Poekilopleuron

Poekilopleuron (meaning "varied ribs") is an extinct genus of megalosauroid tetanuran theropod dinosaur, which lived during the middle Bathonian of the Jurassic, about 168 to 166 million years ago. The genus has been used under many different spelling variants, although only one, Poekilopleuron, is valid. The type species is P. bucklandii, named after William Buckland, and many junior synonyms of it have also been erected. Few material is currently known, as the holotype was destroyed in World War II, although many casts of the material still exist.

Poekilopleuron
Temporal range: Middle Jurassic, 167.7–166.1 Ma
Gastralia
Cast of the holotype gastralia, Muséum National d'Histoire Naturelle
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Theropoda
Family: Megalosauridae
Subfamily: Afrovenatorinae
Genus: Poekilopleuron
Eudes-Deslongchamps, 1836
Type species
Poekilopleuron bucklandii
Eudes-Deslongchamps, 1836
Synonyms[1]

Discovery and naming

Falaise en Normandie
Geography of Normandy, France, where remains of Poekilopleuron have been found

Poekilopleuron is a genus of theropod with a long and complex history. The genus was first named and described by Jacques-Amand Eudes-Deslongchamps in a report published in 1836,[2][3] based on holotype material that is now destroyed. In 1837, Eudes-Deslongchamps published a more detailed account of this discovery in a monograph[4] which was also inserted next year in volume 6 of the "Mémoires de la Société Linnéenne Normandie".[5]

The holotype, which was housed in Musée de la Faculté des Sciences de Caen and destroyed during World War II, included gastralia, phalanges, a left forelimb, caudal vertebrae, chevrons, ribs and a hindlimb. Of all the material, few is still preserved, although the gastralia, phalanges and forelimb were cast and now represent the plastotype, with casts in the Muséum National d'Histoire Naturelle (specimen MNHN 1897-2) and Yale Peabody Museum (specimen YPM 4938). The original material was uncovered in a layer of the Calcaire de Caen in Normandy, France. Poekilopleuron can be assigned to the middle Bathonian in age,[1] about 167.7 to 166 million years ago.[6]

Poekilopleuron neural spine
Megalosauroid neural arch and spine referred by Owen to Poekilopleuron.

In the same 1836 publication, Eudes-Deslongchamps also named the type species of Poekilopleuron, P. bucklandii.[2][3] Eudes-Deslongchapms noted similarities with some material of Megalosaurus bucklandii and Poekilopleuron, and chose the species name bucklandii for Poekilopleuron, so that it the two genera were synonymized, only the genus name would be suppressed.[1] The generic name is derived from Greek ποίκιλος, poikilos, "varied", and πλευρών, pleuron, "rib", a reference to the three types of rib present. The specific name, honouring William Buckland, was deliberately identical to that of Megalosaurus bucklandii.

Description

Poekilopleuron size
Size of Poekilopleuron compared to a human

The most distinctive feature of Poekilopleuron were its forelimbs. Their length, about 60 cm, was a sign of this theropod's more original build. Unlike later Theropoda, whose forelimbs tended toward reduction in length in proportion to the animals' size, Poekilopleuron's were long and, by implication, potent. The length mostly resided in the elongated but powerfully muscled humerus. The antebrachia (forearms) were markedly short and robust, a characteristic shared with Poekilopleuron's slightly later and considerably larger American cousin Torvosaurus. A unique feature is a lack of the olecranon process on the ulna.[1]

The fossil of Poekilopleuron showed a rare complete set of gastralia: fourteen pair of belly ribs supported the body of the animal.[1]

Classification

Poekilopleuron is a difficult taxon to classify, as its original material is lost, and few casts are known. Poekilopleuron has a history of being renamed under different species and genera, most of which are now its junior synonyms.[1]

Eudes-Deslongchamps thought the specimen might well be proven to belong to this earlier named species; if so, merely the generic name would have to be changed. Indeed, following 1879 Poekilopleuron was often subsumed under Megalosaurus bucklandii.[7] Eudes-Deslongchamps' choice caused problems however, when Friedrich von Huene in 1923 concluded it was part of Megalosaurus but as a separate species within that genus. As both species carried the same epithet bucklandii, they could no longer be distinguished. Von Huene therefore renamed the species into Megalosaurus poekilopleuron. Most later authors continued using the generic name Poekilopleuron.

