69°30′S 65°00′W / 69.500°S 65.000°W / -69.500; -65.000 The Antarctic Peninsula , known as O'Higgins Land in Chile and Tierra de San Martín in Argentina, and originally as Graham Land in the United Kingdom and the Palmer Peninsula in the United States, is the northernmost part of mainland Antarctica .
143-480: Antarcticeras is an extinct genus of enigmatic cephalopod from the Eocene of Antarctica . It contains a single species, A. nordenskjoeldi . It is either considered the last of the " orthocone "-type cephalopods, the only member of its subclass Paracoleoidea & a descendant of the orthoceratids , and a remarkable example of convergent evolution with coleoid cephalopods, or an oegospid squid and
286-438: 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
429-669: A nautilus to the Royal Society that was more than two feet in diameter, and morphologically distinct from any known living species. Hooke theorized that this was simply because the species lived in the deep ocean and no one had discovered them yet. While he contended that it was possible a species could be "lost", he thought this highly unlikely. Similarly, in 1695, Sir Thomas Molyneux published an account of enormous antlers found in Ireland that did not belong to any extant taxa in that area. Molyneux reasoned that they came from
572-415: 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
715-435: 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
858-422: A transitional form between the mineralized, functional phragomocones seen in certain coleoids and the fully demineralized gladius seen in oegopsid squid. For this reason, Antarcticeras was proposed as the first instance of a fossilized squid shell, which would also indicate that squid gladii had developed remarkably late in the evolutionary history of cephalopods. The late development of the modern squid gladius
1001-486: A transitional form in the development of the modern squid gladius , of which it is the only preserved example. It is named after Swedish geologist and Antarctic explorer Otto Nordenskjöld . Antarcticeras is represented by two fossil shell fragments from the Early Eocene La Meseta Formation from Seymour Island , Antarctica. These are straight shells that closely resemble those of
1144-436: 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
1287-479: A Lazarus species when extant individuals were described in 2019. Attenborough's long-beaked echidna ( Zaglossus attenboroughi ) is an example of a Lazarus species from Papua New Guinea that had last been sighted in 1962 and believed to be possibly extinct, until it was recorded again in November 2023. Some species currently thought to be extinct have had continued speculation that they may still exist, and in
1430-503: A cascade of coextinction across the trophic levels . Such effects are most severe in mutualistic and parasitic relationships. An example of coextinction is the Haast's eagle and the moa : the Haast's eagle was a predator that became extinct because its food source became extinct. The moa were several species of flightless birds that were a food source for the Haast's eagle. Extinction as
1573-429: A common ancestor with modern horses. Pseudoextinction is much easier to demonstrate for larger taxonomic groups. A Lazarus taxon or Lazarus species refers to instances where a species or taxon was thought to be extinct, but was later rediscovered. It can also refer to instances where large gaps in the fossil record of a taxon result in fossils reappearing much later, although the taxon may have ultimately become extinct at
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#17327938820631716-399: 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
1859-434: A funneling effect, which channels the winds into the relatively narrow Drake Passage . Hope Bay , at 63°23′S 057°00′W / 63.383°S 57.000°W / -63.383; -57.000 , is near the northern extremity of the peninsula, Prime Head , at 63°13′S. Near the tip at Hope Bay is Sheppard Point . The part of the peninsula extending northeastwards from a line connecting Cape Kater to Cape Longing
2002-708: 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
2145-405: 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
2288-607: A later point. The coelacanth , a fish related to lungfish and tetrapods , is an example of a Lazarus taxon that was known only from the fossil record and was considered to have been extinct since the end of the Cretaceous Period . In 1938, however, a living specimen was found off the Chalumna River (now Tyolomnqa) on the east coast of South Africa. Calliostoma bullatum , a species of deepwater sea snail originally described from fossils in 1844 proved to be
2431-581: A maritime Antarctic climate, is the mildest part of the Antarctic Peninsula. Within this part of the Antarctic Peninsula, temperatures exceed 0 °C (32 °F) for 3 or 4 months during the summer, and rarely fall below −10 °C (14 °F) during the winter. Farther south along the west coast and the northeast coast of the peninsula, mean monthly temperatures exceed 0 °C (32 °F) for only one or two months of summer and average around −15 °C (5 °F) in winter. The east coast of
2574-729: A marked increase in the number of research bases as Britain, Chile and Argentina competed to make claims over the same area. Meteorology and geology were the primary research subjects. Since the peninsula has the mildest climate in Antarctica, the highest concentration of research stations on the continent can be found there, or on the many nearby islands, and it is the part of Antarctica most often visited by tour vessels and yachts. Occupied bases include Base General Bernardo O'Higgins Riquelme , Bellingshausen Station , Carlini Base , Comandante Ferraz Antarctic Station , Palmer Station , Rothera Research Station , and San Martín Base . Today on
