162-487: Aetosaurs ( / eɪ ˌ ɛ t oʊ ˈ s ɔːr / ) are heavily armored reptiles belonging to the extinct order Aetosauria ( / eɪ ˌ ɛ t oʊ ˈ s ɔːr i ə / ; from Greek , ἀετός (aetos, "eagle") and σαυρος ( sauros , "lizard")). They were medium- to large-sized omnivorous or herbivorous pseudosuchians , part of the branch of archosaurs more closely related to crocodilians than to birds and other dinosaurs . All known aetosaurs are restricted to
324-438: 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
486-657: 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
648-415: 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
810-436: 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
972-474: 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
1134-495: 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
1296-486: A close relative of aetosaurs originally misidentified as a juvenile desmatosuchine. The outer two rows of osteoderms, which lie beside the paramedians, are known as lateral osteoderms. They parallel the paramedians over nearly the entire backside, though the first two paramedians behind the head (known as nuchal osteoderms) are solitary. Lateral plates generally are separated into two surfaces, or flanges, flexed between their dorsal eminence. The upper, or dorsal flange lies in
1458-429: 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
1620-606: A distinct species by others. Pigs were domesticated in the Neolithic , both in East Asia and in the Near East. When domesticated pigs arrived in Europe, they extensively interbred with wild boar but retained their domesticated features. Pigs are farmed primarily for meat, called pork . The animal's skin or hide is used for leather . China is the world's largest pork producer, followed by
1782-404: A distinct group, Aetosauria was named in 1889 by English naturalist Richard Lydekker and zoologist Henry Alleyne Nicholson . They considered Aetosauria to be one of three suborders of the order Crocodilia, the other two being Parasuchia (a group including phytosaurs and other Triassic forms) and Eusuchia (a group including all post-Triassic crocodylomorphs). Nicholson and Lydekker placed
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#17329267690141944-399: 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
2106-424: A group called Suchia , which included many Triassic crurotarsans as well as later crurotarsans, including crocodilians. Originally, all aetosaurs were considered members of the family Stagonolepididae. Early phylogenetic analyses split aetosaurs into two subfamilies, Aetosaurinae and Desmatosuchinae. Aetosaurines are characterized by projections called eminences on the dorsal paramedian osteoderms that are close to
2268-488: A healthy, full-grown adult. Vietnamese Pot-bellied pigs, a miniature breed of pig , have been kept as pets in the United States, beginning in the latter half of the 20th century. Pigs are intelligent, social creatures. They are considered hypoallergenic and are known to do quite well with people who have the usual animal allergies. Since these animals are known to have a life expectancy of 15 to 20 years, they require
2430-708: 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
2592-419: A keratinous (horn) covering, like modern crocodilian scutes , which are another example of pseudosuchian osteoderms. Osteoderms are useful in diagnosing aetosaur taxa, and aetosaur species can often be identified from individual scutes based on their shape, structure, or ornamentation pattern. Aetosaurs have four rows of osteoderms running along their dorsal (back) side, forming a continuous plate often called
2754-405: 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
2916-592: 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
3078-453: A litter of piglets, once per year. By the nineteenth century, European piglets routinely double-farrowed, or bore two litters of piglets per year. It is unclear when this shift occurred. Pigs have a maximum life span of about 27 years. A characteristic of pigs which they share with carnivores is nest-building . Sows root in the ground to create depressions the size of their body, and then build nest mounds, using twigs and leaves, softer in
3240-466: A long snout strengthened by a special prenasal bone and a disk of cartilage at the tip. The snout is used to dig into the soil to find food and is an acute sense organ. The dental formula of adult pigs is 3.1.4.3 3.1.4.3 , giving a total of 44 teeth . The rear teeth are adapted for crushing. In males, the canine teeth can form tusks , which grow continuously and are sharpened by grinding against each other. There are four hoofed toes on each foot;
3402-534: A long-term commitment. Given pigs are bred primarily as livestock and have not been bred as companion animals for very long, selective breeding for a placid or biddable temperament is not well established. Pigs have radically different psychology and behaviours compared to dogs, and exhibit fight-or-flight instincts, an independent nature, and natural assertiveness . Male and female swine that have not been de-sexed may express unwanted aggressive behavior, and are prone to developing serious health issues. As rooting
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#17329267690143564-587: 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
3726-926: A more modern view of aetosaurian anatomy and ecology. Aetosaur fossils have been found on all continents except Australia and Antarctica , giving them a nearly worldwide distribution during the Late Triassic. Aetosaur remains are most abundant in northern ( Laurasian ) continents, and fossils are particularly common in the Chinle Formation and Dockum Group of the southwestern United States . Most fossils have been found in Arizona , New Mexico , and Texas . Some remains have also been found in Wyoming , Colorado , and Utah , particularly in Canyonlands National Park and Zion National Park . Aetosaurs are also known from
3888-456: 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
