157-558: Kronosaurus ( / ˌ k r ɒ n oʊ ˈ s ɔːr ə s / KRON -oh- SOR -əs ) is an extinct genus of large short-necked pliosaur that lived during the Aptian to Albian stages of the Early Cretaceous in what is now Australia . The first known specimen was received in 1899 and consists of a partially preserved mandibular symphysis , which was first thought to come from an ichthyosaur according to Charles De Vis . However, it
314-557: A Cretoxyrhina -like shark . In 1899, a partial fossil of a marine reptile was sent on behalf of a certain Andrew Crombie to the Queensland Museum of Brisbane , Australia , and was received by the zoologist Charles De Vis , who was then the director of the museum during that time. No information regarding the origin locality of the fossil is known, but it seems that it was probably discovered near of Hughenden, Queensland ,
471-522: A derived pliosaurid, Hilary F. Ketchum still classifying it as a sister taxon of Brachauchenius in this family. Adam S. Smith and Gareth J. Dyke reclassify both genera within the Brachaucheniidae, but the family is seen as the sister taxon of the Pliosauridae. McHenry suggests that if Ketchum's proposal is proved as valid, then it would be preferable to relegate Brachaucheniidae as a subfamily of
628-438: 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
785-657: 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
942-563: A scientific article published in 1924 by the journal of the Queensland Museum. Longman deduces that the fossil comes from a large pliosaur , to which he gives the genus and species name Kronosaurus queenslandicus . The generic name comes from Kronos , a Titan from the Greek mythology , and from ancient Ancient Greek σαῦρος ( saûros , "lizard"), to literally give "lizard of Kronos". Longman would have created this generic name in reference to
1099-415: 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
1256-436: 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
1413-474: 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
1570-495: 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
1727-429: 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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#17328759904371884-399: 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
2041-708: 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
2198-405: 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
2355-592: 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
2512-538: A length of 8.9 meters (29 ft) with a body mass of 6.7 t (6.6 long tons; 7.4 short tons). The most complete known attributed specimen, QM F10113, would have reached slightly smaller measurements, namely 8.6 meters (28 ft) long with a body mass of 5.7 t (5.6 long tons; 6.3 short tons). The largest specimens of Kronosaurus having been discovered in the Toolebuc Formation, QM F2446 and QM F2454, would have reached measurements almost identical to that of
2669-459: A locality known as Army Downs. The latter had been aware for many years of the presence of "something strange coming out of the ground" in a small horse enclosure. These "strange things" were actually a row of vertebrae contained in nodules . Noticing his discovery, Thomas therefore informed the members of the Harvard expedition, and notably Schevill. The latter then contacts a British migrant trained in
2826-587: 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
2983-434: A message via telegraph informing journalists that it would be regrettable if such an important announcement made no mention of Longman and the interpretation of the initially fragmentary fossil material. At the age of 93, Thomas, the original discoverer of the specimen, was able to see the mounted skeleton of what he considered "his dinosaur", as well as meet again the leader of the museum's former expedition, each believing that
3140-589: A morphology typical of the pliosaurids of the thalassophonean group, which has a large elongated skull connected to a short neck , unlike many other plesiosaurs , which have a long neck and a small head. Like all other plesiosaurs, Kronosaurus has a short tail , a massive trunk and two pairs of large flippers . Kronosaurus is one of the largest pliosaurs identified to date, but several estimates as to its exact size have been proposed during research. As early as 1930, Longman, in his description of propodiums, considered that Kronosaurus would have exceeded in size
3297-456: 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
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#17328759904373454-441: 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,
3611-506: A new taxon that the two authors name Eiectus longmani , in homage to Longman, the paleontologist who named the original genus. The Harvard skeleton (MCZ 1285) is also designated a holotype of this same genus. In 2023, Valentin Fischer and colleagues criticized the reassignments even under these circumstances, predicting that they stand contrary to ICZN Articles 75.5 and 75.6 and that the aforementioned multiple-species possibility cannot justify
3768-458: A now obsolete taxon which included plesiosaurs and ichthyosaurs . De Vis initially thought the specimen came from an ichthyosaur, specifically Ichthyosaurus australis , which today seems to be placed in the genus Platypterygius . However, the particular dentition of this specimen quickly makes it change its mind about whether it belongs to this specific genus. The fossil was officially described by De Vis's successor, Albert Heber Longman , in
