,
4375-468: Is set by the Permian–Triassic extinction event , during which it has been estimated that up to 90-96% of marine species became extinct although those approximations have been brought into question with some paleontologists estimating the actual numbers as low as 81%. It is also known as the "Great Dying" because it is considered the largest mass extinction in the Earth's history. The upper boundary of
4500-477: Is the era of Earth's geological history , lasting from about 252 to 66 million years ago , comprising the Triassic , Jurassic and Cretaceous Periods . It is characterized by the dominance of gymnosperms such as cycads , ginkgoaceae and araucarian conifers, and of archosaurian reptiles such as the dinosaurs ; a hot greenhouse climate; and the tectonic break-up of Pangaea . The Mesozoic
4625-641: Is the middle of the three eras since complex life evolved : the Paleozoic , the Mesozoic, and the Cenozoic . The era began in the wake of the Permian–Triassic extinction event , the largest mass extinction in Earth's history, and ended with the Cretaceous–Paleogene extinction event , another mass extinction whose victims included the non-avian dinosaurs , pterosaurs , mosasaurs , and plesiosaurs . The Mesozoic
4750-522: Is thought that a large meteor smashed into earth 66 million years ago, creating the Chicxulub Crater in an event known as the K-Pg Extinction (formerly K-T), the fifth and most recent mass extinction event, in which 75% of life became extinct, including all non-avian dinosaurs. Compared to the vigorous convergent plate mountain-building of the late Paleozoic, Mesozoic tectonic deformation
4875-544: The French comparative anatomist Georges Cuvier visited Buckland in Oxford and realised that they were those of a giant lizard -like creature. Buckland further studied the remains with his friend William Conybeare who in 1821 referred to them as the "Huge Lizard". In 1822 Buckland and Conybeare, in a joint article to be included in Cuvier's Ossemens , intended to provide scientific names for both gigantic lizard-like creatures known at
5000-749: The Indian subcontinent , which collided with the Asian plate during the Cenozoic, giving rise to the Himalayas . The Triassic was generally dry, a trend that began in the late Carboniferous , and highly seasonal, especially in the interior of Pangaea. Low sea levels may have also exacerbated temperature extremes. With its high specific heat capacity , water acts as a temperature-stabilizing heat reservoir, and land areas near large bodies of water—especially oceans—experience less variation in temperature. Because much of Pangaea's land
5125-554: The Permian Period allowed for the radiation of many new lifeforms. In particular, the extinction of the large herbivorous pareiasaurs and carnivorous gorgonopsians left those ecological niches empty. Some were filled by the surviving cynodonts and dicynodonts , the latter of which subsequently became extinct. Recent research indicates that it took much longer for the reestablishment of complex ecosystems with high biodiversity, complex food webs, and specialized animals in
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5250-403: The nasal bone . Such a level of pneumatisation of the jugal is not known from other megalosaurids and might represent a separate autapomorphy . The lower jaw is rather robust. It is also straight in top view, without much expansion at the jaw tip, suggesting the lower jaws as a pair, the mandibula , were narrow. Several traits in 2008 identified as autapomorphies, later transpired to have been
5375-524: The pelvis and hindlimbs . Vertebrae and skull bones are rare. In 2010, Roger Benson counted a total of 103 specimens from the Stonesfield Slate, from a minimum of seven individuals. It has been contentious whether this material represents just a single taxon . In 2004, Julia Day and Paul Barrett claimed that there were two morphotypes present, based on small differences in the thighbones. In 2008 Benson favoured this idea, but in 2010 concluded
5500-421: The "lizard model" was entirely abandoned: they would have had an upright stance and a high metabolism. This also meant that earlier size estimates had been exaggerated. By simply adding the known length of the vertebrae, instead of extrapolating from a lizard, Owen arrived at a total body length for Megalosaurus of 30 feet. In the printed version of the lecture published in 1842, Owen united the three reptiles into
5625-453: The Atlantic seaway, which has grown continually larger until today. The further separation of the continents gave opportunity for the diversification of new dinosaurs. The Cretaceous is the longest period of the Mesozoic, but has only two epochs: Early and Late Cretaceous. The Early Cretaceous spans from 145 to 100 million years ago. The Early Cretaceous saw the expansion of seaways and