4050-649: A new aetosaur was named from the Lower Dharmaram Formation of India as Venkatasuchus armatus , a typothoracine aetosaur. Reports of aetosaurs from Madagascar are based on probable crocodylomorph scutes. Supposed aetosaurian footprints and skeletal material from South Africa are also unsubstantiated. Footprints belonging to the ichnogenus Brachychirotherium are often associated with aetosaurs. Brachychirotherium are known from Rio Grande do Sul in Paleorrota, Brazil as well as Italy , Germany ,
4212-441: 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,
4374-455: A now extinct ghost population of wild pigs during the Pleistocene . The genomes of domestic pigs show strong selection for genes affecting behavior and morphology. Human selection for domestic traits likely counteracted the homogenizing effect of gene flow from wild boars and created domestication islands in the genome. Pigs arrived in Europe from the Near East at least 8,500 years ago. Over
4536-610: 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
4698-407: 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
4860-502: 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
5022-400: A related grade of carnivorous Triassic pseudosuchians ancestral to crocodylomorphs. A pillar-erect limb posture is one where the femur articulates vertically with the acetabulum of the hip, which is angled downward, so that the leg is positioned beneath the body and acts as a weight-bearing pillar. Nevertheless, there was likely significant variation in the hip structure of aetosaurs, and
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5184-486: 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
5346-666: A separate species. Archaeological evidence shows that pigs were domesticated from wild boar in the Near East in or around the Tigris Basin, being managed in a semi-wild state much as they are managed by some modern New Guineans. There were pigs in Cyprus more than 11,400 years ago, introduced from the mainland, implying domestication in the adjacent mainland by then. Pigs were separately domesticated in China, starting some 8,000 years ago. In
5508-468: A short time and then sleep for a short time. Pigs are omnivorous and versatile in their feeding behaviour. They primarily eat leaves, stems, roots, fruits, and flowers. Rooting is an instinctual comforting behaviour in pigs characterized by nudging the snout into something. It first happens when piglets are born to obtain their mother's milk, and can become a habitual, obsessive behaviour, most prominent in animals weaned too early. Pigs root and dig into
5670-403: A shoulder height of 1.5 m (4 ft 11 in). Pigs possess both apocrine and eccrine sweat glands , although the latter are limited to the snout. Pigs, like other "hairless" mammals such as elephants, do not use thermal sweat glands in cooling. Pigs are less able than many other mammals to dissipate heat from wet mucous membranes in the mouth by panting. Their thermoneutral zone
5832-456: A simplified, crowded, or uncomfortable environment may resort to tail-biting ; farmers sometimes dock the tails of pigs to prevent the problem, or may enrich the environment with toys or other objects to reduce the risk. Because of their relative lack of sweat glands, pigs often control their body temperature using behavioural thermoregulation. Wallowing , coating the body with mud, is a common behaviour. They do not submerge completely under
5994-860: A single family within the suborder, Aëtosauridæ. They considered aetosaurs to be similar to living crocodilians despite their longer metatarsals. Aetosaur material continued to be described into the early 20th century, with notable paleontologists such as Barnum Brown and Charles Camp collecting specimens. Better remains of American aetosaurs helped to establish anatomical info for some common species, such as Desmatosuchus spurensis (described in detail by E.C. Case in 1922) and "Typothorax" meadei (now Longosuchus , described by H.J. Sawin in 1947). However, aetosaur remains were still being confused with those of phytosaurs, and they were still considered to be predominantly carnivorous and semiaquatic "parasuchians" . A.D. Walker 's 1961 redescription of Stagonolepis robertsoni helped to divert these notions and established
6156-479: 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
6318-439: 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
6480-404: 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
6642-518: 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
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6804-488: A target on screen. Pigs have panoramic vision of approximately 310° and binocular vision of 35° to 50°. It is thought they have no eye accommodation . Other animals that have no accommodation, e.g. sheep, lift their heads to see distant objects. The extent to which pigs have colour vision is still a source of some debate; however, the presence of cone cells in the retina with two distinct wavelength sensitivities (blue and green) suggests that at least some colour vision
6966-414: A teat, the more milk that teat later releases. In pigs, dominance hierarchies are formed at an early age. Piglets are precocious, and attempt to suckle soon after being born. The piglets are born with sharp teeth and fight for the anterior teats, as these produce more milk. Once established, this teat order remains stable; each piglet tends to feed on a particular teat or group of teats. Stimulation of
7128-1436: A third group, Typothoracinae, which like Desmatosuchinae has long spikes, but differs in having more sharply angled joints between osteoderms. Moreover, the genus Aetosauroides is now often classified outside Stagonolepididae as a non-stagonolepidid aetosaur, making the names Aetosauria and Stagonolepididae no longer synonymous. Acaenasuchus [REDACTED] USA (Arizona) Chinle Formation ( Blue Mesa Member , Sonsela Member ) Acompsosaurus [REDACTED] USA (New Mexico) Chinle Group ( Bluewater Creek Formation ) Adamanasuchus [REDACTED] USA (Arizona) Chinle Formation ( Blue Mesa Member ) Aetobarbakinoides [REDACTED] Brazil Santa Maria Formation An aetosaur with aetosaurine-like osteoderms and desmatosuchine-like vertebrae. Aetosauroides [REDACTED] Argentina , [REDACTED] Brazil Ischigualasto Formation , Santa Maria Formation Aetosaurus middle Norian - early Rhaetian ? (Revueltian) [REDACTED] Germany , [REDACTED] Italy , [REDACTED] Greenland Lower Stubensandtein , Calcare di Zorzino Formation , Fleming Fjord Formation Apachesuchus [REDACTED] USA Redonda Formation Argentinosuchus [REDACTED] Argentina Ischigualasto Formation Extinct Extinction
