111-492: Osteodontornis is an extinct seabird genus . It contains a single named species , Osteodontornis orri ( Orr's bony-toothed bird , in literal translation of its scientific name ), which was described quite exactly one century after the first species of the Pelagornithidae ( Pelagornis miocaenus ) was. O. orri was named after Santa Barbara Museum of Natural History paleontologist Phil C. Orr, for his recognition of
222-438: 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
333-657: 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
444-415: 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
555-436: 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
666-512: A working hypothesis until sufficient well-preserved material has been found to make an in-depth study. It is less clear what to make of the Southern Hemisphere pseudotooth birds fossils, none of which are complete enough for more than the most tentative identification. Many seabirds of our time, such as albatrosses and other Procellariiformes , show a phylogenetic division between Northern and Southern Hemisphere lineages, separated by
777-474: 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
888-495: 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
999-429: 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
1110-593: A distinct but closely related genus, and it must be remembered that at that their time the Isthmus of Panama had not been formed yet so that an affiliation with the Atlantic Pelagornis cannot be discounted. The former, specimen MBLUZ -P-5093 from Cueva del Zumbador in Falcón State , is a premaxilla tip of immense dimensions; its bearer might have exceeded a wingspan of 7 metres (23 ft) in life. Though some of
1221-399: 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
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#17330925317471332-708: 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
1443-405: 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
1554-592: 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
1665-587: 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
1776-490: A more narrowly grooved dorsal head, and a larger and less forward-pointing orbital process. The forward center of the ventral articulation ridge extends upwards and forward, and the pterygoid process is conspicuously expanded to the upper center in Osteodontornis . The socket for the quadratojugal has an intermediate position and the lateral ridge of the slender main shaft is straight and fairly thin. The quadrate of
1887-456: 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
1998-441: 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,
2109-610: 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
2220-407: 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
2331-502: 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
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#17330925317472442-486: 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
2553-479: 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
2664-439: 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
2775-404: 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
2886-518: 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
2997-461: A very reliable way to distinguish genera . In general lifestyle, it was probably most similar to the albatrosses , tropicbirds and frigatebirds of today, with long slender wings adapted for soaring vast distances over the open seas. Due to its size, the bird is presumed to have been an excellently adapted dynamic soarer . It probably built its nest on high plateaus or similar places, where it could easily take flight by simply walking into
3108-667: Is a rather comprehensive fossil preserved mostly as imprint, with some bone pieces and even feather impressions in addition; it was found in Clarendonian ( Late Miocene ) shale of California (USA). Subsequently, for example in the Barstovian ( Middle Miocene ) Round Mountain Silt or in Late Miocene deposits of the Monterey Formation , quite a few additional specimens dating from about
3219-517: 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
3330-444: 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
3441-585: 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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3552-417: 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
3663-522: Is not from the Paleogene Atlantic region. It has been proposed as a monotypic genus Neodontornis , but this has not been widely accepted. It may be valid still, as the bones are of a rather small pseudotooth bird; though apparently too small for Osteodontornis detailed comparisons could be insightful. Its jugal arch is indeed short and very stout behind the orbital process of the prefrontal bone , like in Osteodontornis but apparently unlike in
3774-404: Is subdivided into five vertical regions. From the top down, these are: The illuminated zone at the surface of the sea with sufficient light for photosynthesis. Nearly all primary production in the ocean occurs here, and marine life is concentrated in this zone, including plankton , floating seaweed , jellyfish , tuna , many sharks and dolphins . The most abundant organisms thriving into
3885-592: 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
3996-490: Is the ecological region at the very bottom, including the sediment surface and some subsurface layers. Marine organisms such as clams and crabs living in this zone are called benthos . Just above the benthic zone is the demersal zone. Demersal fish can be divided into benthic fish , which are denser than water and rest on the bottom, and benthopelagic fish , which swim just above the bottom. Demersal fish are also known as bottom feeders and groundfish . The pelagic zone