Another problem was caused by the fact that the name was only partially Latinised. In correct Greek it would have been "poikilopleuron", in Latin "poecilopleurum". This induced later writers to improve the spelling, leading to such variants as Poecilopleuron and Poikilopleuron (still used as late as 2006). However, the original name has priority and is valid.

Five other species would be named in the genus. In 1869 Edward Drinker Cope renamed Laelaps gallicus into Poekilopleuron gallicum. In 1870 Joseph Leidy created a Poicilopleuron valens based on a fossil probably belonging to Allosaurus.[8] In 1876 Richard Owen named a Poikilopleuron pusillus, in 1879 renamed by Cope to Poekilopleuron minor; in 1887 Harry Govier Seeley made it a separate genus: Aristosuchus.[9] In 1883 W.A. Kiprijanow created a Poekilopleuron schmidti, of which the specific name honours Friedrich Schmidt, based on some indeterminate ribs and a sauropod metatarsal.[10] This chimaera is a nomen dubium. A much later named species is Poekilopleuron valesdunensis created by Ronan Allain in 2002.[11] In 2005 it was renamed Dubreuillosaurus.[12]

Poekilopleuron life restoration
Life restoration of two Poekilopleuron

Because the original fossil was destroyed and no other remains of Poekilopleuron have since been found, and also because of its name change, there is much controversy surrounding its classification that cannot be resolved. Traditionally it has been assigned to the Megalosauridae, but some recent analyses showed a position in the Sinraptoridae; others had as result it was a member of Megalosauroidea, in a basal position or in the Eustreptospondylinae. Benson et al. (2010) found it and Lourinhanosaurus to belong to Sinraptoridae.[13] An earlier study found that it was a primitive allosauroid outside Sinraptoridae.[14]

Paleobiology

The material of Poekilopleuron bucklandii includes two tail vertebrae with the chevron of one vertebra ankylosed to the centrum of the next within the development of an exostosis. Two phalanges also preserve pathologies. One probable pedal phalanx shows three low, irregular exostosis-like projections. A second probable manual phalanx exhibits a "low rounded projection resembling a callus." Ralph Molnar considered the occurrence of three pathologies in one individual to be "noteworthy". Sadly the specimens cannot be examined further to determine the etiology of the pathologies because of their destruction during the British bombing raid in 1944.[15]