7290-481: A year, usually in spring or early summer, to prepare for the warmer months ahead. Where pigs are allowed to roam freely, they walk roughly 4 km daily, scavenging within a home range of around a hectare. Farmers in Africa often choose such a low-input, free-range production system. If conditions permit, pigs feed continuously for many hours and then sleep for many hours, in contrast to ruminants , which tend to feed for
7452-458: A ziphodont shape, meaning that the teeth are recurved, serrated, and flattened from the side. This shape, which is predominant in Aetosauroides and a small specimen tentatively referred to Coahomasuchus , is typical of carnivorous archosaurs. In some aetosaurs (particular members of the group Desmatosuchia), the tip of the snout is expanded sideways into a flattened 'shovel' shape, akin to
7614-499: Is 16–22 °C (61–72 °F). At higher temperatures, pigs lose heat by wallowing in mud or water via evaporative cooling, although it has been suggested that wallowing may serve other functions, such as protection from sunburn, ecto-parasite control, and scent-marking. Pigs are among four mammalian species with mutations in the nicotinic acetylcholine receptor that protect against snake venom . Mongooses , honey badgers , hedgehogs , and pigs all have different modifications to
7776-517: 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
7938-444: 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
8100-625: Is considered ambiguous. The skull of aetosaurs is relatively small compared to the body, and is quite distinctive in shape. Teeth are absent from both the front of the premaxilla (the bone forming the tip of the snout) and the front of the dentary (the toothed bone of the lower jaw). The teeth which are present are usually small and bulbous, ranging from basic conical forms to leaf-like shapes with large serrations. These are probably indicative of an omnivorous or herbivorous diet, and similar adaptations are seen in other archosaurs with less reliance on meat in their diet. A few aetosaurs have teeth with
8262-585: 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
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#17329267690148424-475: Is especially an issue in southeastern South America. Female pigs reach sexual maturity at 3–12 months of age and come into estrus every 18–24 days if they are not successfully bred. The variation in ovulation rate can be attributed to intrinsic factors such as age and genotype, as well as extrinsic factors like nutrition, environment, and the supplementation of exogenous hormones. The gestation period averages 112–120 days. Estrus lasts two to three days, and
8586-417: 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
8748-420: Is found to be comforting, pigs kept in the house may root household objects, furniture or surfaces. Pet pigs should be let outside to allow them to fulfill their natural desire of rooting around. Approximately 1.5 billion pigs are slaughtered each year for meat. The pork belly futures contract became an icon of commodities trading . It appears in depictions of the arena in popular entertainment, such as
8910-861: Is generally one of the most useful traits for inferring aetosaur relations more precisely. Among other archosaurs, aetosaurs are most closely related to Revueltosaurus , a small reptile originally known from teeth mistakenly referred to herbivorous dinosaurs. Aetosaur remains were first discovered in the early 19th century, although the first remains that were described were mistaken for fish scales . Aetosaurs were later recognized as crocodile relatives, at which point they were interpreted as semiaquatic scavengers closely related to phytosaurs . Subsequent work has established that aetosaurs were entirely terrestrial animals, and were likely herbivorous to some extent. Some forms have characteristics that may have been adaptations to digging for food. Supposed nesting structures have also been referred to aetosaurs, but this connection
9072-450: Is most often considered to be a subspecies of the wild boar , which was given the name Sus scrofa by Carl Linnaeus in 1758; following from this, the formal name of the pig is Sus scrofa domesticus . However, in 1777, Johann Christian Polycarp Erxleben classified the pig as a separate species from the wild boar. He gave it the name Sus domesticus , still used by some taxonomists. The American Society of Mammalogists considers it
9234-400: Is present. Pigs have a well-developed sense of smell; this is exploited in Europe where trained pigs find underground truffles . Pigs have 1,113 genes for smell receptors, compared to 1,094 in dogs; this may indicate an acute sense of smell, but against this, insects have only around 50 to 100 such genes but make extensive use of olfaction. Olfactory rather than visual stimuli are used in
9396-405: Is set at a low position, and the articular (the bone of the lower jaw which connects to the cranium) often has a tall projection right behind the jaw joint. In most respects apart from their skull and armor, the skeletal anatomy of aetosaurs was fairly standard among other large Triassic pseudosuchians. The hindlimbs developed a "pillar-erect" limb posture similar to that seen in " rauisuchians ",
9558-571: Is some variation in the degree of this trend. The typothoracines , exemplified by Typothorax and Paratypothorax , had a very broad, disc-shaped carapace, edged by small spines or keels and transitioning to a narrow tail. The largest species of typothoracines may have been around 3 meters (9.8 feet) in length and 110 kg (243 lbs) in weight. The desmatosuchines ( Desmatosuchinae sensu stricto ), such as Desmatosuchus and Longosuchus , had moderately narrower bodies and no belly armor. However, they also acquired spinier back armor, especially in
