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172-808: Allosaurus ( / ˌ æ l ə ˈ s ɔːr ə s / ) is an extinct genus of large carnosaurian theropod dinosaur that lived 155 to 145 million years ago during the Late Jurassic period ( Kimmeridgian to late Tithonian ages ). The name " Allosaurus " means "different lizard", alluding to its unique (at the time of its discovery) concave vertebrae . It is derived from the Greek words ἄλλος ( allos ) ("different", "strange", or "other") and σαῦρος ( sauros ) ("lizard" or "reptile"). The first fossil remains that could definitively be ascribed to this genus were described in 1877 by famed paleontologist Othniel Charles Marsh . The genus has

344-438: A food chain who lose their prey. "Species coextinction is a manifestation of one of the interconnectednesses of organisms in complex ecosystems ... While coextinction may not be the most important cause of species extinctions, it is certainly an insidious one." Coextinction is especially common when a keystone species goes extinct. Models suggest that coextinction is the most common form of biodiversity loss . There may be

516-811: A jugal (cheekbone) with a straight lower margin. Fossils are confined to the Salt Wash Member of the Morrison Formation, with A. fragilis only found in the higher Brushy Basin Member. A. fragilis , A. jimmadseni , A. amplus , and A. lucasi are all known from remains discovered in the Kimmeridgian – Tithonian Upper Jurassic -age Morrison Formation of the United States, spread across Colorado , Montana , New Mexico , Oklahoma , South Dakota , Utah and Wyoming . A. fragilis

688-710: A natural history museum at Yale . While studying at the University of Berlin in late 1863, the 32-year-old Marsh first met 25-year-old Edward Drinker Cope , who was also on a scientific tour of Europe. Cope had much less formal schooling than Marsh, but had already published thirty-seven papers. The two Americans spent a few days together and would become friends. After a salmon fishing excursion with Peabody in Ireland, Marsh returned to America in July or August 1865. Marsh had expected Peabody's gift would have resulted in

860-669: A nautilus to the Royal Society that was more than two feet in diameter, and morphologically distinct from any known living species. Hooke theorized that this was simply because the species lived in the deep ocean and no one had discovered them yet. While he contended that it was possible a species could be "lost", he thought this highly unlikely. Similarly, in 1695, Sir Thomas Molyneux published an account of enormous antlers found in Ireland that did not belong to any extant taxa in that area. Molyneux reasoned that they came from

1032-415: A species or a population is the variety of genetic information in its living members. A large gene pool (extensive genetic diversity ) is associated with robust populations that can survive bouts of intense selection . Meanwhile, low genetic diversity (see inbreeding and population bottlenecks ) reduces the range of adaptions possible. Replacing native with alien genes narrows genetic diversity within

1204-436: A viable population for species preservation and possible future reintroduction to the wild, through use of carefully planned breeding programs . The extinction of one species' wild population can have knock-on effects, causing further extinctions. These are also called "chains of extinction". This is especially common with extinction of keystone species . A 2018 study indicated that the sixth mass extinction started in

1376-479: A Lazarus species when extant individuals were described in 2019. Attenborough's long-beaked echidna ( Zaglossus attenboroughi ) is an example of a Lazarus species from Papua New Guinea that had last been sighted in 1962 and believed to be possibly extinct, until it was recorded again in November 2023. Some species currently thought to be extinct have had continued speculation that they may still exist, and in

1548-695: A carcharodontosaurian or megalosaurid. Although obscure, it was a large theropod, possibly around 10 metres (33 ft) long and 2.5 tonnes (2.5 long tons; 2.8 short tons) in weight. Kurzanov and colleagues in 2003 designated six teeth from Siberia as Allosaurus sp. (meaning the authors found the specimens to be most like those of Allosaurus , but did not or could not assign a species to them). They were reclassified as an indeterminate theropod. Also, reports of Allosaurus in Shanxi , China go back to at least 1982. These were interpreted as Torvosaurus remains in 2012. An astragalus (ankle bone) thought to belong to

1720-503: A cascade of coextinction across the trophic levels . Such effects are most severe in mutualistic and parasitic relationships. An example of coextinction is the Haast's eagle and the moa : the Haast's eagle was a predator that became extinct because its food source became extinct. The moa were several species of flightless birds that were a food source for the Haast's eagle. Extinction as

1892-429: A common ancestor with modern horses. Pseudoextinction is much easier to demonstrate for larger taxonomic groups. A Lazarus taxon or Lazarus species refers to instances where a species or taxon was thought to be extinct, but was later rediscovered. It can also refer to instances where large gaps in the fossil record of a taxon result in fossils reappearing much later, although the taxon may have ultimately become extinct at

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2064-647: A couple of pieces of the skull, portions of nine tail vertebrae, two hip vertebrae, an ilium , and ankle and foot bones. Although the idea of two common Morrison allosaur species was followed in some semi-technical and popular works, the 2000 thesis on Allosauridae noted that Charles Gilmore mistakenly reconstructed USNM 4734 as having a shorter skull than the specimens referred by Paul to atrox , refuting supposed differences between USNM 4734 and putative A. atrox specimens like DINO 2560, AMNH 600, and AMNH 666. "Allosaurus agilis", seen in Zittel, 1887 , and Osborn, 1912 ,

2236-514: A different genus. However, they found that the specimen was undiagnostic, and thus A. lucaris was a nomen dubium . Allosaurus sibiricus was described in 1914 by A. N. Riabinin on the basis of a bone, later identified as a partial fourth metatarsal, from the Early Cretaceous of Buryatia , Russia. It was transferred to Chilantaisaurus in 1990, but is now considered a nomen dubium indeterminate beyond Theropoda. Allosaurus meriani

2408-399: A fact that was accepted by most scientists. The primary debate focused on whether this turnover caused by extinction was gradual or abrupt in nature. Cuvier understood extinction to be the result of cataclysmic events that wipe out huge numbers of species, as opposed to the gradual decline of a species over time. His catastrophic view of the nature of extinction garnered him many opponents in

2580-470: A fifth (outermost) metatarsal , perhaps used as a lever between the Achilles tendon and foot. Skin impressions from Allosaurus have been described. One impression, from a juvenile specimen, measures 30 cm² and is associated with the anterior dorsal ribs/pectoral region. The impression shows small scales measuring 1–3 mm in diameter. A skin impression from the "Big Al Two" specimen, associated with

2752-708: A higher risk of extinction and die out faster than less sexually dimorphic species, the least sexually dimorphic species surviving for millions of years while the most sexually dimorphic species die out within mere thousands of years. Earlier studies based on counting the number of currently living species in modern taxa have shown a higher number of species in more sexually dimorphic taxa which have been interpreted as higher survival in taxa with more sexual selection, but such studies of modern species only measure indirect effects of extinction and are subject to error sources such as dying and doomed taxa speciating more due to splitting of habitat ranges into more small isolated groups during

2924-516: A hundred new species of vertebrate fossils. After 1876, Marsh employed bone hunters who shipped specimens back to him; he did not return west himself until 1879. When Cope began prospecting for fossils in the Bridger Basin, which Marsh considered "his" territory, their relationship deteriorated into hostility. Marsh served as Vertebrate Paleontologist of the U.S. Geological Survey from 1882 to 1892. Thanks to John Wesley Powell , head of

3096-438: A joint. Allosaurus had nine vertebrae in the neck, 14 in the back, and five in the sacrum supporting the hips. The number of tail vertebrae is unknown and varied with individual size; James Madsen estimated about 50, while Gregory S. Paul considered that to be too many and suggested 45 or less. There were hollow spaces in the neck and anterior back vertebrae. Such spaces, which are also found in modern theropods (that is,

3268-405: A large range, a lack of individuals of both sexes (in sexually reproducing species), or other reasons. Pinpointing the extinction (or pseudoextinction ) of a species requires a clear definition of that species . If it is to be declared extinct, the species in question must be uniquely distinguishable from any ancestor or daughter species, and from any other closely related species. Extinction of

3440-607: A later point. The coelacanth , a fish related to lungfish and tetrapods , is an example of a Lazarus taxon that was known only from the fossil record and was considered to have been extinct since the end of the Cretaceous Period . In 1938, however, a living specimen was found off the Chalumna River (now Tyolomnqa) on the east coast of South Africa. Calliostoma bullatum , a species of deepwater sea snail originally described from fossils in 1844 proved to be