References

  1. ^ a b c d e f Allain R.; Chure D. J. (2002). "Poekilopleuron bucklandii, the theropod dinosaur from the Middle Jurassic (Bathonian) of Normandy" (PDF). Palaeontology. 45 (6): 1107–1121. doi:10.1111/1475-4983.00277.
  2. ^ a b Eudes-Deslongchamps J.-A. (1836). "Plusieurs parties d'un mémoire sur un très-grand animal fossile découvert, l'an dernier, dans les carrières de la Maladrerie à un quart de lieu de Caen". Analyse des Travaux de la Société Pendant l'Année Académique 1835–1836, Séance Publique de la Société Linnéenne de Normandie Tenue à Vire le 24 Mai 1836: 14–25.
  3. ^ a b Brignon A. (2018). "New historical data on the first dinosaurs found in France". BSGF - Earth Sciences Bulletin. 189 (4): 4. doi:10.1051/bsgf/2018003.
  4. ^ Eudes-Deslongchamps J.-A. (1837) Mémoire sur le Poekilopleuron bucklandii, grand saurien fossile, intermédiaire entre les crocodiles et les lézards. A. Hardel, Caen, 114 p., 8 pl.
  5. ^ Eudes-Deslongchamps J.-A. (1838). "Mémoire sur le Poekilopleuron bucklandii, grande saurien fossile, intermédiaire entre les crocodiles et les lézards, découvert dans les carrières de la Maladrerie, près Caen, au mois de juillet 1835". Mémoires de la Société Linnéenne Normandie. 6: 37–146, 8 pl.
  6. ^ Holtz, T.R. Jr (2012). "Updated genus list for Holtz (2007) Dinosaurs" (PDF). University of Maryland. p. 8.
  7. ^ Hulke J.W. (1879). "Note on Poekilopleuron bucklandi of Eudes Deslongchamps (père), identifying it with Megalosaurus bucklandi". Quarterly Journal of the Geological Society. 35 (1–4): 233–238. doi:10.1144/GSL.JGS.1879.035.01-04.10.
  8. ^ Leidy J (1870). "Remarks on Poicilopleuron valens, Clidastes intermedius, Leiodon proriger, Baptemys wyomingensis, and Emys stevensonianus". Proceedings of the Academy of Natural Sciences. 22 (1): 3–4. JSTOR 4624064.
  9. ^ Seeley H.G. (1887). "On Aristosuchus pusillus Owen, being further notes on the fossils described by Sir R. Owen as Poikilopleuron pusillus Owen". Quarterly Journal of the Geological Society of London. 43 (1–4): 221–228. doi:10.1144/GSL.JGS.1887.043.01-04.22.
  10. ^ Kiprijanow W.A. (1883). "Studien über die Fossilen Reptilien Russlands. IV. Theil. Ordnung Crocodilia Oppel. Indeterminierte Fossile Reptilien". Mémoires de l'Académie Impériale des Sciences de Saint-Pétersbourg. VIIe série. 31 (7): 1–29.
  11. ^ Allain R (2002). "Discovery of megalosaur (Dinosauria, Theropoda) in the Middle Bathonian of Normandy (France) and its implications for the phylogeny of basal Tetanurae". Journal of Vertebrate Paleontology. 22 (3): 548–563. doi:10.1671/0272-4634(2002)022[0548:DOMDTI]2.0.CO;2.
  12. ^ Allain R (2005). "The postcranial anatomy of the megalosaur Dubreuillosaurus valesdunensis (Dinosauria: Theropoda) from the Middle Jurassic of Normandy, France". Journal of Vertebrate Paleontology. 25 (4): 850–858. doi:10.1671/0272-4634(2005)025[0850:TPAOTM]2.0.CO;2.
  13. ^ Benson, R.B.J., Carrano, M.T and Brusatte, S.L. (2010). "A new clade of archaic large-bodied predatory dinosaurs (Theropoda: Allosauroidea) that survived to the latest Mesozoic". Naturwissenschaften. 97 (1): 71–78. Bibcode:2010NW.....97...71B. doi:10.1007/s00114-009-0614-x. PMID 19826771.CS1 maint: Multiple names: authors list (link) Supporting Information
  14. ^ Allain R (2001). "Redescription de Streptospondylus altdorfensis, le dinosaure théropode de Cuvier, du Jurassique de Normandie [Redescription of Streptospondylus altdorfensis, Cuvier's theropod dinosaur from the Jurassic of Normandy]" (PDF). Geodiversitas. 23 (3): 349–367.
  15. ^ Molnar, R. E., 2001, Theropod paleopathology: a literature survey: In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, p. 337-363.
1836 in paleontology

Paleontology or palaeontology is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. This includes the study of body fossils, tracks (ichnites), burrows, cast-off parts, fossilised feces (coprolites), palynomorphs and chemical residues. Because humans have encountered fossils for millennia, paleontology has a long history both before and after becoming formalized as a science. This article records significant discoveries and events related to paleontology that occurred or were published in the year 1836.

1944 in paleontology

Paleontology or palaeontology is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. This includes the study of body fossils, tracks (ichnites), burrows, cast-off parts, fossilised feces (coprolites), palynomorphs and chemical residues. Because humans have encountered fossils for millennia, paleontology has a long history both before and after becoming formalized as a science. This article records significant discoveries and events related to paleontology that occurred or were published in the year 1944.

Afrovenator

Afrovenator (; "African hunter") is a genus of megalosaurid theropod dinosaur from the middle Jurassic Period of northern Africa.

Allosauroidea

Allosauroidea is a superfamily or clade of theropod dinosaurs which contains four families — the Metriacanthosauridae, Allosauridae, Carcharodontosauridae, and Neovenatoridae. Allosauroids, alongside the family Megalosauroidea, were among the apex predators that were active during the Middle Jurassic to Late Cretaceous periods. Of the fourteen allosauroid taxa, five are known for specimens with relatively complete skulls; the taxa are Allosaurus, Sinraptor, Yangchuanosaurus, Carchardontosaurus, and Acrocanthosaurus. The most famous and best understood allosauroid is the North American genus Allosaurus.