9720-592: 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
9882-525: 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
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#173292676901410044-457: 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
10206-477: The Geological Society of London in 1858, and went into more detail in an 1875 paper in the society's quarterly journal. By this time, new material had been uncovered from Elgin that indicated that Stagonolepis was not a fish, but a reptile. However, Stagonolepis was still known primarily by scutes and imprints of scutes, many of which were not well preserved. More complete aetosaur remains were found from
10368-474: 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
10530-477: 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
10692-677: The Late Triassic , and in some strata from this time they are among the most abundant fossil vertebrates . They have small heads, upturned snouts, erect limbs, and a body ornamented with four rows of plate-like osteoderms (bony scutes ). Aetosaur fossil remains are known from Europe , North and South America , parts of Africa , and India . Since their armoured plates are often preserved and are abundant in certain localities, aetosaurs serve as important Late Triassic tetrapod index fossils . Many aetosaurs had wide geographic ranges, but their stratigraphic ranges were relatively short. Therefore,
10854-594: The Lower Stubensandtein of Germany in the 1870s. Among them were complete articulated skeletons of 22 aetosaurs. These specimens were found in a large sandstone outcrop near Stuttgart and were preserved together in an area less than 2 square metres in size. The animals were probably buried under lake sediment soon after they died, with the flow of water repositioning their bodies on the lake bed and putting them in close proximity to one another. In 1877, German paleontologist Oscar Fraas assigned these specimens to
11016-611: The Midwest , where many state agencies have programs to remove them. Feral pigs in New Zealand and northern Queensland have caused substantial environmental damage. Feral hybrids of the European wild boar with the domestic pig are disruptive to both environment and agriculture, as they destroy crops, spread animal diseases including Foot-and-mouth disease , and consume wildlife such as juvenile seabirds and young tortoises . Feral pig damage
11178-740: The Newark Supergroup along the East Coast of the United States, in states such as Connecticut and North Carolina . Aetosaurus and Paratypothorax have been recovered from the Fleming Fjord Formation of Jameson Land , on the east coast of Greenland . These two genera were originally named from the Lower Stubensandstein of Germany. Scotland , Poland , and Italy have also produced aetosaur fossils. A few aetosaurs are known from northern Africa, with scutes having been found from
11340-492: The carapace . The inner two rows, which flank the midline of the spinal column, are known as paramedian osteoderms. These tend to be wider than long and strongly ornamented with radiating pits or grooves. Nearly all aetosaurs possess a small boss or raised surface, known as a dorsal eminence, on the upper surface of each plate. The dorsal eminence is often set posteriorly (backwards) or medially (inwards) on their respective paramedian osteoderm, though there are many exceptions within
11502-619: 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
11664-410: 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
11826-484: 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,
11988-455: The tick -borne African Swine Fever , bacterial infections such as Clostridium , arthritis caused by Mycoplasma , and stillbirths caused by Parvovirus . Some parasites of pigs are a public health risk as they can be transmitted to humans in undercooked pork. These are the pork tapeworm Taenia solium ; a protozoan, Toxoplasma gondii ; and a nematode, Trichinella spiralis . Transmission can be prevented by thorough sanitation on
12150-619: 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
12312-451: 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,
12474-711: The Carnian Ischigualasto Formation and Norian Los Colorados Formation , respectively. In Brazil, fossils have been found in the Santa Maria and Caturrita Formations in Rio Grande do Sul (Paleorrota). Chilean aetosaurs are represented by one fragmentary genus, Chilenosuchus , from the Antofagasta Region . Aetosaurs have also been found in India , which, along with South America, was part of Gondwana during
12636-605: 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
12798-462: The European Union and then the United States. Around 1.5 billion pigs are raised each year, producing some 120 million tonnes of meat, often cured as bacon . Some are kept as pets . Pigs have featured in human culture since Neolithic times, appearing in art and literature for children and adults, and celebrated in cities such as Bologna for their meat products. The pig has a large head, with
12960-539: The Late Triassic. Early accounts of Indian aetosaurs were based on material from the Maleri Formation in south-central India, although most of these remains were too inadequate to assign specimens to any particular genus. Based on published descriptions, the Indian aetosaur fossils most closely resemble Longosuchus and Paratypothorax, which are considerably more specialized than most described Gondwanan aetosaurs. In 2023
13122-500: The Late Triassic. While new material referable to Typothorax has been found in recent years throughout the American southwest, Episcoposaurus is no longer considered valid. Cope, along with later paleontologists such as Friedrich von Huene , recognized that remains of the type species E. horridus actually belonged to Typothorax . At the time, Cope considered Aetosauria to belong to Rhynchocephalia , an order of reptiles that includes