2717-594: A mathematical model that falls in all positions. By contrast, conservation biology uses the extinction vortex model to classify extinctions by cause. When concerns about human extinction have been raised, for example in Sir Martin Rees ' 2003 book Our Final Hour , those concerns lie with the effects of climate change or technological disaster. Human-driven extinction started as humans migrated out of Africa more than 60,000 years ago. Currently, environmental groups and some governments are concerned with
2860-456: 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
3003-441: 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,
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#17327938820633146-610: 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
3289-407: 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
3432-502: 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
3575-510: A reduction in atmospheric CO 2 concentrations. Initially, during the Eocene, this climate cooling resulted in a decrease in diversity of the angiosperm-dominated vegetation that inhabited the northern Antarctic Peninsula. During the Oligocene, about 34–23 Ma , these woodlands were replaced by a mosaic of southern beech ( Nothofagus ) and conifer-dominated woodlands and tundra as
3718-499: A result of climate change has been confirmed by fossil studies. Particularly, the extinction of amphibians during the Carboniferous Rainforest Collapse , 305 million years ago. A 2003 review across 14 biodiversity research centers predicted that, because of climate change, 15–37% of land species would be "committed to extinction" by 2050. The ecologically rich areas that would potentially suffer
3861-479: 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
4004-439: 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
4147-404: 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
4290-518: 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
4433-438: Is 35 cm (14 in) or less with occasional rain. Along the east coast of the Antarctic Peninsula south of 63° S, precipitation ranges from 10 to 15 cm (3.9 to 5.9 in). In comparison, the subantarctic islands have precipitation of 100–200 cm (39–79 in) per year and the dry interior of Antarctica is a virtual desert with only 10 cm (3.9 in) precipitation per year. The climate in and around
Antarcticeras - Misplaced Pages Continue
4576-564: Is a cormorant which is native to many sub-Antarctic islands, the Antarctic Peninsula and southern South America. Also present are the Antarctic petrel , Antarctic shag , king penguin , macaroni penguin , and Arctic tern . Although this very remote part of the world has never been inhabited and is protected by the Antarctic Treaty System , which bans industrial development, waste disposal and nuclear testing, there
4719-523: Is also evidence to suggest that this event was preceded by another mass extinction, known as Olson's Extinction . The Cretaceous–Paleogene extinction event (K–Pg) occurred 66 million years ago, at the end of the Cretaceous period; it is best known for having wiped out non-avian dinosaurs , among many other species. According to a 1998 survey of 400 biologists conducted by New York 's American Museum of Natural History , nearly 70% believed that
4862-577: Is an active volcano at the southern end of this rift zone. Notable fossil locations include the Late Jurassic to Early Cretaceous Fossil Bluff Group of Alexander Island , Early Cretaceous sediments in Byers Peninsula on Livingston Island , and the sediments on Seymour Island , which include the Cretaceous extinction . The peninsula is very mountainous, its highest peaks rising to about 2,800 m (9,200 ft). Notable peaks on
5005-444: 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
5148-681: Is called the Trinity Peninsula. Brown Bluff is a rare tuya and Sheppard Nunatak is found here also. The Airy , Seller , Fleming and Prospect Glaciers form the Forster Ice Piedmont along the west coast of the peninsula. Charlotte Bay , Hughes Bay and Marguerite Bay are all on the west coast as well. On the east coast is the Athene Glacier ; the Arctowski and Åkerlundh Nunataks are both just off
5291-585: 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
5434-417: 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
5577-697: Is evident in the Scotia Metamorphic Complex, which outcrops on Elephant Island , along with Clarence and Smith Islands of the South Shetland Islands . The Drake Passage opened about 30 Ma as Antarctica separated from South America. The South Shetland Island separated from Graham Land about 4 Ma as a volcanic rift formed within the Bransfield Strait . Three dormant submarine volcanoes along this rift include The Axe, Three Sisters, and Orca. Deception Island
5720-679: Is still a threat to these fragile ecosystems from increasing tourism, primarily on cruises across the Southern Ocean from the port of Ushuaia , Argentina . A rich record of fossil leaves, wood, pollen, and flowers demonstrates that flowering plants thrived in subtropical climates within the volcanic island arcs that occupied the Antarctic Peninsula region during the Cretaceous and very early Paleogene periods. The analysis of fossil leaves and flowers indicates that semitropical woodlands, which were composed of ancestors of plants that live in
5863-592: 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
Antarcticeras - Misplaced Pages Continue
6006-525: 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
6149-612: The Antarctic Circle , is the most northerly part of Antarctica, it has the mildest climates within this continent. Its climate is therefore classified as a tundra , rather than an ice cap . Its temperatures are warmest in January, averaging 1 to 2 °C (34 to 36 °F), and coldest in June, averages from −15 to −20 °C (5 to −4 °F). Its west coast from the tip of the Antarctic Peninsula south to 68° S , which has