3612-594: A mathematical model that falls in all positions. By contrast, conservation biology uses the extinction vortex model to classify extinctions by cause. When concerns about human extinction have been raised, for example in Sir Martin Rees ' 2003 book Our Final Hour , those concerns lie with the effects of climate change or technological disaster. Human-driven extinction started as humans migrated out of Africa more than 60,000 years ago. Currently, environmental groups and some governments are concerned with

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3784-480: A meeting of the American Association, Marsh elected to join other members to Omaha on a "geological excursion"; it was Marsh's first trip to the far western United States, and it inspired him to return to prospect. Marsh organized a series of private expeditions starting in 1870 to 1874, with the prospecting groups composed of Yale students or recent graduates. The first of these uncovered more than

3956-456: A natural part of the evolutionary process. Only recently have extinctions been recorded and scientists have become alarmed at the current high rate of extinctions . Most species that become extinct are never scientifically documented. Some scientists estimate that up to half of presently existing plant and animal species may become extinct by 2100. A 2018 report indicated that the phylogenetic diversity of 300 mammalian species erased during

4128-441: A new mega-predator or by transporting animals and plants from one part of the world to another. Such introductions have been occurring for thousands of years, sometimes intentionally (e.g. livestock released by sailors on islands as a future source of food) and sometimes accidentally (e.g. rats escaping from boats). In most cases, the introductions are unsuccessful, but when an invasive alien species does become established,

4300-626: A painting by Charles R. Knight . Although notable as the first free-standing mount of a theropod dinosaur and often illustrated and photographed, it has never been scientifically described. The multiplicity of early names complicated later research, with the situation compounded by the terse descriptions provided by Marsh and Cope. Even at the time, authors such as Samuel Wendell Williston suggested that too many names had been coined. For example, Williston pointed out in 1901 that Marsh had never been able to adequately distinguish Allosaurus from Creosaurus . The most influential early attempt to sort out

4472-564: A petition to the ICZN to have the name A. fragilis officially transferred to the more complete specimen USNM4734 (as a neotype ), a decision that was ratified by the ICZN on December 29, 2023. Creosaurus , Epanterias , and Labrosaurus are regarded as junior synonyms of Allosaurus . Most of the species that are regarded as synonyms of A. fragilis , or that were misassigned to the genus, are obscure and based on very scrappy remains. One exception

4644-610: A population a higher chance in the short term of surviving an adverse change in conditions. Effects that cause or reward a loss in genetic diversity can increase the chances of extinction of a species. Population bottlenecks can dramatically reduce genetic diversity by severely limiting the number of reproducing individuals and make inbreeding more frequent. Extinction sometimes results for species evolved to specific ecologies that are subjected to genetic pollution —i.e., uncontrolled hybridization , introgression and genetic swamping that lead to homogenization or out-competition from

4816-440: A position at Yale, but it took until 1866 when Yale established a chair of paleontology at the university. Marsh was given the position, but no salary was attached; biographer George Grinnell suggested that this suited Marsh just fine, as he was more interested in research than teaching. Marsh's interests shifted entirely to paleontology, and after 1869 his other scientific contributions mostly ceased. While teaching, Marsh toured

4988-419: A professor of science. While in graduate school, Marsh published his first scientific papers on minerals and vertebrate fossils from his Nova Scotia trips, which possibly inspired Marsh's interest in vertebrate paleontology. He obtained his masters degree in 1862. Following school, Marsh declined a professorship at Yale and instead took a tour of Europe; it is possible the trip was to avoid being drafted into

5160-407: A race of animals to become extinct. A series of fossils were discovered in the late 17th century that appeared unlike any living species. As a result, the scientific community embarked on a voyage of creative rationalization, seeking to understand what had happened to these species within a framework that did not account for total extinction. In October 1686, Robert Hooke presented an impression of

5332-649: A range from approximately 1.4 t (1.5 short tons) to approximately 2 t (2.2 short tons). A separate computational project estimated the adaptive optimum body mass in Allosaurus to be ~2,345 kg. A. europaeus has been measured up to 7 m (23 ft) in length and 1 t (1.1 short tons) in body mass. Several gigantic specimens have been attributed to Allosaurus , but may in fact belong to other genera. The closely related genus Saurophaganax ( OMNH 1708) reached perhaps 10.5 m (34 ft) in length, and its single species has sometimes been included in

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5504-454: A range of bone sizes which he interpreted to show a maximum length of 12 to 13 m (39 to 43 ft). As with dinosaurs in general, weight estimates are debatable, and since 1980 have ranged between 1.5 t (1.7 short tons), 1 to 4 t (1.1 to 4.4 short tons), and approximately 1 metric ton (1.1 short tons) for modal adult weight (not maximum). John Foster , a specialist on the Morrison Formation, suggests that 1 t (1.1 short tons)

5676-992: A record 1400 scientific papers. Marsh named the following dinosaur genera : He named the suborders Ceratopsia (1890), Ceratosauria (1884), Ornithopoda (1881), Stegosauria (1877), and Theropoda (1881). He also named the families Allosauridae (1878), Anchisauridae (1885), Camptosauridae (1885), Ceratopsidae (1890), Ceratosauridae , Coeluridae , Diplodocidae (1884), Dryptosauridae (1890), Nodosauridae (1890), Ornithomimidae (1890), Plateosauridae (1895), and Stegosauridae (1880). Marsh dubbed many additional species of dinosaur as well, notable taxa including Allosaurus fragilis , Triceratops horridus , Stegosaurus stenops , Ornithomimus velox , and Brontosaurus excelsus . Dinosaurs named by others in honour of Marsh include Hoplitosaurus marshi (Lucas, 1901), Iaceornis marshi (Clarke, 2004), Marshosaurus (Madsen, 1976), Othnielia (Galton, 1977), and Othnielosaurus (Galton, 2007). Marsh's finds formed

5848-502: A reduction in agricultural productivity. Furthermore, increased erosion contributes to poorer water quality by elevating the levels of sediment and pollutants in rivers and streams. Habitat degradation through toxicity can kill off a species very rapidly, by killing all living members through contamination or sterilizing them. It can also occur over longer periods at lower toxicity levels by affecting life span, reproductive capacity, or competitiveness. Habitat degradation can also take

6020-499: A result of climate change has been confirmed by fossil studies. Particularly, the extinction of amphibians during the Carboniferous Rainforest Collapse , 305 million years ago. A 2003 review across 14 biodiversity research centers predicted that, because of climate change, 15–37% of land species would be "committed to extinction" by 2050. The ecologically rich areas that would potentially suffer

6192-399: A single tooth. Because of this, several scientists have interpreted the type specimen as potentially dubious, meaning the genus Allosaurus itself or at least the species A. fragilis would be a nomen dubium ("dubious name", based on a specimen too incomplete to compare to other specimens or to classify). To address this situation, Gregory S. Paul and Kenneth Carpenter ( 2010 ) submitted

6364-400: A skull belonging to an individual he estimates at 7.9 m (26 ft) long. Each premaxilla (the bones that formed the tip of the snout) held five teeth with D-shaped cross-sections, and each maxilla (the main tooth-bearing bones in the upper jaw) had between 14 and 17 teeth; the number of teeth does not exactly correspond to the size of the bone. Each dentary (the tooth-bearing bone of

6536-479: A species (or replacement by a daughter species) plays a key role in the punctuated equilibrium hypothesis of Stephen Jay Gould and Niles Eldredge . In ecology , extinction is sometimes used informally to refer to local extinction , in which a species ceases to exist in the chosen area of study, despite still existing elsewhere. Local extinctions may be made good by the reintroduction of individuals of that species taken from other locations; wolf reintroduction

6708-439: A species may come suddenly when an otherwise healthy species is wiped out completely, as when toxic pollution renders its entire habitat unliveable; or may occur gradually over thousands or millions of years, such as when a species gradually loses out in competition for food to better adapted competitors. Extinction may occur a long time after the events that set it in motion, a phenomenon known as extinction debt . Assessing

6880-481: A species of Allosaurus was found at Cape Paterson, Victoria in Early Cretaceous beds in southeastern Australia. It was thought to provide evidence that Australia was a refugium for animals that had gone extinct elsewhere. This identification was challenged by Samuel Welles , who thought it more resembled that of an ornithomimid , but the original authors defended their identification. With fifteen years of new specimens and research to look at, Daniel Chure reexamined