13284-478: The Near East, pig husbandry spread for the next few millennia. It reduced gradually during the Bronze Age , as rural populations instead focused on commodity-producing livestock, but it was sustained in cities. Domestication did not involve reproductive isolation with population bottlenecks. Western Asian pigs were introduced into Europe, where they crossed with wild boar. There appears to have been interbreeding with
13446-604: The Near Eastern genes dying out in European pig stock. More recently there have been complex exchanges, with European domesticated lines being exported, in turn, to the ancient Near East. Historical records indicate that Asian pigs were again introduced into Europe during the 18th and early 19th centuries. Among the animals that the Spanish introduced to the Chiloé Archipelago in the 16th century Columbian Exchange , pigs were
13608-570: 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
13770-518: 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
13932-484: The United States government, to force the removal of Native Americans , many of whom relied on the bison for food. Pig The pig ( Sus domesticus ), also called swine ( pl. : swine) or hog , is an omnivorous , domesticated , even-toed, hoofed mammal . It is named the domestic pig when distinguishing it from other members of the genus Sus . It is considered a subspecies of Sus scrofa (the wild boar or Eurasian boar) by some authorities, but as
14094-429: 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
14256-553: The anterior teats appears to be important in causing milk letdown, so it might be advantageous to the entire litter to have these teats occupied by healthy piglets. Piglets locate teats by sight and then by olfaction. Pig behaviour is intermediate between that of other artiodactyls and of carnivores . Pigs seek out the company of other pigs and often huddle to maintain physical contact, but they do not naturally form large herds. They live in groups of about 8–10 adult sows, some young individuals, and some single males. Pigs confined in
14418-498: The back, sides, belly, and tail. These osteoderms generally have a quadrangular (four-sided) shape, and were most certainly used as a defense against predators. Most osteoderms are heavily pitted on their upper surfaces and smooth on their undersides. They have a heterogenous internal structure: the inner portion of each osteoderm is made of cancellous or spongy bone (also called diploë ) and their outer portions are made up of compact bone. In life, these plates were probably covered in
14580-414: The boar's corkscrew-shaped penis during copulation. Females have bicornuate uteruses and two conceptuses must be present in both uterine horns to enable pregnancy to proceed. The mother's body recognises that it is pregnant on days 11 to 12 of pregnancy, and is marked by the corpus luteum 's producing the sex hormone progesterone . To sustain the pregnancy, the embryo signals to the corpus luteum with
14742-419: The body in response to their heavy armor: the iliofibularis muscle attached to a lower position on the fibula , the fourth trochanter of the femur was enlarged, the transverse processes (rib attachments) developed into long massive pedestals, and the largest species even acquired hyposphene-hypantrum reinforcements between their vertebrae. Although aetosaurs were generally wide-bodied reptiles, there
14904-415: The cervical (neck) region. Desmatosuchus was likely one of the largest known aetosaurs, at 4–6 m (13–20 ft) in length and 280 kg (620 lb) in weight. Aetosaurs which do not fit into these two categories, such as Stagonolepis and Neoaetosauroides , generally had narrow forms, slender limbs, and a restriction in the carapace above the hip. This body type is plesiomorphic (ancestral) to
15066-600: 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
15228-418: 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
15390-471: 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
15552-470: The domesticated pig is one of the most numerous large mammals on the planet. Like all animals, pigs are susceptible to adverse impacts from climate change , such as heat stress from increased annual temperatures and more intense heatwaves . Heat stress has increased rapidly between 1981 and 2017 on pig farms in Europe. Installing a ground-coupled heat exchanger is an effective intervention. Around 600 breeds of pig have been created by farmers around
15714-503: The eastern United States, and many other aetosaur-bearing locales. They are also common in the southwestern United States, having been found in Canyonlands National Park and Dinosaur National Monument . Many of these tracks have a narrow gauge (meaning the left and right prints are placed closely together) and nearly overstep each other. A 2011 functional analysis of the skeleton of Typothorax coccinarum indicated that it had
15876-403: 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
16038-575: 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
16200-443: 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
16362-475: 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
16524-457: The farm; by meat inspection and careful commercial processing; and by thorough cooking, or alternatively by sufficient freezing and curing. Pigs have been raised outdoors, and sometimes allowed to forage in woods or pastures. In industrialized nations, pig production has largely switched to large-scale intensive pig farming . This has lowered production costs but has caused concern about possible cruelty . As consumers have become concerned with
16686-417: The female's displayed receptiveness to mate is known as standing heat. Standing heat is a reflexive response that is stimulated when the female is in contact with the saliva of a sexually mature boar. Androstenol is one of the pheromones produced in the submaxillary salivary glands of boars that trigger the female's response. The female cervix contains a series of five interdigitating pads, or folds, that hold
16848-533: 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