5750-513: The ICZN states that if a name has never been considered valid after 1899, it can be made a nomen oblitum , an invalid "forgotten name". In 1993, after the death of Halstead, his friend William A.S. Sarjeant submitted a petition to the International Commission on Zoological Nomenclature to formally suppress the name Scrotum in favour of Megalosaurus . He wrote that the supposed junior synonym Megalosaurus bucklandii should be made
5875-458: The Late Cretaceous declined for poorly understood reasons, though this might be due to tendencies of the fossil record, as their diversity seems to be much higher than previously thought. Birds became increasingly common and diversified into a variety of enantiornithe and ornithurine forms. Though mostly small, marine hesperornithes became relatively large and flightless, adapted to life in
6000-795: The Lower/Middle Bathonian of Oxfordshire and Gloucestershire. No material from outside the Bathonian formations of England can be referred to Megalosaurus . Other roughly contemporaneous dinosaur species known from the Bathonian of Britain include the theropods Cruxicheiros (a large sized taxon), Iliosuchus (a dubious taxon only known from fragmentary remains), the small tyrannosauroid Proceratosaurus , and other indeterminate theropods known from teeth, suggested to include dromaeosaurs , troodontids , and therizinosaurs , indeterminate ornithischians primarily known from teeth, including heterodontosaurids , stegosaurs , and ankylosaurs , and
6125-532: The Mesozoic is set at the Cretaceous–Paleogene extinction event (or K–Pg extinction event ), which may have been caused by an asteroid impactor that created Chicxulub Crater on the Yucatán Peninsula . Towards the Late Cretaceous, large volcanic eruptions are also believed to have contributed to the Cretaceous–Paleogene extinction event. Approximately 50% of all genera became extinct, including all of
6250-549: The Middle Jurassic, and the Late Jurassic. The Early Jurassic spans from 200 to 175 million years ago. The climate was tropical and much more humid than the Triassic, as a result of the large seas appearing between the land masses. In the oceans, plesiosaurs , ichthyosaurs and ammonites were abundant. On land, dinosaurs and other archosaurs staked their claim as the dominant race, with theropods such as Dilophosaurus at
6375-508: The Stonesfield Slate fossils perhaps belonged to several, possibly not directly related, species of theropod dinosaur. Subsequent research seemed to confirm this hypothesis, and the genus Megalosaurus and species M. bucklandii became generally regarded as limited to the taxon having produced the lectotype, the dentary of the lower jaw. Furthermore, several researchers failed to find any characteristics in that jaw that could be used to distinguish Megalosaurus from its relatives, which would mean
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#17328510304176500-648: The Taynton Limestone Formation, dating to the mid- Bathonian stage of the Jurassic Period. The bones were apparently acquired by William Buckland , Professor of Geology at the University of Oxford and dean of Christ Church . Buckland also studied a lower jaw, according to Gunther the one bought by Pegge. Buckland did not know to what animal the bones belonged but, in 1818, after the Napoleonic Wars ,
6625-468: The Tethys Ocean. Temperatures continued to increase, then began to stabilize. Humidity also increased with the proximity of water, and deserts retreated. The climate of the Cretaceous is less certain and more widely disputed. Probably, higher levels of carbon dioxide in the atmosphere are thought to have almost eliminated the north–south temperature gradient : temperatures were about the same across
6750-485: The attachment of the Musculus caudofemoralis brevis . The outer side of the rear blade does not match the inner side, which thus can be seen as a separate "medial blade" that in side view is visible in two places: in the corner between outer side and the ischial peduncle and as a small surface behind the extreme rear tip of the outer side of the rear blade. The pubic bone is straight. The pubic bones of both pelvis halves are connected via narrow bony skirts that originated at
6875-510: The beginnings of the breakup of Pangaea and the opening of the Tethys Ocean . Ecosystems had recovered from the Permian extinction. Algae, sponge, corals, and crustaceans all had recovered, and new aquatic reptiles evolved, such as ichthyosaurs and nothosaurs . On land, pine forests flourished, as did groups of insects such as mosquitoes and fruit flies. Reptiles began to get bigger and bigger, and
7000-425: The blade surface. The middle front edge over about 30% of its length is thinned, forming a slightly protruding crest. The scapula constitutes about half of the shoulder joint, which is orientated obliquely sideways and to below. The coracoid is in all known specimens fused with the scapula into a scapulocoracoid , lacking a visible suture . The coracoid as such is an oval bone plate, with its longest side attached to