4107-525: 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
4218-457: 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
4329-449: The Barstovian specimen LACM 50660 from Kern County, California ) can be compared to that of a smaller and older fossil tentatively assigned to Odontopteryx . Osteodontornis has a wider and deeper notch between the external condyle and the ectepicondylar prominence, with the pit between these farther from the bone's end, than did the smallish Paleogene species. Its quadrate bone differed from that of Odontopteryx toliapica in
4440-670: The Equatorial currents . Whether this also held true in the warmer climate of the Miocene is not known, but the general phylogenetic patterns found in Procellariiformes suggests that the north–south division is rather ancient and evolved even before the Miocene. From the Neogene of New Zealand "Pseudodontornis" stirtoni has been described, which unlike the rest of its (doubtfully valid) genus
4551-481: The Greek underworld . This is the deepest part of the ocean at more than 6,000 m (20,000 ft) or 6,500 m (21,300 ft), depending on authority. Such depths are generally located in trenches . The pelagic ecosystem is based on phytoplankton . Phytoplankton manufacture their own food using a process of photosynthesis . Because they need sunlight, they inhabit the upper, sunlit epipelagic zone, which includes
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4662-474: 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
4773-477: 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
4884-619: 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
4995-411: The hadopelagic . Coastal waters are generally the relatively shallow epipelagic. Altogether, the pelagic zone occupies 1,330 million km (320 million mi ) with a mean depth of 3.68 km (2.29 mi) and maximum depth of 11 km (6.8 mi). Pelagic life decreases as depth increases. The pelagic zone contrasts with the benthic and demersal zones at the bottom of the sea. The benthic zone
5106-410: 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
5217-484: 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,
5328-507: The type species of its supposed genus, P. longirostris . A larger proximal (initially misidentified as distal ) humerus piece ( CMNZ AV 24,960), probably from the Waiauan (Middle/Late Miocene) and found near the Waipara River mouth, is little if any distinct from O. orri in shape and size; it has a flange at the side and is less straight, but whether these features are natural or due to
5439-500: The water column of coastal, ocean, and lake waters, but not on or near the bottom of the sea or the lake. They can be contrasted with demersal fish, which do live on or near the bottom, and coral reef fish . Pelagic fish are often migratory forage fish , which feed on plankton , and the larger predatory fish that follow and feed on the forage fish. Examples of migratory forage fish are herring , anchovies , capelin , and menhaden . Examples of larger pelagic fish which prey on
5550-619: 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
5661-451: 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,
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#17330925317475772-605: 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
5883-558: The Miocene North American material was initially (and sometimes is still) assigned to Pelagornis , recent authors generally place them in the present genus. Some wing bone fossils from the Eo - Oligocene boundary of Oregon (United States), though assigned to Argillornis (= Dasornis ), do not differ much from those of Osteodontornis (as far as can be told in their fragmented state), and may be from an older relative. They are
5994-570: 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
6105-518: 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
6216-504: The United States government, to force the removal of Native Americans , many of whom relied on the bison for food. Pelagic The pelagic zone consists of the water column of the open ocean and can be further divided into regions by depth. The word pelagic is derived from Ancient Greek πέλαγος ( pélagos ) 'open sea'. The pelagic zone can be thought of as an imaginary cylinder or water column between
6327-429: 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
6438-753: The coastal or neritic zone . Biodiversity diminishes markedly in the deeper zones below the epipelagic zone as dissolved oxygen diminishes, water pressure increases, temperatures become colder, food sources become scarce, and light diminishes and finally disappears. Some examples of pelagic invertebrates include krill , copepods , jellyfish , decapod larvae , hyperiid amphipods , rotifers and cladocerans . Thorson's rule states that benthic marine invertebrates at low latitudes tend to produce large numbers of eggs developing to widely dispersing pelagic larvae, whereas at high latitudes such organisms tend to produce fewer and larger lecithotrophic (yolk-feeding) eggs and larger offspring. Pelagic fish live in
6549-600: 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
6660-418: 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
6771-583: The damaged state of the specimens is unclear. It also agrees more with Pelagornis than with Paleogene remains from Oregon mentioned above. A distal left humerus end and some wing bone fragments from the Late Oligocene Yamaga Formation of Kitakyūshū (Japan) might be the oldest remains of an Osteodontornis , but their assignment to the present genus is just as uncertain as in the case of the New Zealand fossil. Also from Japan are one or two of