17010-416: The flow stops and so does the grunting of the sow. The piglets may dart from teat to teat and recommence suckling with slow movements, or nosing the udder. Piglets massage and suckle the sow's teats after milk flow ceases as a way of letting the sow know their nutritional status. This helps her to regulate the amount of milk released from that teat in future sucklings. The more intense the post-feed massaging of
17172-498: The forelimbs may have had a semi-sprawling 'hybrid' stance. While the hindlimb posture is similar to rauisuchians, other traits are more plesiomorphic (typical to ancestral pseudosuchians), such as the stout pelvis and broad, five-toed feet. The forelimbs were smaller than the hind limbs, and the radius in particular was much shorter than the humerus . Nevertheless, their low and heavy body shape requires that all aetosaurs were quadrupeds . They had multiple adaptations to strengthen
17334-435: 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
17496-588: The front and hindlimbs. Aetosaur material was first described by Swiss paleontologist Louis Agassiz in 1844. He named the genus Stagonolepis from the Lossiemouth Sandstone in Elgin , Scotland , but considered the fossil to be a Devonian fish rather than a Triassic reptile. This may be because he considered the strata to be part of the Old Red Sandstone , and thus Paleozoic in age. Agassiz mistook
17658-464: The ground to forage for food. Rooting is also a means of communication. Pigs are relatively intelligent animals, roughly on par with dogs . They distinguish each other as individuals, spend time in play, and form structured communities. They have good long-term memory and they experience emotions, changing their behaviour in response to the emotional states of other pigs. In terms of experimental tasks, pigs can perform tasks that require them to identify
17820-697: The group. The paramedian osteoderms almost always have raised or depressed anterior edges, where the plates are overlapped by the ones in front of them. If the anterior edge is raised, the area is called an anterior bar, while if it is depressed, the area is called an anterior lamina. Although two paramedian osteoderm rows are common in early archosauriforms, few reptiles approach aetosaurs in the complexity of their osteoderms. The osteoderms of doswelliids , erpetosuchids , and certain crocodylomorphs are occasionally confused or compared with those of aetosaurs. Both an anterior bar and dorsal eminence occur in Acaenasuchus ,
17982-580: 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
18144-660: 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
18306-446: The herd. This ensures they do not get trampled on, and prevents other piglets from stealing milk from the sow. The onset of nest-building is triggered by a rise in prolactin level, caused by a decrease in progesterone and an increase in prostaglandin; the gathering of nest material seems to be regulated more by external stimuli such as temperature. Pigs have complex nursing and suckling behaviour. Nursing occurs every 50–60 minutes, and
18468-454: The hip, leaving a wide gap for the cloacal opening. Large, hooked spines occur around this opening in Typothorax , one of the few exceptions to a general rule of smooth ventral osteoderms. Ventral rows break up into a shagreen of small plates on the neck, and a small number of wide rows under the tail. A dense assortment of small, non-overlapping plates, known as appendicular osteoderms, covered
18630-447: 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
18792-480: The hormones estradiol and prostaglandin E2 . This signaling acts on both the endometrium and luteal tissue to prevent the regression of the corpus luteum by activation of genes that are responsible for corpus luteum maintenance. During mid to late pregnancy, the corpus luteum relies primarily on luteinizing hormone for maintenance until birth. Archeological evidence indicates that medieval European pigs farrowed, or bore
18954-475: 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
19116-458: The humane treatment of livestock, demand for pasture-raised pork in these nations has increased. Most pigs in the US receive ractopamine , a beta-agonist drug , which promotes muscle instead of fat and quicker weight gain, requiring less feed to reach finishing weight, and producing less manure . China has requested that pork exports be ractopamine-free. With a population of around 1 billion individuals,
19278-568: The identification of other pigs. Hearing is well developed; sounds are localised by moving the head. Pigs use auditory stimuli extensively for communication in all social activities. Alarm or aversive stimuli are transmitted to other pigs not only by auditory cues but also by pheromones . Similarly, recognition between the sow and her piglets is by olfactory and vocal cues. Pigs are subject to many pests and diseases which can seriously affect productivity and cause death. These include parasites such as Ascaris roundworms, virus diseases such as
19440-431: 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,
19602-933: The late Carnian Timesgadiouine Formation in Morocco. During the Late Triassic, Morocco would have been in close proximity with the Newark Supergroup of North America in the supercontinent of Pangaea . It is also possible that Desmatosuchus was present in Africa, as fossils from the Zarzaitine Series in Algeria have been referred to the genus. Aetosaurs are also found in areas corresponding to Gondwana (southern Pangaea), though they are considerably less common or diverse than in Northern continents. South American aetosaurs are known from Argentina , Brazil , and Chile . In Argentina, Aetosauroides and Neoaetosauroides hail from
19764-419: The living tuatara . He also thought that the tightly fitting osteoderms, which were thought to be fused to the ribs, indicated that aetosaurs were transitional between rhynchocephalians and turtles . Another species, E. haplocerus , was reassigned to Desmatosuchus in 1953. A third North American genus called Stegomus was named by Othniel Charles Marsh in 1896. Marsh had a long-time rivalry with Cope that