7125-566: The centrum is strongly concave. The neck ribs are short. The front dorsal vertebrae are slightly opisthocoelous , with convex front centrum facets and concave rear centrum facets. They are also deeply keeled, with the ridge on the underside representing about 50% of the total centrum height. The front dorsals perhaps have a pleurocoel above the diapophysis , the lower rib joint process. The rear dorsal vertebrae, according to Benson, are not pneumatised. They are slightly amphicoelous, with hollow centrum facets. They have secondary joint processes, forming
7250-665: The concept of the transmutation of species as part of a general progressive development through time, as expressed in the work of Robert Chambers . In reaction, on 2 August 1841 Richard Owen during a lecture to the British Association for the Advancement of Science claimed that certain prehistoric reptilian groups had already attained the organisational level of present mammals, implying there had been no progress. Owen presented three examples of such higher level reptiles: Iguanodon , Hylaeosaurus and Megalosaurus . For these,
7375-399: The creature was 40 feet long and eight feet high. It is generally considered that the name in 1822 was still a nomen nudum ("naked name"). Buckland, urged on by an impatient Cuvier, continued to work on the subject during 1823, letting his later wife Mary Morland provide drawings of the bones, that were to be the basis of illustrating lithographies . Finally, on 20 February 1824, during
7500-431: The current level (about 21%) throughout the Mesozoic, some concluding they were lower in the Triassic and part of the Jurassic but higher in the Cretaceous, and some concluding they were higher throughout most or all of the Triassic, Jurassic and Cretaceous. The dominant land plant species of the time were gymnosperms , which are vascular, cone-bearing, non-flowering plants such as conifers that produce seeds without
7625-491: The dawn of the Mesozoic, ocean plankton communities transitioned from ones dominated by green archaeplastidans to ones dominated by endosymbiotic algae with red-algal-derived plastids. This transition is speculated to have been caused by an increasing paucity of many trace metals in the Mesozoic ocean. Megalosaurus Megalosaurus (meaning "great lizard", from Greek μέγας , megas , meaning 'big', 'tall' or 'great' and σαῦρος , sauros , meaning 'lizard')
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#17328510304177750-595: The differences were illusory. A maxilla fragment, specimen OUM J13506, was, in 1869 assigned, by Thomas Huxley , to M. bucklandii . In 1992 Robert Thomas Bakker claimed it represented a member of the Sinraptoridae ; in 2007, Darren Naish thought it was a separate species belonging to the Abelisauroidea . In 2010, Benson pointed out that the fragment was basically indistinguishable from other known M. bucklandii maxillae, to which it had in fact not been compared by
7875-600: The dramatic rifting of the supercontinent Pangaea, which gradually split into a northern continent, Laurasia , and a southern continent, Gondwana . This created the passive continental margin that characterizes most of the Atlantic coastline (such as along the U.S. East Coast ) today. By the end of the era, the continents had rifted into nearly their present forms, though not their present positions. Laurasia became North America and Eurasia , while Gondwana split into South America , Africa , Australia , Antarctica and
8000-413: The effects of allometry , heavier animals having relatively stouter bones, Buckland was forced in the printed version of his lecture to estimate the maximum length of Megalosaurus at 60 to 70 feet. The existence of Megalosaurus posed some problems for Christian orthodoxy , which typically held that suffering and death had only come into the world through Original Sin , which seemed irreconcilable with
8125-459: The end of the Cretaceous. Archaic birds appeared in the Jurassic, having evolved from a branch of theropod dinosaurs, then true toothless birds appeared in the Cretaceous. The first mammals also appeared during the Mesozoic, but would remain small—less than 15 kg (33 lb)—until the Cenozoic. Flowering plants appeared in the Early Cretaceous and would rapidly diversify through
8250-404: The end of the era, replacing conifers and other gymnosperms ( sensu lato ), such as ginkgoales , cycads and bennettitales as the dominant group of plants. The phrase "Age of Reptiles" was introduced by the 19th century paleontologist Gideon Mantell who viewed it as dominated by diapsids such as Iguanodon , Megalosaurus , Plesiosaurus , and Pterodactylus . The current name
8375-467: The fern prairies, chased by many new predators such as Allosaurus . Conifer forests made up a large portion of the forests. In the oceans, plesiosaurs were quite common, and ichthyosaurs flourished. This epoch was the peak of the reptiles. The Late Jurassic spans from 163 to 145 million years ago. During this epoch, the first avialans , such as Archaeopteryx , evolved from small coelurosaurian dinosaurs. The increase in sea levels opened up