3925-610: 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
4082-407: 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
4239-502: 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
4396-486: 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
4553-563: A smaller size of this specimen between 9 and 10.5 meters (30 and 34 ft) long for a weight of 11 t (11 long tons; 12 short tons). These same measurements are seen as the maximum possible estimates of the genus as a whole. Even before McHenry's thesis was published, paleontologist Benjamin P. Kear and marine biologist Richard Ellis proposed comparable estimates in their respective works both published in 2003, ranging from 9 meters (30 ft) according to Kear at 10.6 meters (35 ft) according to Ellis. In 2024, Ruizhe Jackevan Zhao revises
4710-479: 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
4867-439: 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
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5024-404: 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
5181-518: 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
5338-469: A tentative reassignment of all specimens to Eiectus . The authors instead opted to refer to all relevant fossils as Kronosaurus-Eiectus . The same year, Stephen F. Poropat and colleagues maintained K. queenslandicus as a nominally valid taxon that includes all fossils from the Toolebuc and Allaru Formation pending an official ICZN petition, recommending specimen QM F18827 as neotype. The authors also criticize
5495-462: A town from which Crombie comes. Queensland Museum records show that De Vis even sent a letter to Crombie informing him that he had been made aware of the receipt of the material. The fossil in question, cataloged as QM F1609, consists of a partial mandibular symphysis bearing six conical teeth . Based on his observations, De Vis considers the fossil to come from a representative of the Enaliosauria ,
5652-626: A wingspan exceeding 5 m (16 ft). De Vis initially suggested that the Kronosaurus holotype specimen belonged to an ichthyosaur. However, when Longman described the taxon in 1924, he assigned it to the family Pliosauridae based on multiple anatomical features, an affiliation which will be mainly recognized throughout the 20th century as well as in the 21st century by the scientific community . However, some alternative classifications have been proposed throughout research. For example, in 1962, Welles suggested that Kronosaurus possibly belonged to
5809-550: Is a cladogram showing the phylogenetic relationships of living and extinct sea turtles in the Chelonioidea based on Evers et al. (2019): † Toxochelys † Protostegidae [REDACTED] † Corsochelys Dermochelyidae [REDACTED] † Nichollsemys † Allopleuron Cheloniidae [REDACTED] † Argillochelys † Procolpochelys † Eochelone † Puppigerus † Ctenochelys † Peritresius † Cabindachelys An alternate phylogeny
5966-517: 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
6123-444: 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
6280-585: 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
6437-417: 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
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6594-453: Is estimated to be 2.85 metres (9.4 ft) long. The cranial measurements of the last three specimens previously cited surpass in size the skull of any known theropod dinosaurs . The snout and the mandibular rostrum are long and narrow in shape. The rostrum in general appears to be arched in shape and is relatively elongated, possessing a distinct median and dorsal crest. The eye sockets face posteriorly, where they are located laterally on
6751-834: Is modified from Madzia et al. (2018): Peloneustes philarchus 'Pliosaurus' andrewsi Simolestes vorax Liopleurodon ferox Pliosaurus patagonicus Pliosaurus almanzaensis 'Pliosaurus' irgisensis Pliosaurus rossicus Gallardosaurus iturraldei Pliosaurus brachyspondylus Pliosaurus macromerus Pliosaurus brachydeirus Pliosaurus westburyensis Pliosaurus kevani Pliosaurus cf. kevani Pliosaurus carpenteri Pliosaurus funkei Makhaira rossica Luskhan itilensis Stenorhynchosaurus munozi cf. Kronosaurus queenslandicus (QM F51291) Kronosaurus queenslandicus Megacephalosaurus eulerti ' Polyptychodon interruptus ' (DORK/G/1-2) cf. Brachauchenius lucasi (MNA V9433) Extinct Extinction
6908-625: Is possible to tell male turtles from female turtles by their long tails with a cloacal opening near the tip. Adult female sea turtles have shorter tails, with a cloacal opening near the base. Hatchling and sub-adult turtles do not exhibit sexual dimorphism ; it is not possible to determine their sex by looking at them. In general, sea turtles have a more fusiform body plan than their terrestrial or freshwater counterparts. This tapering at both ends reduces volume and means that sea turtles cannot retract their head and limbs into their shells for protection, unlike many other turtles and tortoises. However,
7065-402: Is temporarily referred to Eiectus , and that it is only a matter of time before CT scans can reveal whether or not the specimen belongs to Kronosaurus . Many Kronosaurus specimens preserve postcranial material. The most complete specimen known, cataloged as QM F10113, preserves an important part of the postcranial anatomy which would reveal important information for a more in-depth diagnosis of
7222-592: 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
7379-525: 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
