116-489: Dinosauromorpha is a clade of avemetatarsalians ( archosaurs closer to birds than to crocodilians) that includes the Dinosauria (dinosaurs) and some of their close relatives. It was originally defined to include dinosauriforms and lagerpetids , with later formulations specifically excluding pterosaurs from the group. Birds are the only dinosauromorphs which survive to the present day. The name "Dinosauromorpha"
232-592: 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
348-532: 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
464-463: 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
580-478: 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
696-588: A population , or a species ( extinct or extant ). Clades are nested, one in another, as each branch in turn splits into smaller branches. These splits reflect evolutionary history as populations diverged and evolved independently. Clades are termed monophyletic (Greek: "one clan") groups. Over the last few decades, the cladistic approach has revolutionized biological classification and revealed surprising evolutionary relationships among organisms. Increasingly, taxonomists try to avoid naming taxa that are not clades; that is, taxa that are not monophyletic . Some of
812-558: A silesaurid which may have lived as early as the Anisian age of the middle Triassic period, about 245 million years ago, although it is possible that Nyasasaurus is a dinosaur of the same age, pushing the origins of the groups back further. Putative basal dinosauromorphs include Saltopus , Marasuchus , the perhaps identical Lagosuchus , the lagerpetid Lagerpeton from the Ladinian of Argentina and Dromomeron from
928-479: A "ladder", with supposedly more "advanced" organisms at the top. Taxonomists have increasingly worked to make the taxonomic system reflect evolution. When it comes to naming , this principle is not always compatible with the traditional rank-based nomenclature (in which only taxa associated with a rank can be named) because not enough ranks exist to name a long series of nested clades. For these and other reasons, phylogenetic nomenclature has been developed; it
1044-402: 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
1160-446: A branch of mammals that split off after the end of the period when the clade Dinosauria stopped being the dominant terrestrial vertebrates 66 million years ago. The original population and all its descendants are a clade. The rodent clade corresponds to the order Rodentia, and insects to the class Insecta. These clades include smaller clades, such as chipmunk or ant , each of which consists of even smaller clades. The clade "rodent"
1276-1057: A carnivorous form, was found to be the most primitive form of ornithischian, which was almost universally considered to be an only-herbivorous clade before. Dinosauromorpha was reduced to only including Lagerpetidae and Lagosuchus as a result of the reclassification of silesaurids. Below are the results of: Cau (2018, parsimony results): Lagerpetidae Marasuchus Silesauridae Dinosauria Cau (2018, bayesian results): Marasuchus Lagerpetidae Teleocrater Silesauridae Herrerasauria Dinosauria Ezcurra et al. (2020): Lagerpetidae Pterosauria Lagosuchus Silesauridae Dinosauria Müller and Garcia (2020): Lagerpetidae Lagosuchus Saurischia Ornithischia (incl. silesaurids) A variety of individual species and taxa have at times been found to place within Dinosauromorpha and its subgroups, but outside Dinosauria. The taxon Marasuchus has been consistently recovered as
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#17327910482741392-623: A clade can be described based on two different reference points, crown age and stem age. The crown age of a clade refers to the age of the most recent common ancestor of all of the species in the clade. The stem age of a clade refers to the time that the ancestral lineage of the clade diverged from its sister clade. A clade's stem age is either the same as or older than its crown age. Ages of clades cannot be directly observed. They are inferred, either from stratigraphy of fossils , or from molecular clock estimates. Viruses , and particularly RNA viruses form clades. These are useful in tracking
1508-401: 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
1624-407: A dinosauromorph between lagerpetids and silesaurids, but may also be a junior synonym of the coexisting form Lagosuchus , another dinosauromorph. Pisanosaurus , traditionally considered an ornithischian, was recovered in an unpublished analysis as a dinosauriform outside other clades, but has since been recovered only as a member of Silesauridae or Ornithischia. Saltopus , an enigmatic taxon from
1740-485: 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
1856-441: 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
1972-490: 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
2088-671: 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
2204-510: 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
2320-483: 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
2436-409: 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
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#17327910482742552-586: A node-based clade containing the most recent common ancestor of Lagosuchus and Dinosauria, and all its descendants. Nesbitt (2011) provided a roughly equivalent definition, using Marasuchus and Passer domesticus (the house sparrow, a representative of dinosaurs). In his analysis, Dinosauriformes included dinosaurs, silesaurids , and Marasuchus , but not lagerpetids , which were considered to be an earlier-branching family of dinosauromorphs. A phylogenetic analysis by Andrea Cau in 2018 resolved two different topologies for dinosaur origins, depending on whether it