7052-404: A species or group of species. "Just as each species is unique", write Beverly and Stephen C. Stearns , "so is each extinction ... the causes for each are varied—some subtle and complex, others obvious and simple". Most simply, any species that cannot survive and reproduce in its environment and cannot move to a new environment where it can do so, dies out and becomes extinct. Extinction of

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7224-532: A specimen in the Como Bluff area of Wyoming in 1879 , but apparently did not mention its completeness and Cope never unpacked it. Upon unpacking it in 1903 (several years after Cope had died), it was found to be one of the most complete theropod specimens then known and the skeleton, now cataloged as AMNH 5753, was put on public view in 1908 . This is the well-known mount poised over a partial Apatosaurus skeleton as if scavenging it, illustrated as such in

7396-518: A subsequent report, IPBES listed unsustainable fishing, hunting and logging as being some of the primary drivers of the global extinction crisis. In June 2019, one million species of plants and animals were at risk of extinction. At least 571 plant species have been lost since 1750, but likely many more. The main cause of the extinctions is the destruction of natural habitats by human activities, such as cutting down forests and converting land into fields for farming. A dagger symbol (†) placed next to

7568-461: 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 . Allosaurus itself is based on YPM 1930, a small collection of fragmentary bones including parts of three vertebrae, a rib fragment, a tooth, a toe bone, and (most useful for later discussions)

7740-482: A teaching position at Yale upon his return. From the 1870s to 1890s, he competed with rival paleontologist Edward Drinker Cope in a period of frenzied Western American expeditions known as the Bone Wars . Marsh's greatest legacy is the collection of Mesozoic reptiles, Cretaceous birds, and Mesozoic and Tertiary mammals that now constitute the backbone of the collections of Yale's Peabody Museum of Natural History and

7912-634: A very complicated taxonomy and includes at least three valid species , the best known of which is A. fragilis . The bulk of Allosaurus remains have come from North America's Morrison Formation , with material also known from the Lourinhã Formation in Portugal. It was known for over half of the 20th century as Antrodemus , but a study of the abundant remains from the Cleveland-Lloyd Dinosaur Quarry returned

8084-491: Is Labrosaurus ferox , named in 1884 by Marsh for an oddly formed partial lower jaw, with a prominent gap in the tooth row at the tip of the jaw, and a rear section greatly expanded and turned down. Later researchers suggested that the bone was pathologic , showing an injury to the living animal, and that part of the unusual form of the rear of the bone was due to plaster reconstruction. It is now regarded as an example of A. fragilis . In his 1988 book, Predatory Dinosaurs of

8256-464: Is a separate species at minimum. A. maximus was a new combination by David K. Smith for Chure's Saurophaganax maximus , a taxon created by Chure in 1995 for giant allosaurid remains from the Morrison of Oklahoma. These remains had been known as Saurophagus , but that name was already in use, leading Chure to propose a substitute. Smith, in his 1998 analysis of variation, concluded that S. maximus

8428-476: Is a typographical error for A. fragilis. "Allosaurus ferox" is a typographical error by Marsh for A. fragilis in a figure caption for the partial skull YPM 1893 and YPM 1893 has been treated as a specimen of A fragilis . Likewise, "Labrosaurus fragilis" is a typographical error by Marsh ( 1896 ) for Labrosaurus ferox . "A. whitei" is a nomen nudum coined by Pickering in 1996 for the complete Allosaurus specimens that Paul referred to A. atrox . "Madsenius"

8600-523: Is also evidence to suggest that this event was preceded by another mass extinction, known as Olson's Extinction . The Cretaceous–Paleogene extinction event (K–Pg) occurred 66 million years ago, at the end of the Cretaceous period; it is best known for having wiped out non-avian dinosaurs , among many other species. According to a 1998 survey of 400 biologists conducted by New York 's American Museum of Natural History , nearly 70% believed that

8772-444: Is an example of this. Species that are not globally extinct are termed extant . Those species that are extant, yet are threatened with extinction, are referred to as threatened or endangered species . Currently, an important aspect of extinction is human attempts to preserve critically endangered species. These are reflected by the creation of the conservation status "extinct in the wild" (EW) . Species listed under this status by

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8944-585: Is difficult to demonstrate unless one has a strong chain of evidence linking a living species to members of a pre-existing species. For example, it is sometimes claimed that the extinct Hyracotherium , which was an early horse that shares a common ancestor with the modern horse , is pseudoextinct, rather than extinct, because there are several extant species of Equus , including zebra and donkey ; however, as fossil species typically leave no genetic material behind, one cannot say whether Hyracotherium evolved into more modern horse species or merely evolved from

9116-417: Is estimated as 100 to 1,000 times "background" rates (the average extinction rates in the evolutionary time scale of planet Earth), faster than at any other time in human history, while future rates are likely 10,000 times higher. However, some groups are going extinct much faster. Biologists Paul R. Ehrlich and Stuart Pimm , among others, contend that human population growth and overconsumption are

9288-504: Is no longer the case at the species level. A. jimmadseni has been scientifically described based on two nearly complete skeletons. The first specimen to wear the identification was unearthed in Dinosaur National Monument in northeastern Utah, with the original "Big Al" individual subsequently recognized as belonging to the same species. This species differs from A. fragilis in several anatomical details, including

9460-609: Is now regarded as a dubious Ceratosaurus -like ceratosaur. A. tendagurensis was named in 1925 by Werner Janensch for a partial shin (MB.R.3620) found in the Kimmeridgian-age Tendaguru Formation in Mtwara , Tanzania. Although tabulated as a tentatively valid species of Allosaurus in the second edition of the Dinosauria, subsequent studies place it as indeterminate beyond Tetanurae, either

9632-455: Is now regarded as a dubious theropod. Labrosaurus stechowi , described in 1920 by Janensch based on isolated Ceratosaurus -like teeth from the Tendaguru beds of Tanzania, was listed by Donald F. Glut as a species of Allosaurus , is now considered a dubious ceratosaurian related to Ceratosaurus . L. sulcatus , named by Marsh in 1896 for a Morrison theropod tooth, which like L. stechowi

9804-440: Is reasonable for large adults of A. fragilis , but that 700 kg (1,500 lb) is a closer estimate for individuals represented by the average-sized thigh bones he has measured. Using the subadult specimen nicknamed "Big Al", since assigned to the species Allosaurus jimmadseni , researchers using computer modeling arrived at a best estimate of 1.5 t (1.7 short tons) for the individual, but by varying parameters they found

9976-593: Is regarded as the most common, known from the remains of at least 60 individuals. For a while in the late 1980s and early 1990s, it was common to recognize A. fragilis as the short-snouted species, with the long-snouted taxon being A. atrox. However, subsequent analysis of specimens from the Cleveland-Lloyd Dinosaur Quarry, Como Bluff, and Dry Mesa Quarry showed that the differences seen in the Morrison Formation material could be attributed to individual variation. A study of skull elements from

10148-592: Is the destruction of ocean floors by bottom trawling . Diminished resources or introduction of new competitor species also often accompany habitat degradation. Global warming has allowed some species to expand their range, bringing competition to other species that previously occupied that area. Sometimes these new competitors are predators and directly affect prey species, while at other times they may merely outcompete vulnerable species for limited resources. Vital resources including water and food can also be limited during habitat degradation, leading to extinction. In

10320-525: Is the most important determinant of genus extinction at background rates but becomes increasingly irrelevant as mass extinction arises. Limited geographic range is a cause both of small population size and of greater vulnerability to local environmental catastrophes. Extinction rates can be affected not just by population size, but by any factor that affects evolvability , including balancing selection , cryptic genetic variation , phenotypic plasticity , and robustness . A diverse or deep gene pool gives

10492-457: Is the termination of a taxon by the death of its last member . A taxon may become functionally extinct before the death of its last member if it loses the capacity to reproduce and recover. Because a species' potential range may be very large, determining this moment is difficult, and is usually done retrospectively. This difficulty leads to phenomena such as Lazarus taxa , where a species presumed extinct abruptly "reappears" (typically in

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10664-489: The American Civil War , although he might have also been disqualified from service on account of his eyesight. Marsh traveled through England, France, Germany, and Switzerland, studying with or making the acquaintance of prominent scientists such as Heinrich Ernst Beyrich , Wilhelm Peters , Christian Gottfried Ehrenberg and Henry Woodward . In discussions with his uncle, Marsh convinced the businessman to fund