7536-466: Is the smallest sea turtle species, to 120 cm (3.9 ft) long in the case of the green turtle, the second largest. The skulls of sea turtles have cheek regions that are enclosed in bone. Although this condition appears to resemble that found in the earliest known fossil reptiles (anapsids), it is possible it is a more recently evolved trait in sea turtles, placing them outside the anapsids. Sea turtles, along with other turtles and tortoises, are part of
7693-457: 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
7850-468: The SS Canadian Constructor around 1 December 1932. Once arrived at Harvard, the fossils, which represent approximately 60% of the skeleton, took several years to extract from the limestone . The lack of money, manpower and space within the museum is the cause of the long delays, and it will take until 1939 only for the skull to be mounted and exhibited. However, a first scientific description of
8007-518: The Australian state of its discovery. In the early 1930s, the Harvard Museum of Comparative Zoology sent an organized expedition to Australia that recovered two specimens historically attributed to the taxon , including a well known skeleton that is now massively restored in plaster . Several attributed fossils were subsequently discovered, including two large, more or less partials skeletons. As
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#17328759904378164-512: The Bulldog Shale . In his 2009 thesis, McHenry describes in detail many fossils attributed to Kronosaurus , including most of the new specimens that he judges to possibly belong to this genus. Of the numerous fossil specimens that he analyzed, McHenry proposed that two partial skeletons, cataloged as QM F10113 and QM F18827, which both come from the Toolebuc Formation, could be candidate neotypes , because they present features that seem to fit with
8321-521: The Cabot Corporation . Cabot's family had a history of sighting large sea snakes in the coastal waters around the town he is from. When questioning the museum's director, Alfred Sherwood Romer , about the existence and reports of sea serpents, it occurred to Romer to tell Cabot about the skeleton kept in the museum's basement. So Cabot asks about the cost of a restoration and Romer says "about $ 10,000". Romer may not have been serious, but Cabot clearly
8478-461: The IUCN Red List of Threatened Species. The flatback turtle is found only in the waters of Australia, Papua New Guinea, and Indonesia. Sea turtles can be categorized as hard-shelled ( cheloniid ) or leathery-shelled ( dermochelyid ). The only dermochelyid species of sea turtle is the leatherback. For each of the seven species of sea turtles, females and males are the same size. As adults, it
8635-474: 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
8792-576: The Late Cretaceous aquatic squamate Mosasaurus hoffmannii would reach around 18 meters (59 ft) long, the latter having a reduced size to around 11 meters (36 ft) according to more recent estimates. Currently, the largest marine reptile identified to date is the Late Triassic ichthyosaur Ichthyotitan , which is thought to have reached around 25 meters (82 ft) in length. The Harvard skeleton restoration being erroneous, McHenry gives
8949-477: 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
9106-579: The Rolling Downs geological group , north of the town of Richmond, where he collected two large pliosaur specimens. These same specimens are collected from the Doncaster Member of the Wallumbilla Formation , dating back approximately 112 million years. The first specimen he exhumed, cataloged as MCZ 1284 and discovered on a property called Grampian Valley, consisted of a well-preserved piece of
9263-550: The Toolebuc Formation , dating from the Albian stage of the Early Cretaceous , the holotype having very probably also been discovered in this same locality. The majority of the material recovered is then very incomplete, the only two that can be concretely described being proximal parts of propodials (upper limb bones), which are analyzed in more detail the following year, and those again by Longman. In 1932, in an effort to make
9420-619: 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 , such as 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
9577-587: The sister group to the Chelonoidea, or an unrelated turtle lineage that convergently evolved similar adaptations. The earliest "true" sea turtle that is known from fossils is Nichollsemys from the Early Cretaceous ( Albian ) of Canada . In 2022, the giant fossil species Leviathanochelys was described from Spain . This species inhabited the oceans covering Europe in the Late Cretaceous and rivaled
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#17328759904379734-410: 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
9891-484: 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,
10048-441: The tail of Kronosaurus is unknown, the end of the caudal vertebrae would have supported a small caudal fin like in other plesiosaurs. The coracoid and pubis are both elongated from front to back. The hind limbs of Kronosaurus are longer than its forelimbs, with the femur being longer and robust than the humerus . This suggests that the largest representatives of Kronosaurus would have rear flippers which would have formed
10205-619: 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
10362-451: 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,