6292-593: The Antarctic Peninsula ; however, reworking would not refute the idea of Antarcticeras forming a unique cephalopod lineage. In addition, a Late Devonian orthocone from Timan Ridge in Russia was found to closely resemble Antarcticeras in siphuncle placement, and was thus cited as a potential Paleozoic representative of the Paracoleoidea. Extinction Extinction is the termination of
6435-512: The Antarctic hair grass ( Deschampsia antarctica ) and Antarctic pearlwort ( Colobanthus quitensis ) are found on the northern and western parts of the Antarctic Peninsula, including offshore islands, where the climate is relatively mild. Lagotellerie Island in Marguerite Bay is an example of this habitat. Xanthoria elegans and Caloplaca are visible crustose lichens seen on coastal rocks. Antarctic krill are found in
6578-675: The Cretaceous to present times, and outcrops are found along the Gerlache Strait , the Lemaire Channel , Argentine Islands , and Adelaide Island . These rocks in western Graham Land include andesite lavas and granite from the magma , and indicate Graham Land was a continuation of the Andes . This line of volcanoes are associated with subduction of the Phoenix Plate . Metamorphism associated with this subduction
6721-675: The Gondwanaland supercontinent. Analysis of paleontologic, stratigraphic, and sedimentologic data acquired from the study of drill core and seismic acquired during the Shallow Drilling on the Antarctic Continental Shelf (SHALDRIL) and other projects and from fossil collections from and rock outcrops within Alexander, James Ross, King George, Seymour, and South Shetland Islands has yielded a record of
6864-483: The International Union for Conservation of Nature (IUCN) are not known to have any living specimens in the wild and are maintained only in zoos or other artificial environments. Some of these species are functionally extinct, as they are no longer part of their natural habitat and it is unlikely the species will ever be restored to the wild. When possible, modern zoological institutions try to maintain
7007-485: The Late Pleistocene could take up to 5 to 7 million years to restore mammal diversity to what it was before the human era. Extinction of a parent species where daughter species or subspecies are still extant is called pseudoextinction or phyletic extinction. Effectively, the old taxon vanishes, transformed ( anagenesis ) into a successor, or split into more than one ( cladogenesis ). Pseudoextinction
7150-564: The Swedish Antarctic Expedition , one of the first expeditions to explore parts of Antarctica. They landed on the Antarctic Peninsula in February 1902, aboard the ship Antarctic , which sank not far from the peninsula. All crew were rescued by an Argentine ship. The British Graham Land expedition between 1934 and 1937 carried out aerial surveys using a de Havilland Fox Moth aircraft, and concluded that Graham Land
7293-494: The United Kingdom . None of these claims have international recognition and, under the Antarctic Treaty System , the respective countries do not attempt to enforce their claims. The British claim, however, is recognised by Australia , France , New Zealand , and Norway . Argentina has the most bases and personnel stationed on the peninsula. The most likely first sighting of the Antarctic Peninsula, and therefore also of
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#17327938820637436-628: The dinosaur genus Antarctopelta , which was the first dinosaur fossil to be found on Antarctica. Paleogene and Early Eocene marine sediments that outcrop on Seymour Island contain plant-rich horizons. The fossil plants are dominated by permineralized branches of conifers and compressions of angiosperm leaves, and are found within carbonate concretions. These Seymour Island region fossils date to about 51.5–49.5 Ma and are dominated by leaves, cone scales, and leafy branches of Araucarian conifers, very similar in all respects to living Araucaria araucana (monkey puzzle) from Chile. They suggest that
7579-616: The fossil record ) after a period of apparent absence. More than 99% of all species that ever lived on Earth , amounting to over five billion species, are estimated to have died out. It is estimated that there are currently around 8.7 million species of eukaryotes globally, and possibly many times more if microorganisms , like bacteria , are included. Notable extinct animal species include non-avian dinosaurs , saber-toothed cats , dodos , mammoths , ground sloths , thylacines , trilobites , golden toads , and passenger pigeons . Through evolution , species arise through
7722-408: The killer whale . The animals of Antarctica live on food they find in the sea—not on land—and include seabirds , seals and penguins . The seals include: leopard seal ( Hydrurga leptonyx ), Weddell seal ( Leptonychotes weddellii ), the huge southern elephant seal ( Mirounga leonina ), and crabeater seal ( Lobodon carcinophagus ). Penguin species found on the peninsula, especially near
7865-440: The paleontology , sedimentology , stratigraphy , structural geology , and volcanology of glacial and nonglacial deposits of the Antarctic Peninsula has allowed the reconstruction of the paleoclimatology and prehistoric ice sheet fluctuation of it for over the last 100 million years. This research shows the dramatic changes in climate, which have occurred within this region after it reached its approximate position within
8008-410: 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