10836-447: The Cleveland-Lloyd Dinosaur Quarry (Utah) specimens are generally smaller than those from Como Bluff (Wyoming) or Brigham Young University 's Dry Mesa Quarry (Colorado), but the shapes of the bones themselves did not vary between the sites. A later study by Smith incorporating Garden Park (Colorado) and Dinosaur National Monument (Utah) specimens found no justification for multiple species based on skeletal variation; skull variation

11008-499: The Cleveland-Lloyd Dinosaur Quarry in Emery County , Utah, had taken place as early as 1927 and the fossil site itself described by William L. Stokes in 1945 , major operations did not begin there until 1960 . Under a cooperative effort involving nearly 40 institutions, thousands of bones were recovered between 1960 and 1965 , led by James Henry Madsen. The quarry is notable for the predominance of Allosaurus remains,

11180-483: The International Union for Conservation of Nature (IUCN) are not known to have any living specimens in the wild and are maintained only in zoos or other artificial environments. Some of these species are functionally extinct, as they are no longer part of their natural habitat and it is unlikely the species will ever be restored to the wild. When possible, modern zoological institutions try to maintain

11352-485: The Late Pleistocene could take up to 5 to 7 million years to restore mammal diversity to what it was before the human era. Extinction of a parent species where daughter species or subspecies are still extant is called pseudoextinction or phyletic extinction. Effectively, the old taxon vanishes, transformed ( anagenesis ) into a successor, or split into more than one ( cladogenesis ). Pseudoextinction

11524-503: The Smithsonian Institution . Marsh has been called "both a superb paleontologist and the greatest proponent of Darwinism in nineteenth-century America." Othniel Charles Marsh was born on October 29, 1831, near Lockport, New York. He was the third of four children born to Mary Gaines Peabody (1807–1834) and Caleb Marsh (1800–1865). The Marsh (nee Marshe) family and Peabody families immigrated to America from England in

11696-616: The fossil record ) after a period of apparent absence. More than 99% of all species that ever lived on Earth , amounting to over five billion species, are estimated to have died out. It is estimated that there are currently around 8.7 million species of eukaryotes globally, and possibly many times more if microorganisms , like bacteria , are included. Notable extinct animal species include non-avian dinosaurs , saber-toothed cats , dodos , mammoths , ground sloths , thylacines , trilobites , golden toads , and passenger pigeons . Through evolution , species arise through

11868-402: The mandible , showing scales measuring 1–2 mm in diameter. The same fossil also preserves skin impressions from the ventral side of the neck, showing broad scutes . A small skin impression from an Allosaurus skull has been reported but never described. Allosaurus was an allosaurid, a member of a family of large theropods within the larger group Carnosauria . The family name Allosauridae

12040-437: The sense of smell , perhaps holding something like Jacobson's organs . The roof of the braincase was thin, perhaps to improve thermoregulation for the brain. The skull and lower jaws had joints that permitted motion within these units. In the lower jaws, the bones of the front and back halves loosely articulated, permitting the jaws to bow outward and increasing the animal's gape. The braincase and frontals may also have had

12212-410: The slender-billed curlew ( Numenius tenuirostris ), not seen since 2007. As long as species have been evolving, species have been going extinct. It is estimated that over 99.9% of all species that ever lived are extinct. The average lifespan of a species is 1–10 million years, although this varies widely between taxa. A variety of causes can contribute directly or indirectly to the extinction of

12384-571: The state fossil of Utah in 1988 . The period since Madsen's monograph has been marked by a great expansion in studies dealing with topics concerning Allosaurus in life ( paleobiological and paleoecological topics). Such studies have covered topics including skeletal variation, growth, skull construction, hunting methods, the brain, and the possibility of gregarious living and parental care. Reanalysis of old material (particularly of large 'allosaur' specimens), new discoveries in Portugal, and several very complete new specimens have also contributed to

12556-488: The strata of the Paris basin. They saw alternating saltwater and freshwater deposits, as well as patterns of the appearance and disappearance of fossils throughout the record. From these patterns, Cuvier inferred historic cycles of catastrophic flooding, extinction, and repopulation of the earth with new species. Cuvier's fossil evidence showed that very different life forms existed in the past than those that exist today,

12728-471: The taphonomy of the site, suggesting numerous mutually exclusive explanations for how it may have formed. Suggestions have ranged from animals getting stuck in a bog, becoming trapped in deep mud, falling victim to drought-induced mortality around a waterhole, and getting trapped in a spring-fed pond or seep. Regardless of the actual cause, the great quantity of well-preserved Allosaurus remains has allowed this genus to be known in great detail, making it among

12900-465: The type species A. fragilis , A. jimmadseni and A. lucasi . Among these, Daniel Chure and Mark Loewen in 2020 only recognized the species A. fragilis , A. europaeus , and the newly-named A. jimmadseni as being valid species. However, A. europaeus does not show any unique characters compared to the North American species, so a reevaluation of its validity is required. A. fragilis is

13072-467: The 1630s. Mary died shortly after the birth of her fourth child in 1834. Caleb remarried in 1836 and Othniel moved with the family to Bradford, Massachusetts . Soon after, Caleb's business fortunes soured, and Othniel's early years were marked by financial struggles. Caleb purchased a farm in Lockport when Marsh was twelve. As the eldest son, Othniel was expected to assist his father on the farm, and

13244-639: The 20 biodiversity goals laid out by the Aichi Biodiversity Targets in 2010, only 6 were "partially achieved" by the deadline of 2020. The report warned that biodiversity will continue to decline if the status quo is not changed, in particular the "currently unsustainable patterns of production and consumption, population growth and technological developments". In a 2021 report published in the journal Frontiers in Conservation Science , some top scientists asserted that even if

13416-451: The Aichi Biodiversity Targets set for 2020 had been achieved, it would not have resulted in a significant mitigation of biodiversity loss. They added that failure of the global community to reach these targets is hardly surprising given that biodiversity loss is "nowhere close to the top of any country's priorities, trailing far behind other concerns such as employment, healthcare, economic growth, or currency stability." For much of history,

13588-600: The Cleveland-Lloyd site found wide variation between individuals, calling into question previous species-level distinctions based on such features as the shape of the lacrimal horns and the proposed differentiation of A. jimmadseni based on the shape of the jugal . A. europaeus was found in the Kimmeridgian-age Porto Novo Member of the Lourinhã Formation , but it may be the same as A. fragilis . Allosaurus material from Portugal

13760-487: The Cleveland-Lloyd specimens and concluded that Allosaurus 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. " Antrodemus " has been used informally for convenience when distinguishing between the skull Gilmore restored and the composite skull restored by Madsen. Although sporadic work at what became known as

13932-618: The Earth is currently in the early stages of a human-caused mass extinction, known as the Holocene extinction . In that survey, the same proportion of respondents agreed with the prediction that up to 20% of all living populations could become extinct within 30 years (by 2028). A 2014 special edition of Science declared there is widespread consensus on the issue of human-driven mass species extinctions. A 2020 study published in PNAS stated that

14104-468: The Jurassic than A. fragilis and differs from other species of Allosaurus in cranial details. However, more material may show it to be A. fragilis , as originally described. The issue of species and potential synonyms is complicated by the type specimen of Allosaurus fragilis ( YPM  1930) being extremely fragmentary, consisting of a few incomplete vertebrae, limb fragments, rib fragments, and

14276-530: The Law of brain growth, which states that, during the tertiary period, many taxonomic groups presented gradual increase in the size of the brain. This evolutionary law remains being used due to its explanatory, and to a certain extent, predictive potential Prior to Marsh's efforts, the entirety of fossil remains known in North America was quite small. As a result of the generosity of George Peabody , Marsh

14448-520: The North American moose and that the animal had once been common on the British Isles . Rather than suggest that this indicated the possibility of species going extinct, he argued that although organisms could become locally extinct, they could never be entirely lost and would continue to exist in some unknown region of the globe. The antlers were later confirmed to be from the extinct deer Megaloceros . Hooke and Molyneux's line of thinking

14620-522: The Paris basin, could be formed by a slow rise and fall of sea levels . The concept of extinction was integral to Charles Darwin 's On the Origin of Species , with less fit lineages disappearing over time. For Darwin, extinction was a constant side effect of competition . Because of the wide reach of On the Origin of Species , it was widely accepted that extinction occurred gradually and evenly (a concept now referred to as background extinction ). It