2668-402: 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
2784-430: 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
2900-459: 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
3016-422: A revised taxonomy based on a concept strongly resembling clades, although the term clade itself would not be coined until 1957 by his grandson, Julian Huxley . German biologist Emil Hans Willi Hennig (1913–1976) is considered to be the founder of cladistics . He proposed a classification system that represented repeated branchings of the family tree, as opposed to the previous systems, which put organisms on
3132-515: 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
3248-623: 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
3364-403: A silesaurid, or a basal saurischian. The genus Nyasasaurus from the early Late Triassic of Tanzania is known from multiple incomplete specimens, making it difficult to classify. It has been found as the direct sister taxon of Dinosauria, the basalmost ornithischian, a basal theropod, or a deeply-nested sauropodomorph. Dinosauromorphs appeared putatively around 242 to 244 million years ago by
3480-405: 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
3596-429: A suffix added should be e.g. "dracohortian". A clade is by definition monophyletic , meaning that it contains one ancestor which can be an organism, a population, or a species and all its descendants. The ancestor can be known or unknown; any and all members of a clade can be extant or extinct. The science that tries to reconstruct phylogenetic trees and thus discover clades is called phylogenetics or cladistics ,
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3712-531: A synonym of the silesaurid Lewisuchus ), Dinosauria (including Aves), and all its descendants. This definition was intended to correspond to a clade including lagerpetids and crownward bird-line archosaurs, but not pterosaurs or other archosaurs. In 2011, Dinosauromorpha was redefined by Sterling Nesbitt to be a branch-based clade, defined by including reptiles closer to one group than to another. Under this definition, Dinosauromorpha included all reptiles closer to dinosaurs (represented by Passer domesticus ,
3828-597: 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
3944-546: Is a grouping of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree . In the taxonomical literature, sometimes the Latin form cladus (plural cladi ) is used rather than the English form. Clades are the fundamental unit of cladistics , a modern approach to taxonomy adopted by most biological fields. The common ancestor may be an individual,
4060-522: 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
4176-476: Is in turn included in the mammal, vertebrate and animal clades. The idea of a clade did not exist in pre- Darwinian Linnaean taxonomy , which was based by necessity only on internal or external morphological similarities between organisms. Many of the better known animal groups in Linnaeus's original Systema Naturae (mostly vertebrate groups) do represent clades. The phenomenon of convergent evolution
4292-430: 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
4408-609: 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
4524-569: 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
4640-444: 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 ,
4756-515: Is responsible for many cases of misleading similarities in the morphology of groups that evolved from different lineages. With the increasing realization in the first half of the 19th century that species had changed and split through the ages, classification increasingly came to be seen as branches on the evolutionary tree of life . The publication of Darwin's theory of evolution in 1859 gave this view increasing weight. In 1876 Thomas Henry Huxley , an early advocate of evolutionary theory, proposed
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4872-489: Is still controversial. As an example, see the full current classification of Anas platyrhynchos (the mallard duck) with 40 clades from Eukaryota down by following this Wikispecies link and clicking on "Expand". The name of a clade is conventionally a plural, where the singular refers to each member individually. A unique exception is the reptile clade Dracohors , which was made by haplology from Latin "draco" and "cohors", i.e. "the dragon cohort "; its form with
4988-574: The Anisian stage of the Middle Triassic , splitting from other ornithodires. Early Triassic footprints reported in October 2010 from the Świętokrzyskie (Holy Cross) Mountains of Poland may belong to a dinosauromorph. If so, the origin of dinosauromorphs would be pushed back into the Early Olenekian , around 249 Ma. The oldest Polish footprints are from a small quadrupedal animal named Prorotodactylus , but footprints belonging to
5104-552: 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
5220-527: The Late Triassic of Scotland , has been placed closer to dinosaurs than Marasuchus , in a polytomy with Silesauridae and Dinosauria, as a sister taxon to Marasuchus , or within Dinosauria as a basal saurischian. The British taxon Agnosphitys was originally described as a dinosauriform closer to Dinosauria than Herrerasaurus , but has also been classified as a dinosauriform more derived than silesaurids but basal to Herrerasauridae and Dinosauria,