10519-605: 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
10676-402: The Harvard skeleton "a rather disappointing restoration of what must have been an excellent fossil specimen". For this reason, many researchers express their desire to analyze real fossils using CT scans . Given that the holotype specimen of K. queenslandicus (QM F1609) is fragmentary and does not present any unique characteristics that would qualify the genus as distinct from other pliosaurs,
10833-508: The Harvard skeleton. However, the latter having been reconstructed with an exaggerated number of vertebrae , estimates published from the early 2000s reduce the size of the animal from 9 m (30 ft) to more than 10 m (33 ft) long. Like all plesiosaurs, Kronosaurus has four paddle-like limbs, a short tail and, like most pliosaurids, a long head and a short neck. The largest identified skulls of Kronosaurus dwarf those of largest known theropod dinosaurs in size. The front of
10990-418: The Harvard skeleton. Respectively, these two specimens would have reached 10.2 to 10.5 meters (33 to 34 ft) in length with body masses estimated at 9.9 to 15.5 t (9.7 to 15.3 long tons; 10.9 to 17.1 short tons). Since the holotype of K. queenslandicus (QM F1609) consists of only a partial mandibular symphysis, very little can be said about it. However, more complete fossil skulls that are assigned to
11147-453: The Harvard specimen (MCZ 1285). Longman, in his letters to Schevill, suggests that he would have enjoyed seeing the specimen during its preparation in the late 1930s, but it never left Australian territory. The rest of the skeleton was kept in the basement of the museum for more than fifteen years. This interim period ended when the fossils attracted the attention of Godfrey Lowell Cabot , a Boston industrialist, philanthropist and founder of
11304-570: 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
11461-518: 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
11618-453: The Pliosauridae, therefore being renamed Brachaucheninae. McHenry nevertheless maintains the name Brachaucheniidae in his thesis detailing in more detail Kronosaurus pending further phylogenetic results. In 2013, Roger B. S. Benson and Druckenmiller named a new clade within Pliosauridae, Thalassophonea . This clade included the "classic", short-necked pliosaurids while excluding the earlier, long-necked, more gracile forms. The authors thus move
11775-551: The Toolebuc Formation, more precisely from the Telemon station, about 30 km west of Hughenden. Among all the fossils Young was involved in exhuming are additional remains attributed to Kronosaurus , including the first somewhat more complete cranial parts identified within the genus. In his article published in October 1935, Longman, due to the high number of fossils, suggested that they came from at least two or three individuals. Noting that
11932-534: The Toolebuc Formation, the formation from which the first fossils attributed to the genus were discovered. In other formations, only one additional attributed specimen was discovered in the Doncaster Member of the Wallumbilla Formation, while three specimens, including one attributed to the type species , were discovered in the Allaru Formation . Two specimen with no specific affiliation were identified in
12089-529: The Toolebuc Formation. To determine whether this statement is true, only a CT scan could reveal the presence of the true notable differences within this reconstructed plaster specimen. In 1977, an almost complete skeleton of a large pliosaur was discovered by local residents of the town of Villa de Leyva , Colombia. The specimen, nicknamed " El Fósil " and dating from the Upper Aptian of the Paja Formation ,
12246-486: The United States government, to force the removal of Native Americans , many of whom relied on the bison for food. Sea turtle Chelonii - Oppel, 1811 Chlonopteria - Rafinesque, 1814 Cheloniae - Schmid, 1819 Edigitata - Haworth, 1825 Oiacopodae - Wagler, 1828 Pterodactyli - Mayer, 1849 Sea turtles (superfamily Chelonioidea ), sometimes called marine turtles , are reptiles of
12403-429: 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
12560-423: The administrative division where the specimen was discovered. Due to the fact that the holotype specimen of Kronosaurus is non-diagnostic, the majority of anatomical descriptions are based on observations made from more complete fossils later assigned to the genus. The majority of descriptions come from McHenry's thesis published in 2009, although some specimens have been described in other works. Kronosaurus has
12717-558: The animal would have reached between 15,000 to 27,000 newtons (3,370 to 6,070 lbf), surpassing the placoderm Dunkleosteus and rivaling Tyrannosaurus , but being largely outnumbered by the megalodon . The skull of a juvenile specimen shows that it would have been attacked by an adult , indicating intraspecific aggression or even potential evidence of cannibalism within the genus. Kronosaurus would have faced interspecific competition with other large predators within this sea, with one specimen attributed showing bite marks from
12874-464: The animal's fossils "attractive", Longman published one of the oldest known reconstructions of Kronosaurus . The illustration was drawn in 1931 by a certain Wilfrid Morden, who was inspired in particular by the anatomical features of Peloneustes to fill in the still unknown parts of the animal. In May and April 1935, a certain J. Edgar Young for the Queensland Museum, collected several fossils from