8151-488: The strata of the Paris basin. They saw alternating saltwater and freshwater deposits, as well as patterns of the appearance and disappearance of fossils throughout the record. From these patterns, Cuvier inferred historic cycles of catastrophic flooding, extinction, and repopulation of the earth with new species. Cuvier's fossil evidence showed that very different life forms existed in the past than those that exist today,
8294-639: The 20 biodiversity goals laid out by the Aichi Biodiversity Targets in 2010, only 6 were "partially achieved" by the deadline of 2020. The report warned that biodiversity will continue to decline if the status quo is not changed, in particular the "currently unsustainable patterns of production and consumption, population growth and technological developments". In a 2021 report published in the journal Frontiers in Conservation Science , some top scientists asserted that even if
8437-451: 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,
8580-805: The Antarctic Circle during the Cretaceous Period. The Fossil Bluff Group , which outcrops within Alexander Island , provides a detailed record, which includes paleosols and fossil plants, of Middle Cretaceous ( Albian ) terrestrial climates. The sediments that form the Fossil Bluff Group accumulated within a volcanic island arc , which now forms the bedrock backbone of the Antarctic Peninsula, in prehistoric floodplains and deltas and offshore as submarine fans and other marine sediments. As reflected in
8723-541: The Antarctic Peninsula consists of a string of bedrock islands; these are separated by deep channels whose bottoms lie at depths considerably below current sea level. They are joined by a grounded ice sheet. Tierra del Fuego , the southernmost tip of South America , is about 1,000 km (620 miles) away across the Drake Passage . The Antarctic Peninsula is 522,000 square kilometres (202,000 sq mi) in area and 80% ice-covered. The marine ecosystem around
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#17327938820638866-541: The Antarctic Peninsula formed as the bedrock islands underlying it were overridden and joined by an ice sheet in the early Pliocene about 5.3–3.6 Ma . During the Quaternary period, the size of the West Antarctic Ice Sheet has fluctuated in response to glacial–interglacial cycles. During glacial epochs, this ice sheet was significantly thicker than it is currently and extended to the edge of
9009-404: The Antarctic Peninsula is changing dramatically in 2024. The most recent temperature recorded was 10°C, which is higher than the peninsula region's average and deviates from the patterns of typical temperatures. The peninsula is getting very much affected by these sudden climate changes. In past years, researchers have seen northwesterly winds over the peninsula, and it is proven that this is one of
9152-685: The Antarctic Peninsula northward of a line between Cape Jeremy and Cape Agassiz ; and Palmer Land the part southward of that line, which is roughly 69° S. Palmer Land is named for the United States seal hunter Nathaniel Palmer . The Chilean name for the feature, O'Higgins Land, is in honor of Bernardo O'Higgins , the Chilean patriot and Antarctic visionary. Most other Spanish-speaking countries call it la Península Antártica , though Argentina also officially refers to this as Tierra de San Martín ; as of 2018 Argentina has more bases and personnel in
9295-448: The Antarctic Peninsula south of 63° S is generally much colder, with mean temperatures exceeding 0 °C (32 °F) for at most one month of summer, and winter mean temperatures ranging from −5 to −25 °C (23 to −13 °F). The colder temperatures of the southeast, Weddell Sea side, of the Antarctic Peninsula are reflected in the persistence of ice shelves that cling to the eastern side. Precipitation varies greatly within
9438-544: The Antarctic Peninsula there are many abandoned scientific and military bases. Argentina's Esperanza Base was the birthplace of Emilio Marcos Palma , the first person to be born in Antarctica. The grounding of the Argentine ship the ARA Bahía Paraíso and subsequent 170,000 US gal (640,000 L; 140,000 imp gal) oil spill occurred near the Antarctic Peninsula in 1989. Antarctica
9581-423: The Antarctic Peninsula. From the tip of the Antarctic Peninsula to 68° S, precipitation averages 35–50 cm (14–20 in) per year. A good portion of this precipitation falls as rain during the summer, on two-thirds of the days of the year, and with little seasonal variation in amounts. Between about 68° S and 63° S on the west coast of the Antarctic Peninsula and along its northeast coast, precipitation
9724-577: The Cretaceous thermal maximum the climate, both regionally and globally, appears to have cooled as seen in the Antarctic fossil wood record. Later, warm high-latitude climates returned to the Antarctic Peninsula region during the Paleocene and early Eocene as reflected in fossil plants. Abundant plant and marine fossils from Paleogene marine sediments that outcrop on Seymour Island indicate the presence of cool and moist, high-latitudes environment during
9867-618: The Earth is currently in the early stages of a human-caused mass extinction, known as the Holocene extinction . In that survey, the same proportion of respondents agreed with the prediction that up to 20% of all living populations could become extinct within 30 years (by 2028). A 2014 special edition of Science declared there is widespread consensus on the issue of human-driven mass species extinctions. A 2020 study published in PNAS stated that
10010-600: The Late Cretaceous ( Coniacian and Santonian -early Campanian ) strata of the Hidden Lake and Santa Maria formations, which outcrop within James Ross , Seymour , and adjacent islands, indicate that this emergent volcanic island arc enjoyed warm temperate or subtropical climates with adequate moisture for growth and without extended periods of below freezing winter temperatures. After the peak warmth of