5336-733: The Norian of Arizona , New Mexico , and Texas (all in the United States), Ixalerpeton polesinensis and an unnamed form from the Carnian ( Santa Maria Formation ) of Brazil , and the silesaurids , which include Silesaurus from the Carnian of Poland , Eucoelophysis from the Carnian-Norian of New Mexico, Lewisuchus and the perhaps identical Pseudolagosuchus from the Ladinian of Argentina , Sacisaurus from
5452-528: The ichnogenus Sphingopus that have been found from Early Anisian strata show that moderately large bipedal dinosauromorphs had appeared by 246 Ma. The tracks show that the dinosaur lineage appeared soon after the Permian-Triassic extinction event . Their age suggests that the rise of dinosaurs was slow and drawn out across much of the Triassic. The oldest known dinosauromorph is Asilisaurus ,
5568-403: 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
5684-532: 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
5800-421: 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
5916-475: The 1980s. The group encompassed by Gauthier's "Ornithosuchia" and Benton's "Dinosauromorpha" is now given the name Avemetatarsalia . In 1991, Paul Sereno redefined Dinosauromorpha as a node-based clade , defined by a last common ancestor and its descendants. In his definition, Dinosauromorpha included the last common ancestor of Lagerpeton (a lagerpetid ), Marasuchus (a possible junior synonym of Lagosuchus ), Pseudolagosuchus (now considered
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#17327910482746032-523: 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
6148-810: 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
6264-575: The Norian of Brazil , Technosaurus from the Carnian of Texas, Asilisaurus from the Anisian of Tanzania , and Diodorus from the Carnian(?) to Norian of Morocco . [REDACTED] [REDACTED] [REDACTED] Clade In biological phylogenetics , a clade (from Ancient Greek κλάδος (kládos) 'branch'), also known as a monophyletic group or natural group ,
6380-508: 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
6496-679: 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 ,
6612-485: 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
6728-442: The axial epipophyses, the centrodiapophyseal laminae in the presacral vertebrae, the relative size enlargement of the postacetabular process of ilium, the elongation of the pubis, the proximal sulcus and the reduction of the ligament tuber in the femoral head, and the further reduction in length of the fourth metatarsal and toe compared to the third. Following the discovery and description of more cranial and postcranial material of
6844-425: 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
6960-566: 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
7076-680: 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,
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#17327910482747192-399: 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
7308-609: 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
7424-413: 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
7540-552: 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
7656-496: 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
7772-587: 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
7888-462: 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
8004-411: 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
8120-540: 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
8236-493: The genera Kongonaphon , Ixalerpeton and Lagerpeton , it was found that lagerpetids shared many features with the basal taxa of Pterosauria . Features of the maxillary bone , teeth, braincase and forelimb meant that the 2020 phylogenetic analysis of Ezcurra and colleagues placed Lagerpetidae next to pterosaurs within Pterosauromorpha, removing the family from Dinosauromorpha. The contents of Dinosauromorpha
8352-406: 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
8468-583: The group Ornithodira , which encompasses almost all avemetatarsalians. Dinosauriformes was coined in 1992 by F.E. Novas, who used it to encompass dinosaurs, Lagosuchus , " Pseudolagosuchus " (= Lewisuchus ), and the herrerasaurids , which he did not consider to be "eudinosaurs" (true dinosaurs like ornithischians and saurischians ). Contrary to Novas, most paleontologists since 1992 have considered herrerasaurids to be true dinosaurs, though many other dinosaur-like reptiles still fall within his definition of Dinosauriformes. Novas (1992) defined Dinosauriformes as
8584-575: The groups Herrerasauria , Sauropodomorpha , Theropoda and Ornithischia , along with the basal form Eodromaeus . However, under bayesian results, Herrerasauria placed outside Dinosauria within Dracohors, and Dinosauriformes, Dinosauromorpha, and Pan-Aves were synonyms, with Marasuchus in a clade with lagerpetids. Pisanosaurus was resolved within Silesauridae. Cau identified the synapomorphies of Dracohors as: The anterior tympanic recess,
8700-471: The house sparrow), rather than pterosaurs (represented by Pterodactylus ), ornithosuchids (represented by Ornithosuchus ), or other pseudosuchians (represented by Crocodylus niloticus , the Nile crocodile). Nesbitt's study supported the hypothesis that Pterosauromorpha (pterosaurs and their potential relatives) was the sister group of Dinosauromorpha. Pterosauromorphs and dinosauromorphs together formed