8500-460: The first crocodilians and dinosaurs evolved, which sparked competition with the large amphibians that had previously ruled the freshwater world, respectively mammal-like reptiles on land. Following the bloom of the Middle Triassic, the Late Triassic, from 237 to 201 million years ago, featured frequent heat spells and moderate precipitation (10–20 inches per year). The recent warming led to
8625-552: The first finds, many other Megalosaurus bones have been recovered; however, no complete skeleton has yet been found. Therefore, the details of its physical appearance cannot be certain. However, a full osteology of all known material was published in 2010 by Benson. Traditionally, most texts, following Owen's estimate of 1841, give a body length of 30 feet or nine metres for Megalosaurus . The lack of an articulated dorsal vertebral series makes it difficult to determine an exact size. David Bruce Norman in 1984 thought Megalosaurus
8750-542: The first three genera placed in the Dinosauria . In 1850, Prince Charles Lucien Bonaparte coined a separate family Megalosauridae with Megalosaurus as the type genus . For a long time, the precise relationships of Megalosaurus remained vague. It was seen as a "primitive" member of the Carnosauria , the group in which most large theropods were united. In the late 20th century the new method of cladistics allowed for
8875-580: The first time to exactly calculate how closely various taxa were related to each other. In 2012, Matthew Carrano et al. showed that Megalosaurus was the sister species of Torvosaurus within the Megalosaurinae , giving this cladogram : Piatnitzkysauridae Streptospondylus Spinosauridae Eustreptospondylus Duriavenator Megalosaurus Torvosaurus Afrovenator Dubreuillosaurus Magnosaurus Leshansaurus Piveteausaurus Megalosaurus lived in what
9000-462: The flesh of its prey. The skeleton of Megalosaurus is highly ossified, indicating a robust and muscular animal, though the lower leg was not as heavily built as that of Torvosaurus , a close relative. The skull of Megalosaurus is poorly known. The discovered skull elements are generally rather large in relation to the rest of the material. This can either be coincidental or indicate that Megalosaurus had an uncommonly large head. The praemaxilla
9125-478: The food web. In the oceans, mosasaurs ruled, filling the role of the ichthyosaurs, which, after declining, had disappeared in the Cenomanian-Turonian boundary event . Though pliosaurs had gone extinct in the same event, long-necked plesiosaurs such as Elasmosaurus continued to thrive. Flowering plants, possibly appearing as far back as the Triassic, became truly dominant for the first time. Pterosaurs in
9250-411: The form Megalosaurus bucklandi was often used, a variant first published in 1832 by Christian Erich Hermann von Meyer – and sometimes erroneously ascribed to von Ritgen – but the more original M. bucklandii has priority. The first reconstruction was given by Buckland himself. He considered Megalosaurus to be a quadruped. He thought it was an "amphibian", i.e. an animal capable of both swimming in
9375-486: The fossil record. The Late Cretaceous spans from 100 to 66 million years ago. The Late Cretaceous featured a cooling trend that would continue in the Cenozoic Era. Eventually, tropics were restricted to the equator and areas beyond the tropic lines experienced extreme seasonal changes in weather. Dinosaurs still thrived, as new taxa such as Tyrannosaurus , Ankylosaurus , Triceratops and hadrosaurs dominated
9500-526: The fragment to Robert Plot , Professor of Chemistry at the University of Oxford and first curator of the Ashmolean Museum , who published a description and illustration in his Natural History of Oxfordshire in 1676. It was the first illustration of a dinosaur bone published. Plot correctly identified the bone as the lower extremity of the thighbone or femur of a large animal and he recognised that it
9625-406: The genus were a nomen dubium . However, a comprehensive study by Roger Benson and colleagues in 2008, and several related analyses published in subsequent years, overturned the previous consensus by identifying several autapomorphies , or unique distinguishing characteristics, in the lower jaw that could be used to separate Megalosaurus from other megalosaurids. Various distinguishing traits of
9750-399: The inner rear side of the shaft, covering over half of its length. Towards the end of the shaft, this skirt gradually merges with it. The shaft eventually ends in a sizeable "foot" with a convex lower profile. The thigh bone is straight in front view. Seen from the same direction its head is perpendicular to the shaft, seen from above it is orientated 20° to the front. The greater trochanter
9875-427: The lower jaw have been established. The longitudinal groove on the outer surface of the dentary is wide. The third tooth socket of the dentary is not enlarged. Seen from above, the dentary is straight without an expanded jaw tip. The interdental plates, reinforcing the teeth from behind, of the lower jaw are tall. Benson also concluded it would be most parsimonious to assume that the Stonesfield Slate material represents