10153-584: 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
10296-522: The Paris basin, could be formed by a slow rise and fall of sea levels . The concept of extinction was integral to Charles Darwin 's On the Origin of Species , with less fit lineages disappearing over time. For Darwin, extinction was a constant side effect of competition . Because of the wide reach of On the Origin of Species , it was widely accepted that extinction occurred gradually and evenly (a concept now referred to as background extinction ). It
10439-472: The United States government, to force the removal of Native Americans , many of whom relied on the bison for food. Antarctic Peninsula The Antarctic Peninsula is part of the larger peninsula of West Antarctica , protruding 1,300 km (810 miles) from a line between Cape Adams ( Weddell Sea ) and a point on the mainland south of the Eklund Islands . Beneath the ice sheet that covers it,
10582-429: 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
10725-511: The adjacent parts of the prehistoric Antarctic Peninsula were covered by forests that grew in a cool and moist, high-latitude environment during the early Eocene. During the Cenozoic climatic cooling, the Antarctic Peninsula was the last region of Antarctica to have been fully glaciated according to current research. As a result, this region was probably the last refugium for plants and animals that had inhabited Antarctica after it separated from
10868-437: The changes in terrestrial vegetation that occurred within the Antarctic Peninsula over the course of the past 37 million years. This research found that vegetation within the Antarctic Peninsula changed in response to a progressive climatic cooling that started with the initiation of mountain glaciation in the latest Eocene, about 37–34 Ma . The cooling was contemporaneous with glaciation elsewhere in Antarctica and
11011-407: The climate continued to cool. By middle Miocene, 16–11.6 Ma , a tundra landscape completely replaced any remaining woodlands. At this time, woodlands became completely extirpated from the Antarctic Peninsula and all of Antarctica. A tundra landscape probably persisted until about 12.8 Ma when the transition from a temperate, alpine glaciation to a dynamic ice sheet occurred. Eventually,
11154-409: The climate optimum, a distinct climate cooling, which lasted until historic times, occurred. The Antarctic Peninsula is a part of the world that is experiencing extraordinary warming. Each decade for the last five, average temperatures in the Antarctic Peninsula have risen by 0.5 °C (0.90 °F). Ice mass loss on the peninsula occurred at a rate of 60 billion tons / year in 2006, with
11297-600: 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
11440-418: 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
11583-620: The continental shelves. During interglacial epochs, the West Antarctica Ice Sheet was thinner than during glacial epochs and its margins lay significantly inland of the continental margins. During the Last Glacial Maximum , about 20,000 to 18,000 years ago, the ice sheet covering the Antarctic Peninsula was significantly thicker than it is now. Except for a few isolated nunataks , the Antarctic Peninsula and its associated islands were completely buried by
11726-476: The deliberate destruction of some species, such as dangerous viruses , and the total destruction of other problematic species has been suggested. Other species were deliberately driven to extinction, or nearly so, due to poaching or because they were "undesirable", or to push for other human agendas. One example was the near extinction of the American bison , which was nearly wiped out by mass hunts sanctioned by
11869-403: The early Cenozoic in the far southern latitudes, and the survival of orthocerid descendants into the Cenozoic. Later that year, The Guardian ranked Antarcticeras as one of the top fossil discoveries of 2017. In 2018, Fuchs et al published a study refuting the previous classification of Antarcticeras as a new subclass of cephalopods. The poorly mineralized phragmocone was recovered as
12012-474: The early Eocene. Detailed studies of the paleontology, sedimentology, and stratigraphy of glacial and nonglacial deposits within the Antarctic Peninsula and adjacent parts of the Weddell Sea and its Pacific continental shelf have found that it has become progressively glaciated as the climate of Antarctica dramatically and progressively cooled during the last 37 million years. This progressive cooling
12155-504: The east coast. A number of smaller peninsulas extend from the main Antarctic Peninsula, including Hollick-Kenyon Peninsula and Prehn Peninsula at the base of the Antarctic Peninsula. Also located here are the Scaife Mountains . The Eternity Range is found in the middle of the peninsula. Other geographical features include Avery Plateau , the twin towers of Una Peaks . Because the Antarctic Peninsula, which reaches north of
12298-558: The emergent parts of the volcanic island arc, the eroded roots of which now form the central part of the Antarctic Peninsula, were covered by either warm temperate or subtropical forests. These fossil plants are indicative of tropical and subtropical forest at high paleolatitudes during the Middle and Late Cretaceous, which grew in climates without extended periods of below freezing winter temperatures and with adequate moisture for growth. The Cretaceous strata of James Ross Island also yielded
12441-403: 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