8816-399: 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
8932-518: The latter term coined by Ernst Mayr (1965), derived from "clade". The results of phylogenetic/cladistic analyses are tree-shaped diagrams called cladograms ; they, and all their branches, are phylogenetic hypotheses. Three methods of defining clades are featured in phylogenetic nomenclature : node-, stem-, and apomorphy-based (see Phylogenetic nomenclature§Phylogenetic definitions of clade names for detailed definitions). The relationship between clades can be described in several ways: The age of
9048-427: 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
9164-423: 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
9280-412: 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
9396-511: 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
9512-565: 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
9628-569: 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
9744-551: 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
9860-401: 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
9976-482: The relationships between organisms that the molecular biology arm of cladistics has revealed include that fungi are closer relatives to animals than they are to plants, archaea are now considered different from bacteria , and multicellular organisms may have evolved from archaea. The term "clade" is also used with a similar meaning in other fields besides biology, such as historical linguistics ; see Cladistics § In disciplines other than biology . The term "clade"
10092-469: 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
10208-528: 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
10324-470: 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
10440-487: 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
10556-416: 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
10672-645: 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
10788-435: 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
10904-428: 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
11020-442: 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
11136-435: 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
11252-522: 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
11368-558: The spread of viral infections . HIV , for example, has clades called subtypes, which vary in geographical prevalence. HIV subtype (clade) B, for example is predominant in Europe, the Americas and Japan, whereas subtype A is more common in east Africa. Megalosaurus bucklandi Megalosaurus (meaning "great lizard", from Greek μέγας , megas , meaning 'big', 'tall' or 'great' and σαῦρος , sauros , meaning 'lizard')
11484-462: 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
11600-510: 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
11716-453: 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
11832-409: 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
11948-415: 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,
12064-433: Was briefly coined by Michael J. Benton in 1985. It was considered an alternative name for the group "Ornithosuchia", which was named by Jacques Gauthier to correspond to archosaurs closer to dinosaurs than to crocodilians. Although "Ornithosuchia" was later recognized as a misnomer (since ornithosuchids are now considered closer to crocodilians than to dinosaurs), it was still a more popular term than Dinosauromorpha in
12180-423: Was coined in 1957 by the biologist Julian Huxley to refer to the result of cladogenesis , the evolutionary splitting of a parent species into two distinct species, a concept Huxley borrowed from Bernhard Rensch . Many commonly named groups – rodents and insects , for example – are clades because, in each case, the group consists of a common ancestor with all its descendant branches. Rodents, for example, are
12296-401: 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
12412-557: 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
12528-530: 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
12644-424: 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
12760-504: 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
12876-405: Was run using parsimony or bayesian inference . Cau coined the term Dracohors for the clade uniting all taxa closer to the theropod Megalosaurus bucklandi than the basal form Marasuchus lilloensis . The name is derived from the Latin words for "dragon" and "cohort", draco and cohors . Under parsimony results, Dracohors included only Silesauridae and Dinosauria , the latter including
12992-434: 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,
13108-451: 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,
13224-650: Was thus restricted to only Silesauridae, Dinosauria, and individual genera like Lagosuchus . Simultaneously, Rodrigo Müller and Maurício Garcia published novel results that reduced the family Silesauridae to a grade of basal dinosaurs in Ornithischia . Pisanosaurus , considered by various authors to be either a silesaurid or basal ornithischian, was found to be intermediate between the grade of silesaurids and true ornithischians, explaining its peculiar combination of silesaurid and ornithischian features that has resulted in its phylogenetic inconsistency. Lewisuchus ,
13340-419: 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
13456-473: 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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