13031-482: The anterior rostrum closely connected to the entire mandibular symphysis, in addition to several other fragmentary pieces. The story regarding the discovery, exhumation and exhibition of the second specimen, cataloged as MCZ 1285, is much more detailed in many historical sources. This specimen was discovered long before the Harvard Expedition was even launched, by a rancher named Ralph William Haslam Thomas, in
13188-408: The anterior half of the skull. The temporal fossae (openings in the back of the cranium) are very large, but does not have an anterior interpterygoid vacuity. One of the many traits identified as unique in Kronosaurus is that the premaxilla (front upper tooth-bearing bones) has 4 caniniform teeth. The frontal bones (bones bordering the eye sockets) do not come into contact with the margin of
13345-463: The back pair larger than the front. The flippers would have given a wingspan of more than 5 m (16 ft) for the largest representatives. Phylogenetic classifications published since 2013 recover Kronosaurus within the subfamily Brachaucheninae , a lineage which includes numerous pliosaurids that lived during different stages of the Cretaceous. Based on its stratigraphic distribution in
13502-427: The cervical centra (vertebral bodies) are wider than the dorsals . The anterior dorsal vertebrae are nevertheless higher than wide. The zygapophyses would have been visibly absent from the anterior dorsal vertebrae and in the caudal vertebrae . In the thoracic region, the ribs would have been robust, as suggested by the transverse processes which are equally robust. The ribs would also been single-headead. Although
13659-566: The concurrent giant protostegids such as Archelon and Protostega as one of the largest turtles to ever exist. Unlike the protostegids, which have an uncertain relationship to modern sea turtles, Leviathanochelys is thought to be a true sea turtle of the superfamily Chelonioidea. Sea turtles' limbs and brains have evolved to adapt to their diets. Their limbs originally evolved for locomotion, but more recently evolved to aid them in feeding. They use their limbs to hold, swipe, and forage their food. This helps them eat more efficiently. Below
13816-600: 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
13973-418: 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
14130-471: 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
14287-403: 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
14444-575: 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
14601-443: 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
14758-475: 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
14915-442: The eye sockets due to their connections between the postfrontal and prefrontal bones . The frontal bones also do not come into contact with the middle part of the skull roof due to their connections between the parietal bones and facial processes of the premaxillae. The prefrontals are large and contact the anteromedial part of the eye sockets as well as the posterior border of the nostrils . The lacrimal bones (bones bordering
15072-573: The fact that the museum had relatively few Australian animals and therefore wanted to collect more. It was then that the Harvard Australian Expedition began, and was undertaken by a team of six men. The team consisted of coleopterologist P. Jackson Darlington Jr. , zoologist Glover Morrill Allen and his student Ralph Nicholson Ellis, chief physician Ira M. Dixon, paleontologist William E. Schevill , and their leader, entomologist William Morton Wheeler . The following year, in 1932, it
15229-431: The family Brachaucheniidae as a subfamily, renaming it Brachaucheninae, and classify many Cretaceous pliosaurids there, including Kronosaurus . Within this subfamily, Kronosaurus appears to be one of the most derived representatives, being generally placed in a clade including Brachauchenius and more recently Megacephalosaurus . Subsequent studies have uncovered a similar position for Kronosaurus . The cladogram below
15386-474: The family Dolichorhynchopidae. However, this family is today recognized as polyphyletic (unnatural grouping) and is seen as invalid. The exact phylogenetic positioning of Kronosaurus within the Pliosauridae has also been debated. In 1992, Hampe proposed to classify Kronosaurus with its close relative Brachauchenius in the proposed family Brachaucheniidae. Kenneth Carpenter agreed with Hampe in 1996, although noting some notable cranial differences between
15543-533: 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
15700-525: The first marine turtle is Angolachelys , from the Turonian of Angola. A lineage of unrelated marine testudines, the pleurodire (side-necked) bothremydids , also survived well into the Cenozoic. Other pleurodires are also thought to have lived at sea, such as Araripemys and extinct pelomedusids . Modern sea turtles are not descended from more than one of the groups of sea-going turtles that have existed in
15857-435: 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
16014-466: The fossil record, Kronosaurus inhabited the Eromanga Sea , an ancient inland sea that covered a large part of Australia during the Early Cretaceous. This inner sea reached cold temperatures close to freezing . Kronosaurus would likely have been an apex predator in this sea, with fossil evidence showing that it preyed on sea turtles and other plesiosaurs. Estimates of its bite force suggest that