12584-591: The event of rediscovery would be considered Lazarus species. Examples include the thylacine , or Tasmanian tiger ( Thylacinus cynocephalus ), the last known example of which died in Hobart Zoo in Tasmania in 1936; the Japanese wolf ( Canis lupus hodophilax ), last sighted over 100 years ago; the American ivory-billed woodpecker ( Campephilus principalis ), with the last universally accepted sighting in 1944; and
12727-443: 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
12870-475: 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
13013-540: The field of zoology , and biology in general, and has also become an area of concern outside the scientific community. A number of organizations, such as the Worldwide Fund for Nature , have been created with the goal of preserving species from extinction. Governments have attempted, through enacting laws, to avoid habitat destruction, agricultural over-harvesting, and pollution . While many human-caused extinctions have been accidental, humans have also engaged in
13156-435: 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
13299-572: The greatest change occurring in the northern tip of the peninsula. Seven ice shelves along the Antarctic Peninsula have retreated or disintegrated in the last two decades. Research by the United States Geological Survey has revealed that every ice front on the southern half of the peninsula experienced a retreat between 1947 and 2009. According to a study by the British Antarctic Survey , glaciers on
13442-580: 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
13585-676: The heaviest losses include the Cape Floristic Region and the Caribbean Basin . These areas might see a doubling of present carbon dioxide levels and rising temperatures that could eliminate 56,000 plant and 3,700 animal species. Climate change has also been found to be a factor in habitat loss and desertification . Studies of fossils following species from the time they evolved to their extinction show that species with high sexual dimorphism , especially characteristics in males that are used to compete for mating, are at
13728-447: 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
13871-475: 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
14014-494: The ice sheet from the Pacific outer continental shelf and the continental margin within the Weddell Sea. Within the Weddell Sea, the transition from grounded ice to a floating ice shelf occurred about 10,000 years ago. The deglaciation of some locations within the Antarctic Peninsula continued until 4,000 to 3,000 years ago. Within the Antarctic Peninsula, an interglacial climatic optimum occurred about 3,000 to 5,000 years ago. After
14157-474: The ice sheet is melting nonstop. Because of issues concerning global climate change, the Antarctic Peninsula and adjacent parts of the Weddell Sea and its Pacific continental shelf have been the subject of intensive geologic, paleontologic, and paleoclimatic research by interdisciplinary and multinational groups over the last several decades. The combined study of the glaciology of its ice sheet and
14300-438: The ice sheet. In addition, the ice sheet extended past the present shoreline onto the Pacific outer continental shelf and completely filled the Weddell Sea up to the continental margin with grounded ice. The deglaciation of the Antarctic Peninsula largely occurred between 18,000 and 6,000 years ago as an interglacial climate was established in the region. It initially started about 18,000 to 14,000 years ago with retreat of
14443-431: 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,
14586-604: The land by pack ice . Separating the peninsula from nearby islands are the Antarctic Sound , Erebus and Terror Gulf , George VI Sound , Gerlache Strait and the Lemaire Channel . The Lemaire Channel is a popular destination for tourist cruise ships that visit Antarctica. Further to the west lies the Bellingshausen Sea and in the north is the Scotia Sea . The Antarctic Peninsula and Cape Horn create
14729-488: The main drivers of the modern extinction crisis. In January 2020, the UN's Convention on Biological Diversity drafted a plan to mitigate the contemporary extinction crisis by establishing a deadline of 2030 to protect 30% of the Earth's land and oceans and reduce pollution by 50%, with the goal of allowing for the restoration of ecosystems by 2050. The 2020 United Nations ' Global Biodiversity Outlook report stated that of
14872-421: 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
15015-616: The most common on the Antarctic Peninsula are the chinstrap and gentoo, with the only breeding colony of emperor penguins in West Antarctica an isolated population on the Dion Islands , in Marguerite Bay on the west coast of the peninsula. Most emperor penguins breed in East Antarctica. Seabirds of the Southern Ocean and West Antarctica found on the peninsula include: southern fulmar ( Fulmarus glacialoides ),
15158-490: 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
15301-469: 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
15444-410: 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
15587-399: 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
15730-415: The orthocones, although they are thought to have been internal akin to those of certain coleoids such as the cuttlebone of cuttlefish and the "rams horn" shell of spirulids . The shells are weakly mineralized with the presence of soft tissues and were likely only preserved due to a unique depositional environment. Sympatric cephalopod taxa include the coiled nautiloid Euciphoceras . Antarcticeras
15873-494: The peninsula are not only retreating but also increasing their flow rate as a result of increased buoyancy in the lower parts of the glaciers. Professor David Vaughan has described the disintegration of the Wilkins Ice Shelf as the latest evidence of rapid warming in the area. The Intergovernmental Panel on Climate Change has been unable to determine the greatest potential effect on sea level rise that glaciers in