The oldest-known allosauroid, Shidaisaurus jinae, appeared in the early Middle Jurassic (probably Bajocian stage) of China. The last known definitive surviving members of the group died out around 93 million years ago in Asia (Shaochilong) and South America (Mapusaurus), though the megaraptorans may belong to the group as well. Additional, but highly fragmentary, remains probably belonging to carcharodontosaurids have been found from the Late Maastrichtian (70-66 Ma ago) in Brazil. An alternative interpretation is to attribute the remains to abelisaurids, which share the distinct pattern of curved wrinkled enamel found in the Brazilian remains with the carcharodontosaurids. This similarity between abelisaurids and carcharodontosaurids means that a definitive match between the Brazilian fossil and carcharodontosaurids cannot be made.Allosauroids had long, narrow skulls, large orbits, three-fingered hands, and usually had "horns" or ornamental crests on their heads. Although allosauroids vary in size, the group maintains a similar center of mass and hip position on their bodies. Allosauroids also exhibit reptilian-style immune systems, secreting fibrin at injured sites to prevent infections from spreading through the bloodstream. This characteristic has been observed by examining injuries and infections on allosauroid bones. It is possible that allosauroids were social animals, as many remains of allosauroids have been found in close proximity to each other. Allosauroids were likely active predators, and from studying endocasts, probably best responded to odors and loud low-frequency noises.

Ankylosis

Ankylosis is a stiffness of a joint due to abnormal adhesion and rigidity of the bones of the joint, which may be the result of injury or disease. The rigidity may be complete or partial and may be due to inflammation of the tendinous or muscular structures outside the joint or of the tissues of the joint itself.When the structures outside the joint are affected, the term "false ankylosis" has been used in contradistinction to "true ankylosis", in which the disease is within the joint. When inflammation has caused the joint-ends of the bones to be fused together, the ankylosis is termed osseous or complete and is an instance of synostosis. Excision of a completely ankylosed shoulder or elbow may restore free mobility and usefulness to the limb. "Ankylosis" is also used as an anatomical term, bones being said to ankylose (or anchylose) when, from being originally distinct, they coalesce, or become so joined together that no motion can take place between them.The term is from Greek ἀγκύλος, bent, crooked.

Antrodemus

Antrodemus ("chamber bodied") is a dubious genus of theropod dinosaur from the Kimmeridgian-Tithonian-age Upper Jurassic Morrison Formation of Middle Park, Colorado. It contains one species, Antrodemus valens, first described and named as a species of Poekilopleuron by Joseph Leidy in 1870.

The first described fossil specimen was a bone obtained secondhand by Ferdinand Vandiveer Hayden in 1869. It came from Middle Park, near Granby, Colorado, probably from Morrison Formation rocks. The locals had identified such bones as petrified horse hooves. Hayden sent his specimen to Joseph Leidy, who identified it as half of a tail vertebra, and tentatively assigned it to the European dinosaur genus Poekilopleuron as Poicilopleuron [sic] valens. He later decided it deserved its own genus, Antrodemus.In 1920, Charles W. Gilmore came to the conclusion that the tail vertebra named Antrodemus by Leidy was indistinguishable from those of Allosaurus, and that Antrodemus should be the preferred name because, as the older name, it had priority. Antrodemus became the accepted name for this familiar genus for over fifty years, until James Madsen published on the Cleveland-Lloyd specimens of Allosaurus and concluded that name should be used because Antrodemus was based on material with poor, if any, diagnostic features and locality information (for example, the geological formation that the single bone of Antrodemus came from is unknown). Subsequent authors have agreed with this assessment and have considered Antrodemus a nomen dubium.

Aristosuchus

Aristosuchus was a small coelurosaurian dinosaur whose name was derived from the Greek ἄριστος (meaning bravest, best, noblest) and σουχος (the Ancient Greek corruption of the name of the Egyptian crocodile-headed god Sobek). It shared many characteristics with birds.

Bathonian

In the geologic timescale the Bathonian is an age and stage of the Middle Jurassic. It lasted from approximately 168.3 Ma to around 166.1 Ma (million years ago). The Bathonian age succeeds the Bajocian age and precedes the Callovian age.

Calcaire de Caen

The Calcaire de Caen or Caen Limestone is a geological formation in France. It dates back to the mid-Bathonian of the Jurassic. It was often quarried for building work and is referred to as Caen Stone.