10000-423: The maxilla are vertically grooved; the same combination is shown by Piatnitzkysaurus . The surangular has no bony shelf, or even ridge, on its outer side. There is laterally an oval opening present in front of the jaw joint, a foramen surangulare posterior , but a second foramen surangulare anterior to the front of it is lacking. Although the exact numbers are unknown, the vertebral column of Megalosaurus
10125-599: The non- avian dinosaurs. The Triassic ranges roughly from 252 million to 201 million years ago, preceding the Jurassic Period. The period is bracketed between the Permian–Triassic extinction event and the Triassic–Jurassic extinction event , two of the " big five ", and it is divided into three major epochs: Early, Middle, and Late Triassic. The Early Triassic, about 252 to 247 million years ago,
10250-412: The only true Megalosaurus species. Because a complete skeleton of it has never been found, much is still unclear about its build. The first naturalists who investigated Megalosaurus mistook it for a gigantic lizard 20 metres (66 ft) in length. In 1842, Owen concluded that it was no longer than 9 metres (30 ft). He still thought it was a quadruped, though. Modern scientists were able to obtain
10375-455: The open sea. Metatherians and primitive eutherian also became common and even produced large and specialised genera such as Didelphodon and Schowalteria . Still, the dominant mammals were multituberculates, cimolodonts in the north and gondwanatheres in the south. At the end of the Cretaceous, the Deccan traps and other volcanic eruptions were poisoning the atmosphere. As this continued, it
10500-502: The organism as being a giant animal belonging to the Sauria – the Lizards, at the time seen as including the crocodiles – and he placed it in the new genus Megalosaurus , repeating an estimate by Cuvier that the largest pieces he described, indicated an animal 12 metres long in life. Buckland had not provided a specific name , as was not uncommon in the early nineteenth century, when the genus
10625-554: The other authors. Apart from the finds in the Taynton Limestone Formation , in 1939 Sidney Hugh Reynolds referred remains to Megalosaurus that had been found in the older Chipping Norton Limestone Formation dating from the early Bathonian , about 30 single teeth and bones. Though the age disparity makes it problematic to assume an identity with Megalosaurus bucklandii , in 2009 Benson could not establish any relevant anatomical differences with M. bucklandii among
10750-437: The planet, and about 10° C higher than today. The circulation of oxygen to the deep ocean may also have been disrupted, preventing the decomposition of large volumes of organic matter, which was eventually deposited as " black shale ". Different studies have come to different conclusions about the amount of oxygen in the atmosphere during different parts of the Mesozoic, with some concluding oxygen levels were lower than
10875-641: The poles got seasonally colder, but some dinosaurs still inhabited the polar forests year round, such as Leaellynasaura and Muttaburrasaurus . The poles were too cold for crocodiles, and became the last stronghold for large amphibians such as Koolasuchus . Pterosaurs got larger as genera such as Tapejara and Ornithocheirus evolved. Mammals continued to expand their range: eutriconodonts produced fairly large, wolverine -like predators such as Repenomamus and Gobiconodon , early therians began to expand into metatherians and eutherians , and cimolodont multituberculates went on to become common in
11000-561: The possible type specimen of a new biological genus. According to the rules of the International Code of Zoological Nomenclature (ICZN), the name Scrotum humanum in principle had priority over Megalosaurus because it was published first. That Brookes understood that the stone did not actually represent a pair of petrified testicles was irrelevant. Merely the fact that the name had not been used in subsequent literature meant that it could be removed from competition for priority, because
11125-542: The presence of a gigantic devouring reptile during a pre-Adamitic phase of history. Buckland rejected the usual solution, that such carnivores would originally have been peaceful vegetarians, as infantile and claimed in one of the Bridgewater Treatises that Megalosaurus had played a beneficial role in creation by ending the lives of old and ill animals, "to diminish the aggregate amount of animal suffering". Around 1840, it became fashionable in England to espouse
11250-401: The public interest for prehistoric reptiles. Over 50 other species would eventually be classified under the genus; at first, this was because so few types of dinosaur had been identified, but the practice continued even into the 20th century after many other dinosaurs had been discovered. Today it is understood that none of these additional species was directly related to M. bucklandii , which is