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#17330925317476882-471: 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
6993-403: 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
7104-570: The entire genus (regardless of how many species can be recognized) may be a junior synonym of Cyphornis . Generally, recent authors have tended to place large Neogene pseudotooth bird fossils from the Atlantic in Pelagornis , and those from the North Pacific in Osteodontornis . It remains to be seen if this east–west division can be upheld, but biogeographically it seems quite sensible at least as
7215-575: 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
7326-443: 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
7437-475: 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
7548-533: 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
7659-462: The first years of their lives in the pelagic zone, moving closer to shore as they reach maturity. Pelagic birds , also called oceanic birds or seabirds , live on open seas and oceans rather than inland or around more restricted waters such as rivers and lakes. Pelagic birds feed on planktonic crustaceans , squid and forage fish . Examples are the Atlantic puffin , macaroni penguins , sooty terns , shearwaters , and Procellariiformes such as
7770-477: The forage fish are billfish , tuna , and oceanic sharks . Hydrophis platurus , the yellow-bellied sea snake, is the only one of the 65 species of marine snakes to spend its entire life in the pelagic zone. It bears live young at sea and is helpless on land. The species sometimes forms aggregations of thousands along slicks in surface waters. The yellow-bellied sea snake is the world's most widely distributed snake species. Many species of sea turtles spend
7881-435: 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
7992-580: 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
8103-660: 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
8214-447: 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
8325-475: 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
8436-557: The importance of the specimen. The bony-toothed or pseudotooth birds were initially believed to be related to albatrosses in the Procellariiformes , but actually they seem to be rather close relatives of either pelicans and storks , or of waterfowl , and are here placed in the order Odontopterygiformes to account for this uncertainty. Also, their internal taxonomy is not well-resolved. An earlier-described pseudotooth bird, Cyphornis magnus from Vancouver Island (Canada),
8547-431: 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,
8658-485: 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
8769-553: The mesopelagic zone are heterotrophic bacteria. Animals living in this zone include swordfish , squid , wolffish and some species of cuttlefish . Many organisms living here are bioluminescent . Some mesopelagic creatures rise to the epipelagic zone at night to feed. The name stems from Ancient Greek βαθύς 'deep'. The ocean is pitch black at this depth apart from occasional bioluminescent organisms, such as anglerfish . No plants live here. Most animals survive on detritus known as " marine snow " falling from
8880-421: 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
8991-532: The mysterious Pseudodontornis longirostris skull (which some consider to belong in Pelagornis ) is not very well preserved; it agees with Odontopteryx in a broad main shaft and with Osteodontornis in the straight main shaft ridge and its upward-directed ventral articulation ridge's forward center. Otherwise, it differs from both. This species is well documented from various locations of generally Miocene age, although usually by much fragmented remains due to
9102-490: 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
9213-469: 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
9324-410: 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
9435-431: The number of layers depending on the depth of the water. Marine life is affected by bathymetry (underwater topography) such as the seafloor, shoreline, or a submarine seamount , as well as by proximity to the boundary between the ocean and the atmosphere at the ocean surface, which brings light for photosynthesis, predation from above, and wind stirring up waves and setting currents in motion. The pelagic zone refers to
9546-488: The oldest known remains of large North Pacific pseudotooth birds, but if the enigmatic Cyphornis magnus from the same region dates back to the Paleogene they may well be assignable to that taxon , whatever their systematic affiliations might be beyond that. As few directly comparable bones of sufficient quality exist, the relationship of Osteodontornis to other pseudotooth birds is not completely resolved. As noted above,
9657-408: The open, free waters away from the shore, where marine life can swim freely in any direction unhindered by topographical constraints. The oceanic zone is the deep open ocean beyond the continental shelf , which contrasts with the inshore waters near the coast , such as in estuaries or on the continental shelf. Waters in the oceanic zone plunge to the depths of the abyssopelagic and further to
9768-399: 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
9879-702: 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
9990-410: 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
10101-734: The same age from the Mizunami Group at Mizunami, Gifu . From the Early Miocene Nye Formation and the Middle Miocene Astoria Formations of Oregon a handful of specimens that appear to be Osteodontornis are known. Similar fossils have been found in the Middle Miocene Capadare Formation of Venezuela and from the Late Miocene of the Pisco Formation of Peru ; they might rather be of