Dubreuillosaurus

Dubreuillosaurus is a genus of carnivorous dinosaur from the middle Jurassic Period. It is a megalosaurid theropod. Its fossils were found in France. The only named species, Dubreuillosaurus valesdunensis, was originally described as a species of Poekilopleuron, Poekilopleuron? valesdunensis, which is still formally the type species of the genus. It was later renamed Dubreuillosaurus valesdunensis when, in 2005, Allain came to the conclusion that it was not part of the genus Poekilopleuron. Its type specimen, MNHN 1998-13, is only rivalled in the number of preserved elements in this group by that of Eustreptospondylus. Dubreuillosaurus is considered to be the sister species of Magnosaurus. It did not show signs of insular dwarfism even though it was uncovered on an island.

Exostosis

An exostosis (pronounced ek·sow·stow·suhs and derived from ex- meaning outside and osteon- meaning bone), also known as bone spur, is the formation of new bone on the surface of a bone. Exostoses can cause chronic pain ranging from mild to debilitatingly severe, depending on the shape, size, and location of the lesion. It is most commonly found in places like the ribs, where small bone growths form, but sometimes larger growths can grow on places like the ankles, knees, shoulders, elbows and hips. Very rarely are they on the skull.

Exostoses are sometimes shaped like spurs, such as calcaneal spurs.

Osteomyelitis, a bone infection, may leave the adjacent bone with exostosis formation. Charcot foot, the neuropathic breakdown of the feet seen primarily in diabetics, can also leave bone spurs that may then become symptomatic.

They normally form on the bones of joints, and can grow upwards. For example, if an extra bone formed on the ankle, it might grow up to the shin.

When used in the phrases "cartilaginous exostosis" or "osteocartilaginous exostosis", the term is considered synonymous with osteochondroma. Some sources consider the two terms to mean the same thing even without qualifiers, but this interpretation is not universal.

Jacques Amand Eudes-Deslongchamps

Jacques Amand Eudes-Deslongchamps (17 January 1794 – 17 January 1867) was a French naturalist and paleontologist. His son, Eugène Eudes-Deslongchamps (1830–1889), was also a paleontologist.He was born at Caen in Normandy. His parents, though poor, contrived to give him a good education, and he studied medicine in his native town to such good effect that in 1812 he was appointed assistant-surgeon in the navy, and in 1815 surgeon assistant major to the military hospital of Caen. Soon afterwards he proceeded to Paris to qualify for the degree of doctor of surgery, and there the researches and teachings of Cuvier attracted his attention to subjects of natural history and palaeontology.In 1822 he was elected surgeon to the board of relief at Caen, and while he never ceased to devote his energies to the duties of this post, he sought relaxation in geological studies. Soon he discovered remains of Teleosaurus in one of the Caen quarries, and he became an ardent palaeontologist. He was one of the founders of the museum of natural history at Caen, and acted as honorary curator; he was likewise one of the founders of the Socité linnenne de Normandie (1823), to the transactions of which society he communicated papers on Teleosaurus, Poekilopleuron (Megalosaurus), on Jurassic mollusca and brachiopoda. In 1825 he became professor of zoology to the faculty of sciences, and in 1847, dean.

Lourinhanosaurus

Lourinhanosaurus (meaning "Lourinhã lizard") was a genus of carnivorous theropod dinosaur that lived during the Late Jurassic Period (Kimmeridgian/Tithonian) in Portugal. It is one of many large predators discovered at the Lourinhã Formation and probably competed with coeval Torvosaurus gurneyi, Allosaurus europaeus, and Ceratosaurus.