14792-906: The Peabody fossil hall. He donated his home in New Haven, Connecticut, to Yale University in 1899. The Othniel C. Marsh House , now known as Marsh Hall, is designated a National Historic Landmark . Marsh Hall serves as the home of the Yale School of Forestry at the Yale School of the Environment . The grounds are now known as the Marsh Botanical Garden . Marsh was elected a member of the American Antiquarian Society in 1877. Marsh formulated

14964-649: The USGS, and Marsh's contacts in Washington, Marsh was placed at the head of the consolidated government survey in the late 1880s. In 1880, Marsh caught the attention of the scientific world with the publication of Odontornithes: a Monograph on Extinct Birds of North America, which included his discoveries of birds with teeth. These skeletons helped bridge the gap between dinosaurs and birds, and provided invaluable support for Darwin's theory of evolution. Darwin wrote to Marsh saying, "Your work on these old birds & on

15136-410: The United States government, to force the removal of Native Americans , many of whom relied on the bison for food. Othniel Charles Marsh Born into a modest family, Marsh was able to afford higher education thanks to the generosity of his wealthy uncle George Peabody . After graduating from Yale College in 1860 he travelled the world, studying anatomy , mineralogy and geology . He obtained

15308-464: The World , the freelance artist & author Gregory S. Paul proposed that A. fragilis had tall pointed horns and a slender build compared to a postulated second species A. atrox , as well as not being a different sex due to rarity. Allosaurus atrox was originally named by Marsh in 1878 as the type species of its own genus, Creosaurus , and is based on YPM 1890, an assortment of bones that includes

15480-429: The accumulation of slightly deleterious mutations , then a population will go extinct. Smaller populations have fewer beneficial mutations entering the population each generation, slowing adaptation. It is also easier for slightly deleterious mutations to fix in small populations; the resulting positive feedback loop between small population size and low fitness can cause mutational meltdown . Limited geographic range

15652-419: The advent of cladistic study of evolutionary relationships, none of these theropods is now recognized as an allosaurid, although several, like Acrocanthosaurus and Yangchuanosaurus , are members of closely related families. Below is a cladogram based on the analysis of Benson et al. in 2010. Sinraptoridae Allosaurus [REDACTED] Neovenator [REDACTED] Extinct Extinction

15824-467: The aquatic reptile Elasmosaurus , was flawed: Cope had placed the head of the animal where its tail should have been. Marsh's criticism wrankled Cope, and threatened his nascent career; he responded by critiquing errors in Marsh's work, and moving in on areas Marsh was prospecting in. Their relationship began to sour. Marsh was looking further afield than New Jersey for fossils. After visiting Chicago for

15996-414: The base of the tail, measures 20 cm x 20 cm and shows large scales measuring up to 2 cm in diameter. However, it has been noted that these scales are more similar to those of sauropods , and due to the presence of non-theropod remains associated with the tail of "Big Al Two" there is a possibility that this skin impression is not from Allosaurus . Another Allosaurus fossil features a skin impression from

16168-401: The best-known of all theropods. Skeletal remains from the quarry pertain to individuals of almost all ages and sizes, from less than 1 metre (3.3 feet) to 12 metres (39 feet) long, and the disarticulation is an advantage for describing bones usually found fused. Due to being one of Utah's two fossil quarries where numerous Allosaurus specimens have been discovered, Allosaurus was designated as

16340-412: The birds), are interpreted as having held air sacs used in respiration . The rib cage was broad, giving it a barrel chest, especially in comparison to less derived theropods like Ceratosaurus . Allosaurus had gastralia (belly ribs), but these are not common findings, and they may have ossified poorly. In one published case, the gastralia show evidence of injury during life. A furcula (wishbone)

16512-463: The bone and found that it was not Allosaurus , but could represent an allosauroid. Similarly, Yoichi Azuma and Phil Currie , in their description of Fukuiraptor , noted that the bone closely resembled that of their new genus. This specimen is sometimes referred to as " Allosaurus robustus ", an informal museum name. It likely belonged to something similar to Australovenator , although one study considered it to belong to an abelisaur . Allosaurus

16684-411: The condition of the specimens, and the lack of scientific resolution on how it came to be. The majority of bones belong to the large theropod Allosaurus fragilis (it is estimated that the remains of at least 46  A. fragilis have been found there, out of at a minimum 73 dinosaurs) and the fossils found there are disarticulated and well-mixed. Nearly a dozen scientific papers have been written on

16856-600: The consequences can be catastrophic. Invasive alien species can affect native species directly by eating them, competing with them, and introducing pathogens or parasites that sicken or kill them; or indirectly by destroying or degrading their habitat. Human populations may themselves act as invasive predators. According to the "overkill hypothesis", the swift extinction of the megafauna in areas such as Australia (40,000 years before present), North and South America (12,000 years before present), Madagascar , Hawaii (AD 300–1000), and New Zealand (AD 1300–1500), resulted from

17028-418: The contemporary extinction crisis "may be the most serious environmental threat to the persistence of civilization, because it is irreversible." Biologist E. O. Wilson estimated in 2002 that if current rates of human destruction of the biosphere continue, one-half of all plant and animal species of life on earth will be extinct in 100 years. More significantly, the current rate of global species extinctions

17200-415: The convoluted situation was produced by Charles W. Gilmore in 1920 . He 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 50 years, until James Henry Madsen published on

17372-599: The country, visiting museums to inform the planning of the Yale Museum. In 1868, he visited Cope; since their meeting, they had expressed warm wishes in letters to each other and even named species after each other. Cope took Marsh on a tour of the marl pits in New Jersey where he was finding fossils; unbeknownst to Cope, Marsh would later pay the pit operators to divert their finds to him instead of Cope. Marsh later noted that Cope's reconstruction of his newest find,

17544-476: The deliberate destruction of some species, such as dangerous viruses , and the total destruction of other problematic species has been suggested. Other species were deliberately driven to extinction, or nearly so, due to poaching or because they were "undesirable", or to push for other human agendas. One example was the near extinction of the American bison , which was nearly wiped out by mass hunts sanctioned by

17716-403: The endangered wild water buffalo is most threatened with extinction by genetic pollution from the abundant domestic water buffalo ). Such extinctions are not always apparent from morphological (non-genetic) observations. Some degree of gene flow is a normal evolutionary process; nevertheless, hybridization (with or without introgression) threatens rare species' existence. The gene pool of

17888-591: The event of rediscovery would be considered Lazarus species. Examples include the thylacine , or Tasmanian tiger ( Thylacinus cynocephalus ), the last known example of which died in Hobart Zoo in Tasmania in 1936; the Japanese wolf ( Canis lupus hodophilax ), last sighted over 100 years ago; the American ivory-billed woodpecker ( Campephilus principalis ), with the last universally accepted sighting in 1944; and

18060-443: The extinction crisis. According to the International Union for Conservation of Nature (IUCN), 784 extinctions have been recorded since the year 1500, the arbitrary date selected to define "recent" extinctions, up to the year 2004; with many more likely to have gone unnoticed. Several species have also been listed as extinct since 2004. If adaptation increasing population fitness is slower than environmental degradation plus

18232-475: The extinction of species caused by humanity, and they try to prevent further extinctions through a variety of conservation programs. Humans can cause extinction of a species through overharvesting , pollution , habitat destruction , introduction of invasive species (such as new predators and food competitors ), overhunting, and other influences. Explosive, unsustainable human population growth and increasing per capita consumption are essential drivers of

18404-427: The eyes. These horns were composed of extensions of the lacrimal bones , and varied in shape and size. There were also lower paired ridges running along the top edges of the nasal bones that led into the horns. The horns were probably covered in a keratin sheath and may have had a variety of functions, including acting as sunshades for the eyes, being used for display, and being used in combat against other members of

18576-540: The field of zoology , and biology in general, and has also become an area of concern outside the scientific community. A number of organizations, such as the Worldwide Fund for Nature , have been created with the goal of preserving species from extinction. Governments have attempted, through enacting laws, to avoid habitat destruction, agricultural over-harvesting, and pollution . While many human-caused extinctions have been accidental, humans have also engaged in