11375-462: The remains found at one site, the New Park Quarry, and therefore affirmed the reference to that species. However, in another site, the Oakham Quarry, the material contained one bone, an ilium, that was clearly dissimilar. Sometimes trace fossils have been referred to Megalosaurus or to the ichnogenus Megalosauripus . In 1997, a famous group of fossilised footprints ( ichnites ) was found in
11500-518: The remains of elephants or giants. Megalosaurus was named in 1824 by William Buckland , becoming the first genus of non-avian dinosaur to be validly named. The type species is M. bucklandii , named in 1827 by Gideon Mantell , after Buckland. In 1842, Megalosaurus was one of three genera on which Richard Owen based his Dinosauria . On Owen's directions a model was made as one of the Crystal Palace Dinosaurs , which greatly increased
11625-470: The remains present at Oxford. Buckland had also been hurried into naming his new reptile by a visit he had made to the fossil collection of Mantell, who during the lecture announced to have acquired a fossil thigh bone of enormous magnitude, twice as long as that just described. Today, this is known to have belonged to Iguanodon , or at least some iguanodontid , but at the time both men assumed this bone belonged to Megalosaurus also. Even taking into account
11750-487: The result of damage. However, a unique combination of traits is present in the wide longitudinal groove on the outer side (shared with Torvosaurus ), the small third dentary tooth and a vascular channel, below the row of interdental plates, that only is closed from the fifth tooth position onwards. The number of dentary teeth was probably 13 or 14, though the preserved damaged specimens show at most 11 tooth sockets. The interdental plates have smooth inner sides, whereas those of
11875-416: The sacral vertebrae are rounded but the second sacral is keeled; normally it is the third or fourth sacral having a ridge. The sacral vertebrae seem not to be pneumatised but have excavations at their sides. The tail vertebrae are slightly amphicoelous, with hollow centrum facets on both the front and rear side. They have excavations at their sides and a longitudinal groove on the underside. The neural spines of
12000-623: The same meeting of the Geological Society of London in which Conybeare described a very complete specimen of Plesiosaurus , Buckland formally announced Megalosaurus . The descriptions of the bones in the Transactions of the Geological Society , in 1824, constitute a valid publication of the name. Megalosaurus was the first non-avian dinosaur genus named; the first of which the remains had with certainty been scientifically described
12125-435: The same year Benson claimed that Megalosaurus , though medium-sized, was still among the largest of Middle Jurassic theropods. Specimen NHMUK PV OR 31806, a thigh bone 803 millimetres long, would indicate a body weight of 943 kilogrammes, using the extrapolation method of J.F. Anderson — which method, optimised for mammals, tends to underestimate theropod masses by at least a third. Furthermore, thigh bone specimen OUM J13561 has
12250-428: The scapula. It is pierced by a large oval foramen but the usual boss for the attachment of the upper arm muscles is lacking. The humerus is very robust with strongly expanded upper and lower ends. Humerus specimen OUMNH J.13575 has a length of 388 millimetres. Its shaft circumference equals about half of the total humerus length. The humerus head continues to the front and the rear into large bosses, together forming
12375-442: The scientific literature. The earliest possible fossil of the genus, from the Taynton Limestone Formation , was the lower part of a femur , discovered in the 17th century. It was originally described by Robert Plot as a thigh bone of a Roman war elephant , and then as a biblical giant. Part of a bone was recovered from the Taynton Limestone Formation of Stonesfield limestone quarry, Oxfordshire in 1676. Sir Thomas Pennyson gave
12500-435: The sea and walking on land. Generally, in his mind Megalosaurus resembled a gigantic lizard, but Buckland already understood from the form of the thigh bone head that the legs were not so much sprawling as held rather upright. In the original description of 1824, Buckland repeated Cuvier's size estimate that Megalosaurus would have been 40 feet long with the weight of a seven foot tall elephant. However, this had been based on
12625-522: The similarity of Scrotum humanum to a modern species name, a so-called Linnaean " binomen " that has two parts, was not a coincidence. Linnaeus , the founder of modern taxonomy , had in the eighteenth century not merely devised a system for naming living creatures, but also for classifying geological objects. The book by Brookes was all about applying this latter system to curious stones found in England. According to Halstead, Brookes thus had deliberately used binomial nomenclature , and had in fact indicated
12750-462: The tail basis are transversely thin and tall, representing more than half of the total vertebral height. The shoulderblade or scapula is short and wide, its length about 6.8 times the minimum width; this is a rare and basal trait within Tetanurae. Its top curves slightly to the rear in side view. On the lower outer side of the blade a broad ridge is present, running from just below the shoulder joint to about mid-length where it gradually merges with