16171-582: The fossils were not fully prepared at the time of his description, he describes them preliminary. The most notable specimen, cataloged as QM F2446, consists of a partial middle of the skull which preserves an occipital condyle , the back of the neurocranium , the external nostrils as well as the orbits . In 1931, the Museum of Comparative Zoology sent an expedition to Australia with the dual aim of obtaining specimens of both living and extinct animals, and in particular marsupial mammals . This decision came from
16328-403: The front of the jaws, while the smaller teeth are more sharply recurved, stouter, and located further back. The Harvard skeleton historically attributed to Kronosaurus received a study detailing its postcranial anatomy by Romer and Lewis in 1959. However, as the latter was massively restored in plaster, it is currently difficult to discern it with real fossil material. Additionally, the specimen
16485-580: 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
16642-660: 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
16799-447: 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
16956-439: The holotype is so massively restored with plaster that all features apparent diagnostics are probably unreliable without comprehensive CT scans. Although the only currently recognized species of Kronosaurus is K. queenslandicus , several authors have suggested the existence of additional species within the genus. In 1982 and again in 1991, Ralph Molnar expressed doubts as to whether the Harvard skeleton (MCZ 1285) belonged to
17113-467: The holotype specimen does not present diagnostics to concretely distinguish Kronosaurus from other pliosaurids, these same two skeletons are proposed as potential neotypes for future redescriptions. Two additional species were proposed, but these are now seen as unlikely or belonging to another genus. Kronosaurus is one of the largest known pliosaurs identified to date. Initial estimates set its maximum size at around 13 m (43 ft) long based on
17270-454: The holotype. However, no formal ICZN petition to designate a neotype was submitted. In 2022, Leslie Francis Noè and Marcela Gómez-Pérez published a study that revised most of the specimens historically attributed to Kronosaurus . Both authors limit Kronosaurus only to the holotype and consider it a nomen dubium . The holotype specimen does not possess any features allowing a diagnostic, the other attributed fossils are provisionally moved to
17427-475: 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
17584-476: The imposing Megalneusaurus , a North American pliosaurid dating from the Late Jurassic . After the collection of fossils assigned to the genus by the Harvard Expedition, the maximum size of Kronosaurus was generally set at 12.8 meters (42 ft) long,based on specimen MCZ 1285. Kronosaurus was then considered as being the largest known marine reptile until 1995, when Theagarten Lingham-Soliar suggested that
17741-614: The imposing size and possible ferocity of the animal, which could recall the story of Kronos, who is known in Greek mythology for having devoured his own children, notably Zeus . The specific epithet queenslandicus is named after the Queensland , the Australian state where the holotype specimen was most likely discovered. In August 1929, fifteen more or less partial fossils are discovered nearly 3.2 km south of Hughenden. These same fossils, all catalogued as QM F2137, are identified as coming from
17898-431: 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,
18055-502: The lineage ( Panchelonioidea ) leading to modern sea turtles was possibly Desmatochelys padillai from the Early Cretaceous. Desmatochelys was a protostegid , a lineage that would later give rise to some very large species but went extinct at the end of the Cretaceous. Presently thought to be outside the crown group that contains modern sea turtles (Chelonioidea), the exact relationships of protostegids to modern sea turtles are still debated due to their primitive morphology; they may be
18212-538: The lower front edges of the eye sockets) are present in small specimens, but tend to be fused in adults. The dorsal surface of the median dorsal crest is formed by the premaxillae and nasal bones (bones bordering the external nares), of which in adults are fused. The hyoid bones are robust. The mandibular symphysis of Kronosaurus is elongated and spatulate (spoon-shaped), and like its close relatives Brachauchenius and Megacephalosaurus , it contains up to 6 pairs of teeth. Each dentary (the tooth-bearing bone in
18369-485: 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
18526-400: The mandible) have up to 26 teeth. The mandibular glenoid (socket of the jaw joint ) is kidney-shaped and angled upwards and inwards. The main autapomorphy of Kronosaurus teeth is that they are conical in shape, roughly ridged, and lacking distinct carinae. The dentition of Kronosaurus is heterodont , that is, it has teeth of different shapes. The larger teeth are caniniform and located at
18683-410: The measurements of MCZ 1285 at 10.3 meters (34 ft). Other specimens have been given body estimates although some of these are only known from more limited fossil remains. QM F1609, the holotype specimen, although very fragmentary, would have measured 5.9 meters (19 ft) long with a body mass of 1.9 t (1.9 long tons; 2.1 short tons). The proposed neotype specimen QM F18827 would have reached
18840-421: 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
18997-490: 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