18748-408: The forearm was somewhat shorter than the upper arm (1:1.2 ulna / humerus ratio). The wrist had a version of the semilunate carpal also found in more derived theropods like maniraptorans . Of the three fingers, the innermost (or thumb) was the largest, and diverged from the others. The phalangeal formula is 2-3-4-0-0, meaning that the innermost finger (phalange) has two bones, the next has three, and

18920-435: The form of a physical destruction of niche habitats. The widespread destruction of tropical rainforests and replacement with open pastureland is widely cited as an example of this; elimination of the dense forest eliminated the infrastructure needed by many species to survive. For example, a fern that depends on dense shade for protection from direct sunlight can no longer survive without forest to shelter it. Another example

19092-564: The genus Allosaurus as Allosaurus maximus , though recent studies support it as a separate genus. Another potential specimen of Allosaurus , once assigned to the genus Epanterias (AMNH 5767), may have measured 12.1 m (40 ft) in length. A more recent discovery is a partial skeleton from the Peterson Quarry in Morrison rocks of New Mexico ; this large allosaurid may be another individual of Saurophaganax . David K. Smith, examining Allosaurus fossils by quarry, found that

19264-514: The genus. A. medius was named by Marsh in 1888 for various specimens from the Early Cretaceous Arundel Formation of Maryland , although most of the remains were removed by Richard Swann Lull to the new ornithopod species Dryosaurus grandis , except for a tooth. It was transferred to Antrodemus by Oliver Hay in 1902, but Hay later clarified that this was an inexplicable error on his part. Gilmore considered

19436-481: The growing knowledge base. In 1991 , "Big Al" ( MOR 693), a 95% complete, partially articulated specimen of Allosaurus was discovered, measuring about 8 metres (26 ft) long. MOR 693 was excavated near Shell, Wyoming , by a joint Museum of the Rockies and University of Wyoming Geological Museum team. This skeleton was discovered by a Swiss team, led by Kirby Siber. Chure and Loewen in 2020 identified

19608-580: The habitat retreat of taxa approaching extinction. Possible causes of the higher extinction risk in species with more sexual selection shown by the comprehensive fossil studies that rule out such error sources include expensive sexually selected ornaments having negative effects on the ability to survive natural selection , as well as sexual selection removing a diversity of genes that under current ecological conditions are neutral for natural selection but some of which may be important for surviving climate change. There have been at least five mass extinctions in

19780-676: The heaviest losses include the Cape Floristic Region and the Caribbean Basin . These areas might see a doubling of present carbon dioxide levels and rising temperatures that could eliminate 56,000 plant and 3,700 animal species. Climate change has also been found to be a factor in habitat loss and desertification . Studies of fossils following species from the time they evolved to their extinction show that species with high sexual dimorphism , especially characteristics in males that are used to compete for mating, are at

19952-447: The history of life on earth, and four in the last 350 million years in which many species have disappeared in a relatively short period of geological time. A massive eruptive event that released large quantities of tephra particles into the atmosphere is considered to be one likely cause of the " Permian–Triassic extinction event " about 250 million years ago, which is estimated to have killed 90% of species then existing. There

20124-475: The human era since the Late Pleistocene would require 5 to 7 million years to recover. According to the 2019 Global Assessment Report on Biodiversity and Ecosystem Services by IPBES , the biomass of wild mammals has fallen by 82%, natural ecosystems have lost about half their area and a million species are at risk of extinction—all largely as a result of human actions. Twenty-five percent of plant and animal species are threatened with extinction. In

20296-438: The individual as a representative of the species Allosaurus jimmadseni . In 1996 , the same team discovered a second Allosaurus , "Big Al II". This specimen, the best preserved skeleton of its kind to date, is also referred to Allosaurus jimmadseni . The completeness, preservation, and scientific importance of this skeleton gave "Big Al" its name. The individual itself was below the average size for Allosaurus fragilis , as it

20468-431: The introduced ( or hybrid ) species. Endemic populations can face such extinctions when new populations are imported or selectively bred by people, or when habitat modification brings previously isolated species into contact. Extinction is likeliest for rare species coming into contact with more abundant ones; interbreeding can swamp the rarer gene pool and create hybrids, depleting the purebred gene pool (for example,

20640-720: The large and powerful legs, its three-fingered hands were small and the body was balanced by a long, muscular tail. It is classified as an allosaurid , a type of carnosaurian theropod dinosaur. As the most abundant large predator of the Morrison Formation, Allosaurus was at the top of the food chain and probably preyed on contemporaneous large herbivorous dinosaurs, with the possibility of hunting other predators. Potential prey included ornithopods , stegosaurids , and sauropods . Some paleontologists interpret Allosaurus as having had cooperative social behavior and hunting in packs, while others believe individuals may have been aggressive toward each other and that congregations of this genus are

20812-476: The living animal was infection and trauma to the right foot that probably affected movement and may have also predisposed the other foot to injury because of a change in gait. "Big Al" had an infection on the first phalanx on the third toe that was afflicted by an involucrum . The infection was long-lived, perhaps up to six months. "Big Al II" is also known to have multiple injuries. Six species of Allosaurus have been named: A. amplus , A. atrox , A. europaeus ,

20984-410: The lower jaw) had between 14 and 17 teeth, with an average count of 16. The teeth became shorter, narrower, and more curved toward the back of the skull. All of the teeth had saw-like edges. They were shed easily, and were replaced continually, making them common fossils. Its skull was light, robust and equipped with dozens of sharp, serrated teeth. The skull had a pair of horns above and in front of

21156-488: The main drivers of the modern extinction crisis. In January 2020, the UN's Convention on Biological Diversity drafted a plan to mitigate the contemporary extinction crisis by establishing a deadline of 2030 to protect 30% of the Earth's land and oceans and reduce pollution by 50%, with the goal of allowing for the restoration of ecosystems by 2050. The 2020 United Nations ' Global Biodiversity Outlook report stated that of

21328-550: The many fossil animals of N. America has afforded the best support to the theory of evolution, which has appeared within the last 20 years" (since Darwin's publication of Origin of Species). Between 1883 and 1895, Marsh was President of the National Academy of Sciences . The pinnacle of Marsh's work with dinosaurs came in 1896 with the publication of his two quartos, Dinosaurs of North America and Vertebrate Fossils, which demonstrated his unsurpassed knowledge of

21500-421: The modern understanding of extinction as the end of a species was incompatible with the prevailing worldview. Prior to the 19th century, much of Western society adhered to the belief that the world was created by God and as such was complete and perfect. This concept reached its heyday in the 1700s with the peak popularity of a theological concept called the great chain of being , in which all life on earth, from

21672-452: The name " Allosaurus " to prominence. As one of the first well-known theropod dinosaurs, it has long attracted attention outside of paleontological circles. Allosaurus was a large bipedal predator for its time. Its skull was light, robust, and equipped with dozens of sharp, serrated teeth. It averaged 8.5 metres (28 ft) in length for A. fragilis , with the largest specimens estimated as being 9.7 metres (32 ft) long. Relative to

21844-755: The name "Megalosauridae" instead of "Allosauridae" include Gilmore , 1920, von Huene , 1926, Romer , 1956 and 1966, Steel, 1970, and Walker , 1964. Following the publication of Madsen's influential monograph, Allosauridae became the preferred family assignment, but it too was not strongly defined. Semi-technical works used Allosauridae for a variety of large theropods, usually those that were larger and better-known than megalosaurids. Typical theropods that were thought to be related to Allosaurus included Indosaurus , Piatnitzkysaurus , Piveteausaurus , Yangchuanosaurus , Acrocanthosaurus , Chilantaisaurus , Compsosuchus , Stokesosaurus , and Szechuanosaurus . Given modern knowledge of theropod diversity and

22016-490: The name of a species or other taxon normally indicates its status as extinct. Examples of species and subspecies that are extinct include: A species is extinct when the last existing member dies. Extinction therefore becomes a certainty when there are no surviving individuals that can reproduce and create a new generation. A species may become functionally extinct when only a handful of individuals survive, which cannot reproduce due to poor health, age, sparse distribution over

22188-469: The natural course of events, species become extinct for a number of reasons, including but not limited to: extinction of a necessary host, prey or pollinator, interspecific competition , inability to deal with evolving diseases and changing environmental conditions (particularly sudden changes) which can act to introduce novel predators, or to remove prey. Recently in geological time, humans have become an additional cause of extinction of some species, either as