16016-402: The peninsula include Deschanel Peak , Mounts Castro , Coman , Gilbert , Jackson , William , Owen , Scott , and Hope , which is the highest point at 3,239 m (10,627 ft), Mount William , Mount Owen and Mount Scott . These mountains are considered to be a continuation of the Andes of South America , with a submarine spine or ridge connecting the two. This is the basis for
16159-552: The peninsula is typical Antarctic tundra . The peninsula has a sharp elevation gradient, with glaciers flowing into the Larsen Ice Shelf , which experienced significant breakup in 2002. Other ice shelves on the peninsula include the George VI , Wilkins , Wordie and Bach Ice Shelves . The Filchner-Ronne Ice Shelf lies to the east of the peninsula. Islands along the peninsula are mostly ice-covered and connected to
16302-466: The peninsula than any other nation. Other portions of the peninsula are named by and after the various expeditions that discovered them, including the Bowman , Black , Danco , Davis , English , Fallières , Nordenskjöld , Loubet , and Wilkins Coasts . The first Antarctic research stations were established during World War II by a British military operation, Operation Tabarin . The 1950s saw
16445-401: The plant fossils, paleosols, and climate models, the climate was warm, humid, and seasonally dry. According to climate models, the summers were dry and winters were wet. The rivers were perennial and subject to intermittent flooding as the result of heavy rainfall. Warm high-latitude climates reached a peak during the mid-Late Cretaceous Cretaceous Thermal Maximum . Plant fossils found within
16588-479: The position advanced by Chile and Argentina for their territorial claims. The Scotia Arc is the island arc system that links the mountains of the Antarctic Peninsula to those of Tierra del Fuego . There are various volcanoes in the islands around the Antarctic Peninsula. This volcanism is related to extensional tectonics in Bransfield Rift to the west and Larsen Rift to the east. The landscape of
16731-609: The presence of siphuncles and septa in Antarcticeras and the lack of these traits in modern oegopsids, and found the shell morphology of Antarcticeras to be unique among cephalopods, concluding that it was impossible of Antarcticeras to be a squid. The potential for Antarcticeras to be a reworked specimen was found to be unlikely due the lack of reworked material in the formation and the two specimens being found at different levels, although not impossible as fossil orthocones are known from Paleozoic formations in other parts of
16874-702: 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
17017-461: The reasons for the peninsula constantly melting and snow sublimation in 2024. Researchers are observing similar situations in 2024. Melting events have been observed on the eastern and western sides of the Peninsula in February and March. All three are contributing to the melting of ice in several Antarctic Peninsula areas, such as Larsen C and B. Furthermore, data from NASA's research indicates that
17160-516: The region may cause. The coasts of the peninsula have the mildest climate in Antarctica and moss and lichen -covered rocks are free of snow during the summer months, although the weather is still intensely cold and the growing season very short. The plant life today is mainly mosses, lichens and algae adapted to this harsh environment, with lichens preferring the wetter areas of the rocky landscape. The most common lichens are Usnea and Bryoria species. Antarctica's two flowering plant species,
17303-410: 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
17446-465: The scavenging southern giant petrel ( Macronectes giganteus ), Cape petrel ( Daption capense ), snow petrel ( Pagodroma nivea ), the small Wilson's storm-petrel ( Oceanites oceanicus ), imperial shag ( Phalacrocorax atriceps ), snowy sheathbill ( Chionis alba ), the large south polar skua ( Catharacta maccormicki ), brown skua ( Catharacta lönnbergi ), kelp gull ( Larus dominicanus ), and Antarctic tern ( Sterna vittata ). The imperial shag
17589-432: The seas surrounding the peninsula and the rest of the continent. The crabeater seal spends most of its life in the same waters feeding on krill. Bald notothen is a cryopelagic fish that lives in sub-zero water temperatures around the peninsula. Vocalizations of the sei whale can be heard emanating from the waters surrounding the Antarctic Peninsula. Whales include the Antarctic minke whale , dwarf minke whale , and
17732-460: 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
17875-399: The spread of moss, alterations in phytoplankton and zooplankton community composition as well as changes in krill recruitment, abundance and availability to predators. The Antarctic Peninsula is currently dotted with numerous research stations, and nations have made multiple claims of sovereignty . The peninsula is part of disputed and overlapping claims by Argentina , Chile , and
18018-430: 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
18161-412: 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
18304-465: The tip and surrounding islands, include the chinstrap penguin , emperor penguin , gentoo penguin and the Adélie penguin . Petermann Island is the world's southernmost colony of gentoo penguins. The exposed rocks on the island is one of many locations on the peninsula that provides a good habitat for rookeries . The penguins return each year and may reach populations of more than ten thousand. Of these
18447-567: The total extinction of the dodo and the extirpation of indigenous horses to the British Isles. He similarly argued against mass extinctions , believing that any extinction must be a gradual process. Lyell also showed that Cuvier's original interpretation of the Parisian strata was incorrect. Instead of the catastrophic floods inferred by Cuvier, Lyell demonstrated that patterns of saltwater and freshwater deposits , like those seen in