19926-432: The locations of objects; they can solve mazes; and they can work with a simple language of symbols. They display self-recognition in a mirror . Pigs have been trained to associate different sorts of music (Bach and a military march) with food and social isolation respectively, and could communicate the resulting positive or negative emotion to untrained pigs. Pigs can be trained to use a joystick with their snout to select
20088-485: 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
20250-399: The middle, in which to give birth. When the mound reaches the desired height, she places large branches, up to 2 metres in length, on the surface. She enters the mound and roots around to create a depression within the gathered material. She then gives birth in a lying position, unlike other artiodactyls which usually stand while birthing. Nest-building occurs during the last 24 hours before
20412-606: The midline of the back. Desmatosuchines have a few more distinguishing characteristics, including grooves on the dorsal paramedians that help them lock to the lateral plates in a tight articulation. Many desmatosuchines have long spikes projecting from the lateral plates. These spikes are especially prominent in Desmatosuchus . Aetosaurines, on the other hand, tend to have less spikes. Many aetosaurines, such as Aetosaurus and Neoaetosauroides , have smooth carapaces and lack spikes altogether. More recent studies (see below ) have favored
20574-421: 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
20736-443: The most successful in adapting to local conditions. The pigs benefited from abundant shellfish and algae exposed by the large tides of the archipelago. Pigs were brought to southeastern North America from Europe by de Soto and other early Spanish explorers . Escaped pigs became feral . Pigs have escaped from farms and gone feral in many parts of the world. Feral pigs in the southeastern United States have migrated north to
20898-405: The mud, but vary the depth and duration of wallowing depending on environmental conditions. Adult pigs start wallowing once the ambient temperature is around 17–21 °C (63–70 °F). They cover themselves in mud from head to tail. They may use mud as a sunscreen, or to keep parasites away. Most bristled pigs "blow their coat", meaning that they shed most of the longer, coarser stiff hair once
21060-490: 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
21222-469: 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
21384-410: 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
21546-508: The newly erected genus Aetosaurus . Fraas named the genus after the skull's resemblance to the head of an eagle, with a narrow, elongate skull and a pointed snout. The first aetosaurs from North America were also being described in the 1870s. American paleontologist Edward Drinker Cope named Typothorax in 1875 and Episcoposaurus in 1877, both of which were from New Mexico . However, Cope considered these genera to be phytosaurs , crocodile-like aquatic archosaurs that were also common in
21708-431: The next 3,000 years they interbred with European wild boar until their genome showed less than 5% Near Eastern ancestry, yet retained their domesticated features. DNA evidence from subfossil remains of teeth and jawbones of Neolithic pigs shows that the first domestic pigs in Europe were brought from the Near East. This stimulated the domestication of local European wild boar, resulting in a third domestication event with
21870-402: The onset of farrowing, and becomes most intense 12 to 6 hours before farrowing. The sow separates from the group and seeks a suitable nest site with well-drained soil and shelter from rain and wind. This provides the offspring with shelter, comfort, and thermoregulation. The nest provides protection against weather and predators, while keeping the piglets close to the sow and away from the rest of
22032-399: 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
22194-421: The osteoderms for large rhomboidal scales, which he thought were arranged in a similar pattern to those of gars . He also thought that these supposed scales were very similar to those of the lobe-finned fish Megalichthys due to their large size. English biologist Thomas Henry Huxley reconsidered the fish scales described by Agassiz and considered them to belong to a crocodilian. He first proposed this to
22356-600: The other two shapes, with some narrow-bodied aetosaurs more closely related to typothoracines and others closer to desmatosuchines. Some plesiomorphic genera, like the widespread Norian genus Aetosaurus and the Carnian Coahomasuchus , tended to be small, about a metre (3.2 ft) in length. Others were larger, such as the basal -most aetosaur Aetosauroides and the early desmatosuchine Calyptosuchus . Aetosaurs were very heavily armored, with rows of large, interlocking bony plates, known as osteoderms , protecting
22518-517: The presence of particular aetosaurs can accurately date a site in which they are found. Nearly all aetosaurs (except for the genus Aetosauroides ) belong to the family Stagonolepididae . Over 20 genera of aetosaurs have been described, and recently there has been controversy regarding the description of some of these genera. Two distinct subdivisions of aetosaurs are currently recognized, Desmatosuchia and Aetosaurinae , based primarily on broad differences in skull morphology . Osteoderms structure
22680-702: 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
22842-508: The range of movement necessary to produce the tracks. Aetosaurs belong to Pseudosuchia , a clade of archosaurs that includes living crocodilians and is characterized by the distinctive structure of the ankle bones . Aetosaurs were traditionally referred to a (now obsolete) group called the thecodonts , which included all " primitive " crocodilian relatives that lived in the Triassic. With the rise of phylogenetics , aetosaurs were later placed in