22360-410: The newly emerging school of uniformitarianism . Jean-Baptiste Lamarck , a gradualist and colleague of Cuvier, saw the fossils of different life forms as evidence of the mutable character of species. While Lamarck did not deny the possibility of extinction, he believed that it was exceptional and rare and that most of the change in species over time was due to gradual change. Unlike Cuvier, Lamarck

22532-501: The original core of the collection of Yale's Peabody Museum of Natural History . The museum's Great Hall is dominated by the first fossil skeleton of Brontosaurus that he discovered, which was reclassified as Apatosaurus for a time. However, an extensive study published in 2015 concluded that Brontosaurus was a valid genus of sauropod distinct from Apatosaurus . Some other Marsh taxa like Camarasaurus lentus , Nanosaurus agilis , and Camptosaurus dispar are also represented in

22704-399: The original population, thereby increasing the chance of extinction. Habitat degradation is currently the main anthropogenic cause of species extinctions. The main cause of habitat degradation worldwide is agriculture, with urban sprawl , logging, mining, and some fishing practices close behind. The degradation of a species' habitat may alter the fitness landscape to such an extent that

22876-472: The other students, he was nicknamed "Daddy" by his peers. He was initially an unremarkable student, devoting much of his time to leisure and games, but the next year decided to focus on his studies. "I changed my mind," he later told a biographer, "during an afternoon spent on Dracut Heights [Lowell]. I resolved that I would return to Andover, take hold, and really study." Marsh applied himself to his studies and graduated valedictorian of his class in 1856. In

23048-702: The process of speciation —where new varieties of organisms arise and thrive when they are able to find and exploit an ecological niche —and species become extinct when they are no longer able to survive in changing conditions or against superior competition . The relationship between animals and their ecological niches has been firmly established. A typical species becomes extinct within 10 million years of its first appearance, although some species, called living fossils , survive with little to no morphological change for hundreds of millions of years. Mass extinctions are relatively rare events; however, isolated extinctions of species and clades are quite common, and are

23220-476: The pubes had not fused to each other at their foot ends. He suggested that this was a sexual characteristic , with females lacking fused bones to make egg-laying easier. This proposal has not attracted further attention, however. The forelimbs of Allosaurus were short in comparison to the hindlimbs (only about 35% the length of the hindlimbs in adults) and had three fingers per hand, tipped with large, strongly curved and pointed claws . The arms were powerful, and

23392-410: The relative importance of genetic factors compared to environmental ones as the causes of extinction has been compared to the debate on nature and nurture . The question of whether more extinctions in the fossil record have been caused by evolution or by competition or by predation or by disease or by catastrophe is a subject of discussion; Mark Newman, the author of Modeling Extinction , argues for

23564-561: The result of lone individuals feeding on the same carcasses. The discovery and early study of Allosaurus is complicated by the multiplicity of names coined during the Bone Wars of the late 19th century. The first described fossil in this history was a bone obtained secondhand by Ferdinand Vandeveer 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 hoofs". Hayden sent his specimen to Joseph Leidy , who identified it as half of

23736-430: The same species (although they were fragile). There was a ridge along the back of the skull roof for muscle attachment, as is also seen in tyrannosaurids . Inside the lacrimal bones were depressions that may have held glands , such as salt glands . Within the maxillae were sinuses that were better developed than those of more basal theropods such as Ceratosaurus and Marshosaurus ; they may have been related to

23908-400: The shaft of the right humerus (upper arm). Othniel Charles Marsh gave these remains the formal name Allosaurus fragilis in 1877. Allosaurus comes from the Greek words allos / αλλος , meaning "strange" or "different", and sauros / σαυρος , meaning "lizard" or "reptile". It was named 'different lizard' because its vertebrae were different from those of other dinosaurs known at

24080-437: The shape of the horns, and the proposed differentiation of A. jimmadseni based on the shape of the jugal . A study published by Motani et al., in 2020 suggests that Allosaurus was also sexually dimorphic in the width of the femur's head against its length. The skull and teeth of Allosaurus were modestly proportioned for a theropod of its size. Paleontologist Gregory S. Paul gives a length of 845 mm (33.3 in) for

24252-460: The species is no longer able to survive and becomes extinct. This may occur by direct effects, such as the environment becoming toxic , or indirectly, by limiting a species' ability to compete effectively for diminished resources or against new competitor species. Habitat destruction, particularly the removal of vegetation that stabilizes soil, enhances erosion and diminishes nutrient availability in terrestrial ecosystems. This degradation can lead to

24424-602: The subject. On December 13, 1897, Marsh received the Cuvier Prize of 1,500 francs from the French Academy of Science . According to Peter Dodson , Cope and Marsh "[have] left a legacy, and each was a distinguished researcher. But really it seems impossible to say one name without the other. Cope and Marsh." Marsh's names for three dinosaur groups, and nineteen genera, have survived, and though only three of Cope's named genera are still in use, he published

24596-430: The sudden introduction of human beings to environments full of animals that had never seen them before and were therefore completely unadapted to their predation techniques. Coextinction refers to the loss of a species due to the extinction of another; for example, the extinction of parasitic insects following the loss of their hosts. Coextinction can also occur when a species loses its pollinator , or to predators in

24768-597: The summers off of school, he prospected for minerals in New York, Massachusetts, and Nova Scotia. Upon gradation, Marsh decided to attend Yale, rather than Harvard, where many of his relatives had attended. He ran his letter to George Peabody asking for the funds by Aunt Judith first, who disapprovingly noted it contained two spelling errors. Peabody agreed to cover Marsh's expenses and give him an allowance for spending money, and Marsh moved to New Haven in September. Marsh

24940-496: The synonymy of Apatodon with Allosaurus was due to correspondence to Ralph Molnar by John McIntosh, whereby the latter reportedly found a paper saying that Othniel Charles Marsh admitted that the Apatodon holotype was actually an allosaurid dorsal vertebra. A. amplexus was named by Gregory S. Paul for giant Morrison allosaur remains, and included in his conception Saurophagus maximus (later Saurophaganax ). A. amplexus

25112-747: The taxonomy of Allosaurus . These include Marsh's Creosaurus and Labrosaurus , as well as Cope's Epanterias . In their haste, Cope and Marsh did not always follow up on their discoveries (or, more commonly, those made by their subordinates). For example, after the discovery by Benjamin Mudge of the type specimen of Allosaurus in Colorado, Marsh elected to concentrate work in Wyoming . When work resumed at Garden Park in 1883 , M. P. Felch found an almost complete Allosaurus and several partial skeletons. In addition, one of Cope's collectors, H. F. Hubbell, found

25284-402: The third finger has four. The legs were not as long or suited for speed as those of tyrannosaurids , and the claws of the toes were less developed and more hoof -like than those of earlier theropods. Each foot had three weight-bearing toes and an inner dewclaw , which Madsen suggested could have been used for grasping in juveniles. There was also what is interpreted as the splint-like remnant of

25456-418: The time of its discovery. The species epithet fragilis is Latin for "fragile", referring to lightening features in the vertebrae. The bones were collected from the Morrison Formation of Garden Park , north of Cañon City . O. C. Marsh and Edward Drinker Cope , who were in scientific competition with each other, went on to coin several other genera based on similarly sparse material that would later figure in

25628-412: The tiniest microorganism to God, is linked in a continuous chain. The extinction of a species was impossible under this model, as it would create gaps or missing links in the chain and destroy the natural order. Thomas Jefferson was a firm supporter of the great chain of being and an opponent of extinction, famously denying the extinction of the woolly mammoth on the grounds that nature never allows

25800-525: The tooth nondiagnostic but transferred it to Dryptosaurus , as D. medius . The referral was not accepted in the most recent review of basal tetanurans, and Allosaurus medius was simply listed as a dubious species of theropod. It may be closely related to Acrocanthosaurus . Allosaurus valens is a new combination for Antrodemus valens used by Friedrich von Huene in 1932; Antrodemus valens itself may also pertain to Allosaurus fragilis , as Gilmore suggested in 1920. A. lucaris , another Marsh name,

25972-567: The total extinction of the dodo and the extirpation of indigenous horses to the British Isles. He similarly argued against mass extinctions , believing that any extinction must be a gradual process. Lyell also showed that Cuvier's original interpretation of the Parisian strata was incorrect. Instead of the catastrophic floods inferred by Cuvier, Lyell demonstrated that patterns of saltwater and freshwater deposits , like those seen in