12875-501: The time: the remains found near Maastricht would be named Mosasaurus – then seen as a land-dwelling animal – while for the British lizard Conybeare had devised the name "Megalosaurus", from the Greek μέγας, megas , "large". That year a publication failed to occur, but the physician James Parkinson already in 1822 announced the name "Megalosaurus", illustrating one of the teeth and revealing
13000-497: The top of the food chain. The first true crocodiles evolved, pushing the large amphibians to near extinction. All-in-all, archosaurs rose to rule the world. Meanwhile, the first true mammals evolved, remaining relatively small, but spreading widely; the Jurassic Castorocauda , for example, had adaptations for swimming, digging and catching fish. Fruitafossor , from the late Jurassic Period about 150 million years ago,
13125-449: The tracks show no traits unique to Megalosaurus . Certainly they should be limited to finds that are of the same age as Megalosaurus bucklandii . Finds from sites outside England, especially in France, have in the nineteenth and twentieth century been referred to M. bucklandii . In 2010 Benson considered these as either clearly different or too fragmentary to establish an identity. Since
13250-409: The type specimen on which the name is based. In 1990, Ralph Molnar chose the famous dentary (front part of the lower jaw), OUM J13505 , as such a lectotype . Because he was unaccustomed to the deep dinosaurian pelvis, much taller than with typical reptiles, Buckland misidentified several bones, interpreting the pubic bone as a fibula and mistaking the ischium for a clavicle . Buckland identified
13375-415: Was Streptospondylus , in 1808 by Cuvier. By 1824, the material available to Buckland consisted of specimen OUM J13505, a piece of a right lower jaw with a single erupted tooth; OUM J13577, a posterior dorsal vertebra ; OUM J13579, an anterior caudal vertebra; OUM J13576, a sacrum of five sacral vertebrae; OUM J13585, a cervical rib; OUM J13580, a rib; OUM J29881, an ilium of the pelvis , OUM J13563,
13500-572: Was a time of significant tectonic, climatic, and evolutionary activity. The supercontinent Pangaea began to break apart into separate landmasses. The climate of the Mesozoic was varied, alternating between warming and cooling periods. Overall, however, the Earth was hotter than it is today. Dinosaurs first appeared in the Mid-Triassic, and became the dominant terrestrial vertebrates in the Late Triassic or Early Jurassic, occupying this position for about 150 or 135 million years until their demise at
13625-531: Was about the size of a chipmunk, and its teeth, forelimbs and back suggest that it dug open the nests of social insects (probably termites , as ants had not yet appeared) ; Volaticotherium was able to glide for short distances, such as modern flying squirrels . The first multituberculates such as Rugosodon evolved. The Middle Jurassic spans from 175 to 163 million years ago. During this epoch, dinosaurs flourished as huge herds of sauropods, such as Brachiosaurus and Diplodocus , filled
13750-877: Was comparatively mild. The sole major Mesozoic orogeny occurred in what is now the Arctic , creating the Innuitian orogeny , the Brooks Range , the Verkhoyansk and Cherskiy Ranges in Siberia, and the Khingan Mountains in Manchuria. This orogeny was related to the opening of the Arctic Ocean and suturing of the North China and Siberian cratons to Asia. In contrast, the era featured
13875-523: Was distant from its shores, temperatures fluctuated greatly, and the interior probably included expansive deserts . Abundant red beds and evaporites such as halite support these conclusions, but some evidence suggests the generally dry climate of the Triassic was punctuated by episodes of increased rainfall. The most important humid episodes were the Carnian Pluvial Event and one in the Rhaetian ,
14000-533: Was dominated by deserts in the interior of the Pangaea supercontinent. The Earth had just witnessed a massive die-off in which 95% of all life became extinct, and the most common vertebrate life on land were Lystrosaurus , labyrinthodonts , and Euparkeria along with many other creatures that managed to survive the Permian extinction. Temnospondyls reached peak diversity during the early Triassic. The Middle Triassic, from 247 to 237 million years ago, featured
14125-401: Was first challenged by the find of Compsognathus in 1859. That, however, was a very small animal, the significance of which for gigantic forms could be denied. In 1870, near Oxford, the type specimen of Eustreptospondylus was discovered – the first reasonably intact skeleton of a large theropod. It was clearly bipedal. Shortly afterwards, John Phillips created the first public display of