23004-795: The receptor pocket which prevents α-neurotoxin from binding. Pigs have small lungs for their body size, and are thus more susceptible than other domesticated animals to fatal bronchitis and pneumonia . The genome of the pig has been sequenced; it contains about 22,342 protein -coding genes . Domestic pigs are related to other pig species as shown in the cladogram , based on phylogenetic analysis using mitochondrial DNA . Babirusa [REDACTED] Red river hog [REDACTED] Warthogs [REDACTED] Visayan warty pig [REDACTED] Philippine warty pig [REDACTED] Bornean bearded pig [REDACTED] Javan warty pig [REDACTED] [REDACTED] East Asian pigs [REDACTED] European pigs [REDACTED] The pig
23166-410: 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
23328-440: The same plane as the paramedian osteoderms. The lower/outer, or lateral flange wraps down onto the side of the body. The dorsal eminence between these flanges often has the form of a low blade, knob, or spike. In the cervical lateral osteoderms, which are positioned on the neck, the dorsal eminence tends to manifest as a prominent spike. This is taken to an extreme in desmatosuchines such as Longosuchus and Desmatosuchus , where
23490-416: The skull, a hole known as the supratemporal fenestra is positioned and exposed on the side, unlike most other archosaurs where it is mostly visible when viewing the skull from above. The braincase is fairly standard by pseudosuchian standards, though the opening for the abducens nerve passes through the parabasisphenoid bone (at the lower front part of the braincase), rather than the prootic bone (at
23652-414: The snout of a pig . The external nares (nostril holes) are elongated, much larger than the antorbital fenestrae (a hole on the side of the skull). Many aetosaurs have a small knob on the premaxilla which projects into the nares from below. In all aetosaurs except Aetosauroides , the rear edge of the naris receives a contribution from the concave front edge of the maxilla bone . At the rear upper part of
23814-469: The sow grunts at slow, regular intervals. Each series of grunts varies in frequency, tone and magnitude, indicating the stages of nursing to the piglets. The phase of competition for teats and of nosing the udder lasts for about a minute, ending when milk begins to flow. The piglets then hold the teats in their mouths and suck with slow mouth movements (one per second), and the rate of the sow's grunting increases for approximately 20 seconds. The grunt peak in
23976-406: The sow requires stimulation from piglets before milk let-down. Sensory inputs (vocalisation, odours from mammary and birth fluids, and hair patterns of the sow) are particularly important immediately post-birth to facilitate teat location by the piglets. Initially, the piglets compete for position at the udder; then the piglets massage around their respective teats with their snouts, during which time
24138-460: 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
24300-424: The spike is enlarged into a sharply curved horn. In most aetosaurs (a major exception being desmatosuchines ), the underside of the animal is also protected by osteoderms. These ventral (belly) osteoderms are generally smaller and flatter than the dorsal series, and are arranged into a larger number of rows (usually 5 - 14 rows), at least in the torso. Ventral osteoderms rows usually curve outwards and separate under
24462-430: 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
24624-452: The third phase of suckling does not coincide with milk ejection, but rather the release of oxytocin from the pituitary into the bloodstream. Phase four coincides with the period of main milk flow (10–20 seconds) when the piglets suddenly withdraw slightly from the udder and start sucking with rapid mouth movements of about three per second. The sow grunts rapidly, lower in tone and often in quick runs of three or four, during this phase. Finally,
24786-412: 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
24948-555: 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
25110-492: The two larger central toes bear most of the weight, while the outer two are also used in soft ground. Most pigs have rather sparsely bristled hair on their skin, though there are some woolly -coated breeds such as the Mangalitsa . Adult pigs generally weigh between 140 and 300 kg (310 and 660 lb), though some breeds can exceed this range. Exceptionally, a pig called Big Bill weighed 1,157 kg (2,551 lb) and had
25272-493: The upper front part). This trait is otherwise only seen in Revueltosaurus and crocodylomorphs among archosaurs. The mandible (lower jaw) is described as 'slipper'-shaped in many aetosaurs. This is due to a combination of features: the front of the dentary strongly tapers to a point, while the underside of the dentary sometimes flexes into a 'chin' (downwards projection) which may expose the splenial bone as well. The jaw joint
25434-577: 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
25596-628: The world, mainly in Europe and Asia, differing in coloration, shape, and size. According to The Livestock Conservancy , as of 2016, three breeds of pig are critically rare (having a global population of fewer than 2000). They are the Choctaw hog , the Mulefoot , and the Ossabaw Island hog . The smallest known pig breed in the world is the Göttingen minipig , typically weighing about 26 kilograms (57 lb) as
25758-483: 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
25920-701: Was made famous in the Bone Wars of the late 19th century, in which the two tried to out-compete one another in the field and in scientific literature. Unlike Cope's aetosaurs, Stegomus was found from the eastern United States in Connecticut . Marsh also recognized Stegomus as an aetosaur rather than a phytosaur in his initial description of the genus. Like Cope, many paleontologists tended to consider aetosaur scutes to belong to phytosaurs during this time period. Marsh considered aetosaurs to be closely related to dinosaurs based on their elongated metatarsals (foot bones). As
26082-430: 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
26244-571: 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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