26144-491: The two had a contentious relationship. Othniel much preferred excursions in the woods to his chores. Among his childhood influences was Ezekiel Jewett, a former military officer and amateur scientist who influenced Othniel's interest in the sciences. Jewett had been drawn to the area by the fossils unearthed by the enlargement of the Erie Canal , and the two would hunt and prospect for specimens together. By 1847, Othniel

26316-458: The type species and was named by Marsh in 1877. It is known from the remains of at least 60 individuals, all found in the Kimmeridgian – Tithonian Upper Jurassic -age Morrison Formation of the United States, spread across Colorado , Montana , New Mexico , Oklahoma , South Dakota , Utah, and Wyoming. Details of the humerus (upper arm) of A. fragilis have been used as diagnostic among Morrison theropods, but A. jimmadseni indicates that this

26488-581: The wider scientific community of his theory. Cuvier was a well-regarded geologist, lauded for his ability to reconstruct the anatomy of an unknown species from a few fragments of bone. His primary evidence for extinction came from mammoth skulls found in the Paris basin . Cuvier recognized them as distinct from any known living species of elephant, and argued that it was highly unlikely such an enormous animal would go undiscovered. In 1812, Cuvier, along with Alexandre Brongniart and Geoffroy Saint-Hilaire , mapped

26660-519: Was a good student, but not a thrifty one; Aunt Judith, who was in charge of monitoring Marsh while Peabody was in Europe, regularly upbraided her nephew for his lax accounting habits and large expenses. Marsh graduated eighth in his class, using a scholarship he won for the best examination in Greek to finance a masters degree from Yale's Sheffield Scientific School , as he developed an interest in becoming

26832-595: Was a new combination by George Olshevsky for Megalosaurus meriani Greppin, 1870, based on a tooth from the Late Jurassic of Switzerland. However, a recent overview of Ceratosaurus included it in Ceratosaurus sp. Apatodon mirus , based on a scrap of vertebra Marsh first thought to be a mammalian jaw, has been listed as a synonym of Allosaurus fragilis . However, it was considered indeterminate beyond Dinosauria by Chure, and Mickey Mortimer believes that

27004-413: Was a subadult estimated at only 87% grown. The specimen was described by Breithaupt in 1996. Nineteen of its bones were broken or showed signs of serious infection, which may have contributed to "Big Al's" death. Pathologic bones included five ribs, five vertebrae, and four bones of the feet. Several of its damaged bones showed signs of osteomyelitis , a severe bone infection. A particular problem for

27176-500: Was a typical large theropod , having a massive skull on a short neck, a long, slightly sloping tail, and reduced forelimbs. Allosaurus fragilis , the best-known species, had an average length of 8.5 m (28 ft) and mass of 1.7 t (1.9 short tons), with the largest definitive Allosaurus specimen ( AMNH 680) estimated at 9.7 m (32 ft) long, with an estimated weight of 2.3–2.7 t (2.5–3.0 short tons). In his 1976 monograph on Allosaurus , James H. Madsen mentioned

27348-496: Was able to keep discovery teams in the field almost continuously from 1870 until his death. The material recovered in his 30 years of collection was simply astonishing to the scientific community. At the Peabody Museum, Marsh was the first to create skeletal displays of dinosaurs, which are now common in countless museums of natural history. Marsh biographer Mark J. McCarren summed it up this way, Marsh's "contributions to

27520-415: Was also present, but has only been recognized since 1996; in some cases furculae were confused with gastralia. The ilium , the main hip bone, was massive, and the pubic bone had a prominent foot that may have been used for both muscle attachment and as a prop for resting the body on the ground. Madsen noted that in about half of the individuals from the Cleveland-Lloyd Dinosaur Quarry , independent of size,

27692-660: Was attending school at the Wilson Collegiate Institute , and later attended the Lockport Union School. Othniel was undecided as to what he would do for a living, but the course of his future was dramatically changed due to the intervention of his uncle George Peabody , who was a successful banker. With Peabody's financial assistance (spurred by Marsh's aunt, Judith), Marsh enrolled in Phillips Academy in 1851. Older than most of

27864-576: Was coined by David Lambert in 1990 , being based on remains from Dinosaur National Monument assigned to Allosaurus or Creosaurus (a synonym of Allosaurus ), and was to be described by paleontologist Robert Bakker as "Madsenius trux". However, "Madsenius" is now seen as yet another synonym of Allosaurus because Bakker's action was predicated upon the false assumption of USNM 4734 being distinct from long-snouted Allosaurus due to errors in Gilmore's 1920 reconstruction of USNM 4734. "Wyomingraptor"

28036-473: Was created for this genus in 1878 by Othniel Charles Marsh , but the term was largely unused until the 1970s in favor of Megalosauridae , another family of large theropods that eventually became a wastebasket taxon . This, along with the use of Antrodemus for Allosaurus during the same period, is a point that needs to be remembered when searching for information on Allosaurus in publications that predate James Madsen's 1976 monograph. Major publications using

28208-491: Was difficult to disprove. When parts of the world had not been thoroughly examined and charted, scientists could not rule out that animals found only in the fossil record were not simply "hiding" in unexplored regions of the Earth. Georges Cuvier is credited with establishing the modern conception of extinction in a 1796 lecture to the French Institute , though he would spend most of his career trying to convince

28380-498: Was first reported in 1999 on the basis of MHNUL /AND.001, a partial skeleton including a quadrate , vertebrae, ribs, gastralia, chevrons , part of the hips, and legs. This specimen was assigned to A. fragilis , but the subsequent discovery of a partial skull and neck ( ML 415) near Lourinhã , in the Kimmeridgian-age Porto Novo Member of the Lourinhã Formation , spurred the naming of the new species as A. europaeus by Octávio Mateus and colleagues. The species appeared earlier in

28552-434: Was given to a partial skeleton in 1878. He later decided it warranted its own genus, Labrosaurus , but this has not been accepted, and A. lucaris is also regarded as another specimen of A. fragilis . Allosaurus lucaris , is known mostly from vertebrae, sharing characters with Allosaurus . Paul and Carpenter stated that the type specimen of this species, YPM 1931, was from a younger age than Allosaurus , and might represent

28724-673: Was informally coined by Bakker for allosaurid remains from the Morrison Formation of the Late Jurassic . The remains unearthed are labeled as Allosaurus and are housed in the Tate Geological Museum. However, there has been no official description of the remains and "Wyomingraptor" has been dismissed as a nomen nudum , with the remains referable to Allosaurus . Several species initially classified within or referred to Allosaurus do not belong within

28896-523: Was most common and was gradational, suggesting individual variation was responsible. Further work on size-related variation again found no consistent differences, although the Dry Mesa material tended to clump together on the basis of the astragalus , an ankle bone. Kenneth Carpenter , using skull elements from the Cleveland-Lloyd site, found wide variation between individuals, calling into question previous species-level distinctions based on such features as

29068-403: Was not different enough from Allosaurus to be a separate genus, but did warrant its own species, A. maximus . This reassignment was rejected in a review of basal tetanurans. There are also several species left over from the synonymizations of Creosaurus and Labrosaurus with Allosaurus . Creosaurus potens was named by Lull in 1911 for a vertebra from the Early Cretaceous of Maryland. It

29240-430: Was not until 1982, when David Raup and Jack Sepkoski published their seminal paper on mass extinctions, that Cuvier was vindicated and catastrophic extinction was accepted as an important mechanism . The current understanding of extinction is a synthesis of the cataclysmic extinction events proposed by Cuvier, and the background extinction events proposed by Lyell and Darwin. Extinction is an important research topic in

29412-419: Was originally coined by Cope in 1878 as the type species of his new genus Epanterias , and is based on what is now AMNH 5767, parts of three vertebrae, a coracoid , and a metatarsal. Following Paul's work, this species has been accepted as a synonym of A. fragilis . A 2010 study by Paul and Kenneth Carpenter, however, indicates that Epanterias is temporally younger than the A. fragilis type specimen, so it

29584-571: Was skeptical that catastrophic events of a scale large enough to cause total extinction were possible. In his geological history of the earth titled Hydrogeologie, Lamarck instead argued that the surface of the earth was shaped by gradual erosion and deposition by water, and that species changed over time in response to the changing environment. Charles Lyell , a noted geologist and founder of uniformitarianism , believed that past processes should be understood using present day processes. Like Lamarck, Lyell acknowledged that extinction could occur, noting

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