14250-497: Was generally a robust and heavily muscled animal. At the time Megalosaurus lived, Europe formed an island archipelago around the Tethys Ocean , with Megalosaurus inhabiting an island formed by the London–Brabant Massif , where it likely served as the apex predator of its ecosystem, coexisting with other dinosaurs like the large sauropod Cetiosaurus . In 1699, Edward Lhuyd described what he believed to have been
14375-525: Was given the very first species name ever applied to an extinct dinosaur. Plot's engraving of the Cornwell bone was again used in a book by Richard Brookes in 1763. Brookes, in a caption, called it " Scrotum humanum", apparently comparing its appearance to a pair of "human testicles ". However, it is possible that the attribution of this name stemmed from illustrator error, not Richard Brookes. In 1970, paleontologist Lambert Beverly Halstead pointed out that
14500-424: Was not confidently assigned to Megalosaurus until the tooth was re-described by Delair & Sarjeant (2002). OU 1328 was collected near Caswell, near Witney , Oxfordshire sometime during the 17th century and became the third dinosaur fossil to ever be illustrated, after "Scrotum humanum" in 1677 and "Rutellum impicatum" in 1699. Megalosaurus may have been the first non avian dinosaur to be described in
14625-505: Was originally described as the "secondary" era, following the "primary" ( Paleozoic ), and preceding the Tertiary . Following the Paleozoic, the Mesozoic extended roughly 186 million years, from 251.902 to 66 million years ago when the Cenozoic Era began. This time frame is separated into three geologic periods . From oldest to youngest: The lower boundary of the Mesozoic
14750-504: Was probably divided into 10 neck vertebrae, 13 dorsal vertebrae, five sacral vertebrae and 50 to 60 tail vertebrae, as is common for basal Tetanurae . The Stonesfield Slate material contains no neck vertebrae; but a single broken anterior cervical vertebra is known from the New Park Quarry, specimen NHMUK PV R9674. The breakage reveals large internal air chambers. The vertebra is also otherwise heavily pneumatised, with large pleurocoels , pneumatic excavations, on its sides. The rear facet of
14875-527: Was proposed in 1840 by the British geologist John Phillips (1800–1874). "Mesozoic" literally means 'middle life', deriving from the Greek prefix meso- ( μεσο- 'between') and zōon ( ζῷον 'animal, living being'). In this way, the Mesozoic is comparable to the Cenozoic ( lit. ' new life ' ) and Paleozoic ('old life') eras as well as the Proterozoic ('earlier life') Eon. The Mesozoic Era
15000-434: Was seven to eight metres long. Gregory S. Paul in 1988 estimated the weight tentatively at 1.1 tonnes, given a thigh bone 76 centimetres long. The trend in the early twenty-first century to limit the material to the lectotype inspired even lower estimates, disregarding outliers of uncertain identity. Paul in 2010 estimated the size of Megalosaurus at 6 metres (20 ft) in length and 700 kilograms (1,500 lb). However,
15125-578: Was still dominated by cycads and ferns until after the Cretaceous–Paleogene extinction. Some plant species had distributions that were markedly different from succeeding periods; for example, the Schizeales , a fern order, were skewed to the Northern Hemisphere in the Mesozoic, but are now better represented in the Southern Hemisphere. The extinction of nearly all animal species at the end of
15250-451: Was still seen as the more essential concept. In 1826, Ferdinand von Ritgen gave this dinosaur a complete binomial, Megalosaurus conybeari , which however was not much used by later authors and is now considered a nomen oblitum . A year later, in 1827, Gideon Mantell included Megalosaurus in his geological survey of southeastern England, and assigned the species its current valid binomial name, Megalosaurus bucklandii . Until recently,
15375-485: Was the height of archosaur diversity, and the first birds and eutherian mammals also appeared. Some have argued that insects diversified in symbiosis with angiosperms, because insect anatomy , especially the mouth parts, seems particularly well-suited for flowering plants. However, all major insect mouth parts preceded angiosperms, and insect diversification actually slowed when they arrived, so their anatomy originally must have been suited for some other purpose. At
15500-419: Was too incomplete to definitely be referred to Megalosaurus and not a different, contemporary theropod. During the last part of the eighteenth century, the number of fossils in British collections quickly increased. According to a hypothesis published by science historian Robert Gunther in 1925, among them was a partial lower jaw of Megalosaurus . It was discovered about 40 feet (12 m) underground in
15625-469: Was too large to belong to any species known to be living in England. He therefore at first concluded it to be the thigh bone of a Roman war elephant and later that of a giant human, such as those mentioned in the Bible. The bone has since been lost, but the illustration is detailed enough that some have since identified it as that of Megalosaurus . It has also been argued that this possible Megalosaurus bone
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