19154-469: 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
19311-410: 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
19468-524: The order Testudines and of the suborder Cryptodira . The seven existing species of sea turtles are the flatback , green , hawksbill , leatherback , loggerhead , Kemp's ridley , and olive ridley . Six of the seven sea turtle species, all but the flatback, are present in U.S. waters, and are listed as endangered and/or threatened under the Endangered Species Act . All but the flatback turtle are listed as threatened with extinction globally on
19625-540: The order Testudines . All species except the leatherback sea turtle are in the family Cheloniidae . The superfamily name Chelonioidea and family name Cheloniidae are based on the Ancient Greek word for tortoise: χελώνη ( khelōnē ). The leatherback sea turtle is the only extant member of the family Dermochelyidae . Fossil evidence of marine turtles goes back to the Late Jurassic (150 million years ago) with genera such as Plesiochelys , from Europe. In Africa,
19782-399: 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
19939-400: The other had been dead for a long time. The arrival of new knowledge in the field of paleontology subsequently calls into question the restoration of the skeleton as proposed by Romer. Indeed, because of many incomplete bones, the latter ordered Lewis and Jensen to add plaster where he deemed it necessary. This latest decision has made it difficult for paleontologists to access real fossils, to
20096-457: The past; they instead constitute a single radiation that became distinct from all other turtles at least 110 million years ago. Their closest extant relatives are in fact the snapping turtles (Chelydridae), musk turtles (Kinosternidae), and hickatee ( Dermatemyidae ) of the Americas, which alongside the sea turtles constitute the clade Americhelydia . The oldest possible representative of
20253-495: The point where some of them use the nickname " Plasterosaurus " to refer to the specimen. In addition, it seems that the skeleton was reconstructed with the wrong proportions. According to Australian paleontologist Colin McHenry, the specimen has 8 extra vertebrae added to the spine and the skull is not supposed to have a bulbous shaped sagittal crest on top. In his thesis revising the genus Kronosaurus published in 2009, McHenry called
20410-702: 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
20567-410: 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
20724-497: The repurposing of Toolebuc specimens, on the grounds that Noè and Gómez-Pérez presumably ignored the conclusion of McHenry's 2009 thesis that only one species of large pliosaur exists in the formation and that, therefore, all of its specimens can be reliably considered conspecific to the holotype. As for Eiectus , Poropat and colleagues limit it only to MCZ 1285 and the referred specimen MCZ 1284, but their assignment without formal redescription also remains subject to debate, given that
20881-426: The skull is elongated into a rostrum (snout). The mandibular symphysis, where the front ends of each side of the mandible (lower jaw) fuse, is elongated in Kronosaurus , and contains up to six pairs of teeth. The large cone-shaped teeth of Kronosaurus would have been used for a diet consisting of large prey. The front teeth are larger than the back teeth. The limbs of Kronosaurus were modified into flippers, with
21038-459: The skull was made by Theodore E. White in 1935. One year earlier, in 1934, Schevill asked Longman to send a cast of the holotype mandibular symphysis for comparison with the new specimen. It was then Longman's assistant, a certain Tom Marshall, who took it upon himself to make Schevill's request. The researchers then realized that the characters of the holotype (QM F1609) were identical to those of
21195-402: The species K. queenslandicus , given that it was discovered in a locality distinct from that of the first known specimens, namely in the older Wallumbilla Formation. The author therefore suggests that this specimen would belong to another species of Kronosaurus characterized by a deeper and more robust skull than those coming from the Toolebuc Formation. A study published in 1993 also attributes
21352-460: 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
21509-508: The specimen under the name Kronosaurus sp., the authors following the same opinion as Molnar. However, as White indicates in his description of the specimen in 1935, much of the skull roof is not preserved and is mostly restored in plaster, the real proportions being therefore uncertain. In his 2009 thesis, McHenry nevertheless continues to refer the specimen to K. queenslandicus because of its taphonomic distribution and certain traits which may be consistent with other specimens discovered in
21666-454: The specimen was prohibited by the local community. In addition, the state of preservation of the specimen and anatomical characteristics different from those of K. queenslandicus also suggested doubts about the affiliation of this species to Kronosaurus . It was therefore in 2022 that Noè and Gómez-Pérez re-described this specimen and discovered that it belonged to a distinct genus, which they named Monquirasaurus , in reference to Monquirá ,