Megalosauridae

Megalosauridae is a monophyletic family of carnivorous theropod dinosaurs within the order Megalosauroidea, closely related to the family Spinosauridae. Some members of this family include Megalosaurus, Torvosaurus, Eustreptospondylus, and Afrovenator. Appearing in the Middle Jurassic, megalosaurids were among the first major radiation of large theropod dinosaurs, although they became extinct by the end of the Jurassic period. They were a relatively primitive group of basal tetanurans containing two main subfamilies, Megalosaurinae and Afrovenatorinae, along with the basal genus Eustreptospondylus, an unresolved taxon which differs from both subfamilies.The defining megalosaurid is Megalosaurus bucklandii, first named and described in 1824 by William Buckland after multiple finds in Stonesfield, Oxfordshire, UK. Megalosaurus was the first formally described dinosaur and was the basis for the establishment of the clade Dinosauria. It is also one of the largest known Middle Jurassic carnivorous dinosaurs, with the best-preserved femur at 805 mm and a proposed body mass of around 943 kg. Megalosauridae is recognized as a mainly European group of dinosaurs, based on fossils found in France and the UK. However, recent discoveries in Niger have led some to consider the range of the family. Megalosaurids appeared right before the split of the supercontinent Pangaea into Gondwana and Laurasia. These large theropods therefore may have dominated both halves of the world during the Jurassic.The family Megalosauridae was first defined by Thomas Huxley in 1869, yet it has been contested throughout history due to its role as a ‘waste-basket’ for many partially described dinosaurs or unidentified remains. In the early years of paleontology, most large theropods were grouped together and up to 48 species were included in the clade Megalosauria, the basal clade of Megalosauridae. Over time, most of these taxa were placed in other clades and the parameters of Megalosauridae were narrowed significantly. However, some controversy remains over whether Megalosauridae should be considered its own distinct group, and dinosaurs in this family remain some of the most problematic taxa in all Dinosauria. Some paleontologists, such as Paul Sereno in 2005, have disregarded the group due to its shaky foundation and lack of clarified phylogeny. However, recent research by Carrano, Benson, and Sampson has systematically analyzed all basal tetanurans and determined that Megalosauridae should exist as its own family.

Megalosauroidea

Megalosauroidea (meaning 'great/big lizard forms') is a superfamily (or clade) of tetanuran theropod dinosaurs that lived from the Middle Jurassic to the Late Cretaceous period. The group is defined as Megalosaurus bucklandii and all taxa sharing a more recent common ancestor with it than with Allosaurus fragilis or Passer domesticus. Members of the group include Spinosaurus, Megalosaurus, and Torvosaurus.

Megalosaurus

Megalosaurus (meaning "Great Lizard", from Greek μέγας, megas, meaning 'big', 'tall' or 'great' and σαῦρος, sauros, meaning 'lizard') is an extinct genus of large meat-eating theropod dinosaurs of the Middle Jurassic period (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 possible fossils of the genus came from the Taynton Limestone Formation. One of these was the lower part of a femur, discovered in the 17th century. It was originally described by Robert Plot as a thighbone of a Roman war elephant, and then as a biblical giant. The first scientific name given for it, in the 18th century, was Scrotum humanum, created by Richard Brookes as a caption; however, this is not considered valid today.

Megalosaurus was, in 1824, the first genus of non-avian dinosaur to be validly named. The type species is Megalosaurus bucklandii, named in 1827. 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 the public interest for prehistoric reptiles. Subsequently, over fifty other species would be classified under the genus, originally because dinosaurs were not well known, but even during the 20th century after many dinosaurs had been discovered. Today it is understood these additional species were not directly related to M. bucklandii, which is 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 of twenty metres length. In 1842, Owen concluded that it was no longer than nine metres, standing on upright legs. He still thought it was a quadruped, though. Modern scientists, by comparing Megalosaurus with its direct relatives in the Megalosauridae, were able to obtain a more accurate picture. Megalosaurus was about six metres long, weighing about seven hundred kilogrammes. 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 was generally a robust and heavily muscled animal.

Metriacanthosauridae

Metriacanthosauridae is an extinct family of theropod dinosaurs that lived from the Middle Jurassic to the Early Cretaceous. When broken down into its Greek roots, it means "moderately-spined lizards". The family is split into two subgroups: Metriacanthosaurinae, which includes dinosaurs closely related to Metriacanthosaurus, and another group composed of the close relatives of Yangchuanosaurus. Metriacanthosaurids are considered carnosaurs, belonging to the Allosauroidea superfamily. The group includes species of large range in body size. Of their physical traits, most notable are their neural spines. Their fossils can be found mostly in the Northern hemisphere. Metriacanthosauridae is used as a senior synonym of Sinraptoridae.

Ornithoscelida

Ornithoscelida () is a clade that includes various major groupings of dinosaurs. An order Ornithoscelida was originally proposed by Thomas Henry Huxley but later abandoned in favor of Harry Govier Seeley's division of Dinosauria into Saurischia and Ornithischia. The term was revived in 2017 after a new cladistic analysis by Baron et al.

Piatnitzkysauridae

Piatnitzkysauridae is an extinct family of megalosauroid dinosaurs. It consists of three known dinosaur genera: Condorraptor, Marshosaurus, and Piatnitzkysaurus. The most complete and well known member of this family is Piatnitzkysaurus, which also gives the family its name.

Piatnitzkysauridae
Megalosauria

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