10212-701: The same time were found in California. Roughly contemporary specimens were described from the Haranoyan-Tozawan boundary in Japan – a complete right quadrate bone ( NSM PV-18696) from the Middle Miocene Nagura Formation at Chichibu, Saitama , an Early Miocene right mandible piece (Mizunami Fossil Museum (MFM) 28351) found in the Oi Formation at Misato, Mie , and some additional material of about
10323-457: The second-largest flying birds known, surpassed only by the teratorn Argentavis magnificens . The head, from neck to bill-tip, measured about 40 centimetres (1.3 ft), and the eyesockets were about 5.3 centimetres (2.1 in) wide. The humerus , though about as long as a human's, was only about 3.5 centimetres (1.4 in) wide at the shoulder end. The skull's quadrate bone measured almost 30 millimetres (1.2 in) at its widest and
10434-460: 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
10545-430: 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
10656-403: The surface of the sea and the bottom. Conditions in the water column change with depth: pressure increases; temperature and light decrease; salinity, oxygen, micronutrients (such as iron, magnesium and calcium) all change. In a manner analogous to stratification in the Earth's atmosphere , the water column can be divided vertically into up to five different layers (illustrated in the diagram), with
10767-503: The thin and tender bones it had. Most importantly, it was found on both sides of the North Pacific . It is not certain whether all Osteodontornis remains belong to a single species; size differences suggest that some evolution took place during the timespan in which the genus existed. Thus, some fossils are referred to Osteodontornis only, without further assigning them to this species. The type specimen of O. orri , SBMNH 309,
10878-412: 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
10989-555: 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
11100-422: The water in flight or while swimming. Lightly built as it was, O. orri was probably not a good diver and may have found it impossible to dive at all. Osteodontornis is one of the pseudotooth birds of which rather comprehensive remains are known, but the lack of good fossils of most other Odontopterygiformes allows for few direct comparisons between genera. Still, the distal humerus of the present genus (e.g.
11211-577: 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
11322-487: The wind with wings spread. It was a seabird that apparently lived mainly off squid and other soft-bodied prey; the "teeth" were less saw-like than the horny serrations on the beak of the fish-eating saw-billed ducks ( Merginae ), pointing straight downwards instead and in the fossils often very abraded or broken. The downward-pointing "teeth" were ideal for digging into and holding slippery, soft-skinned pelagic animals such as cephalopods that were probably snatched out of
11433-744: The youngest pseudodontorn fossils – a fragmentary right humerus from the Early Pliocene Yushima Formation at Maesawa , and probably also a distal right femur (MFM 1801) from the Early Pleistocene Dainichi Formation at Kakegawa that was initially believed to be from an albatross. These might represent the last survivors of Osteodontornis – the Kakegawa fossil at least is a good match in size –, but require more study before they can be assigned there. [REDACTED] [REDACTED] Extinct Extinction
11544-406: The zones above or, like the marine hatchetfish , by preying on other inhabitants of this zone. Other examples of this zone's inhabitants are giant squid , smaller squid and the grimpoteuthis or "dumbo octopus". The giant squid is hunted here by deep-diving sperm whales . The name is derived from Ancient Greek ἄβυσσος 'bottomless' - a holdover from times when the deep ocean
11655-508: Was believed to be of Eocene age but is nowadays assumed to have lived about twenty million years ago in the Early Miocene , not too long before the Clarendonian ( Middle / Late Miocene ) O. orri . It may be that Osteodontornis is a junior synonym of Cyphornis . With a wingspan of 5.5 to 6 metres (18 to 20 ft) and a height of 1.2 metres (3.9 ft) when on the ground, Osteodontornis orri and similar giant pseudotooth birds were
11766-410: Was believed to indeed be bottomless. Among the very few creatures living in the cold temperatures, high pressures and complete darkness here are several species of squid; echinoderms including the basket star , swimming cucumber, and the sea pig ; and marine arthropods including the sea spider . Many species at these depths are transparent and eyeless. The name is derived from the realm of Hades ,
11877-483: 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
11988-425: Was nearly 45 millimetres (1.8 in) high. Like its relatives, O. orri had a stout but extremely light-boned body, feet that were presumably webbed as in its aquatic relatives, and long and probably very narrow wings resembling those of an albatross . Its beak made up about three-quarters of the head's length and had bony tooth -like serrations that were hollow or maybe filled with cancellous bone . The beak
12099-430: 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
12210-571: 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
12321-409: Was so heavy the creature probably held it between its shoulders while in flight, just like modern pelicans do. The arrangement of its bony serrations is characteristic for this genus: one small "tooth", flanked by small points or even smaller "teeth", is placed between each pair of large ones. However, the "tooth" pattern of pseudotooth birds changed along the length of the beak, and is not considered
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