21823-464: The streamlined body plan reduces friction and drag in the water and allows sea turtles to swim more easily and swiftly. The leatherback sea turtle is the largest sea turtle, reaching 1.4 to more than 1.8 m (4.6 to 5.9 ft) in length and weighing between 300 and 640 kg (661 to 1,411 lbs). Other sea turtle species are smaller, ranging from as little as 60 cm (2 ft) long in the case of the Kemp's ridley, which
21980-430: 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
22137-408: The taxon show unique traits . The skulls of various known specimens of Kronosaurus vary in size. The holotype, which although partial and fragmentary, comes from a skull which would have measured a total of 1.31 metres (4.3 ft) long. Candidate neotype specimens QM F10113 and QM F18827 have cranial lengths reaching 1.87–1.98 metres (6.1–6.5 ft), respectively. The skull of the Harvard skeleton
22294-427: The taxon. This same specimen should also be described in more detail in a future study. Some features concerning the postcranial anatomy of the genus have however been noted, both in McHenry's thesis and in other articles. Based on the different specimens analyzed, McHenry estimates that Kronosaurus would have had at least 35 presacral vertebrae , including 13 cervical and 5 pectoral vertebra. Unlike Pliosaurus ,
22451-412: 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
22608-555: 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
22765-469: The two genera. The family Brachaucheniidae was originally erected in 1925 by Samuel Wendell Williston to include only Brachauchenius . In 2001, F. Robin O'Keefe revised the classification of Pliosauridae and classified Kronosaurus as a basal representative distantly related to Brachauchenius . In 2008, two studies and a thesis proposed alternative classifications for Kronosaurus . Patrick S. Druckenmiller and Anthony P. Russell classified Kronosaurus as
22922-399: The use of explosives, nicknamed "The Maniac" by local residents, in order to extract the specimen of 4.5 metric tons (5.0 short tons) of rock which constitutes its geological matrix . When the specimen was unearthed, its fossils were then sent to the United States in 86 crates weighing a total of 6 metric tons (6.6 short tons). According to the export permit, the specimen was transported aboard
23079-461: The validity of this taxon has therefore been questioned. As early as 1962, Samuel Paul Welles considered Kronosaurus as a nomen vanum and recommended the designation of a neotype specimen from Harvard University which would preserve the genus validity. From 1979, a good number of fossils from large pliosaurs were discovered in various localities in Australia, mainly in the geological strata of
23236-577: 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
23393-478: Was 1924 that Albert Heber Longman formally described this specimen as the holotype of an imposing pliosaurid , to which he gave the scientific name K. queenslandicus , which is still the only recognized species nowadays. The genus name , meaning "lizard of Kronos ", refers to its large size and possible ferocity reminiscent of the Titan of the Greek mythology , while the species name alludes to Queensland ,
23550-544: Was Schevill who acquired the title of expedition leader, making long journeys and recruiting local help when he could. The Queensland Museum was also invited to participate in this expedition, but this was never approved due to lack of funds and/or interest from the state government. However, Longman, who described the first known fossils of Kronosaurus , nevertheless assisted the expedition, storing specimens as they were sent to him, securing collecting permits, and maintaining correspondence with Schevill. Schevill then ventured into
23707-453: Was because the check for said sum came shortly after. Given that Romer's primary interest was the study of non-mammalian synapsids , it is possible that he had little regard for the skeleton as a subject of scientific study. After two years of careful preparations with chisel and acid by Arnold Lewis and James A. Jensen under Romer's direction, their work ultimately cost slightly more than promised by Cabot's base check. The Harvard skeleton
23864-483: 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
24021-455: Was exhibited for the first time on 10 June 1958, and is followed by a detailed scientific description carried out by Romer and Lewis, which was published the following year by the museum journal. When the finalization of the specimen was announced in the Australian press, Longman, who is the descriptor of the taxon, was not mentioned. In response, professor and geologist Walter Heywood Bryan sent
24178-479: Was first provisionally referred to the genus Kronosaurus two years later, in 1979. It was in 1992 that the German paleontologist Olivier Hampe established a second species of the genus under the name of K. boyacensis , the specific name referring to Boyacá , the department surrounding the discovery site. However, these descriptions were made from photographs and remote imaging techniques, in particular because access to
24335-430: 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
24492-508: Was proposed by Castillo-Visa et al. (2022): † Toxochelyidae † Protostegidae † Corsochelys † Eosphargis Dermochelys † Nichollsemys † Leviathanochelys † Allopleuron † Procolpochelys † Argillochelys † Eochelone † Puppigerus † Cabindachelys † Ctenochelys † Peritresius Natator Eretmochelys Chelonia Lepidochelys kempii Caretta Lepidochelys olivacea Sea turtles can be found in all oceans except for
24649-571: 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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