18590-938: The tropics today, thrived within this region during a global thermal maximum with summer temperatures that averaged 20 °C (68 °F). The oldest fossil plants come from the middle Cretaceous (Albian) Fossil Bluff Group, which outcrop along the edge of Alexander Island. These fossils reveal that at this time the forests consisted of large conifers , with mosses and ferns in the undergrowth. The paleosols, in which trees are rooted, have physical characteristics indicative of modern soils that form under seasonally dry climates with periodic high rainfall. Younger Cretaceous strata, which outcrop within James Ross, Seymour, and adjacent islands, contain fossil plants of Late Cretaceous angiosperms with leaf morphotypes that are similar to those of living families such as Sterculiaceae, Lauraceae, Winteraceae, Cunoniaceae, and Myrtaceae. They indicate that
18733-596: The western continental shelf of the Antarctic Peninsula (WAP) has been subjected to rapid climate change . Over the past 50 years, the warm, moist maritime climate of the northern WAP has shifted south. This climatic change increasingly displaces the once dominant cold, dry continental Antarctic climate. This regional warming has caused multi-level responses in the marine ecosystem such as increased heat transport , decreased sea ice extent and duration, local declines in ice-dependent Adélie penguins , increase in ice-tolerant gentoo and chinstrap penguins, accelerated greening due to
18876-503: The whole Antarctic mainland, was on 27 January 1820 by an expedition of the Imperial Russian Navy led by Fabian Gottlieb von Bellingshausen . But the party did not recognize as the mainland what they thought was an icefield covered by small hillocks. Three days later, on 30 January 1820, Edward Bransfield and William Smith , with a British expedition, were the first to chart part of the Antarctic Peninsula. This area
19019-581: The wider scientific community of his theory. Cuvier was a well-regarded geologist, lauded for his ability to reconstruct the anatomy of an unknown species from a few fragments of bone. His primary evidence for extinction came from mammoth skulls found in the Paris basin . Cuvier recognized them as distinct from any known living species of elephant, and argued that it was highly unlikely such an enormous animal would go undiscovered. In 1812, Cuvier, along with Alexandre Brongniart and Geoffroy Saint-Hilaire , mapped
19162-478: Was also found to support previous hypotheses of a Late Cretaceous origin for most extant decapodiform groups and a Cenozoic origin for modern squid, contrasting with other studies that had placed these divergences during the Paleozoic. It was also not ruled out that Antarcticeras may represent a fossil reworked from older geologic layers. Later in 2018, Doguzhaeva published a rebuttal to Fuchs et al , noting
19305-442: Was contemporaneous with a reduction in atmospheric CO 2 concentrations. During this climatic cooling, the Antarctic Peninsula was probably the last region of Antarctica to have been fully glaciated . Within the Antarctic Peninsula, mountain glaciation was initiated during the latest Eocene, about 37–34 Ma . The transition from temperate, alpine glaciation to a dynamic ice sheet occurred about 12.8 Ma . At this time,
19448-623: Was described in 2017 by Doguzhaeva et al ., who recovered it as the only member of a ghost lineage of cephalopods that had diverged from all others during the Paleozoic . Its coleoid-esque internal shell was recovered as an instance of convergent evolution with coleoids. The coleoids are thought to have originated within the Bactritida during the Late Paleozoic and share similar anatomical features with one another, but Antarcticeras
19591-491: Was difficult to disprove. When parts of the world had not been thoroughly examined and charted, scientists could not rule out that animals found only in the fossil record were not simply "hiding" in unexplored regions of the Earth. Georges Cuvier is credited with establishing the modern conception of extinction in a 1796 lecture to the French Institute , though he would spend most of his career trying to convince
19734-638: Was found to differ from both groups, with its siphuncle placement more closely resembling that of the Actinocerida and especially the Orthocerida , which were recovered as its potential ancestors. For this reason, it was classified within the new subclass Paracoleoidea , order Antarcticerida , and family Antarcticeratidae . This taxonomic placement would suggest the existence of an extremely ancient, previously unknown cephalopod lineage that had survived through several mass extinction events well into
19877-594: Was later to be called Trinity Peninsula and is the extreme northeast portion of the peninsula. The next confirmed sighting was in 1832 by John Biscoe , a British explorer, who named the northern part of the Antarctic Peninsula as Graham Land . The first European to land on the continent is also disputed. A 19th-century seal hunter , John Davis , was almost certainly the first. But, sealers were secretive about their movements and their logbooks were deliberately unreliable, to protect any new sealing grounds from competition. Between 1901 and 1904, Otto Nordenskjöld led
20020-526: Was not an archipelago but a peninsula. Agreement on the name "Antarctic Peninsula" by the Advisory Committee on Antarctic Names and UK Antarctic Place-Names Committee in 1964 resolved a long-standing difference over the use of the United States' name "Palmer Peninsula" or the British name "Graham Land" for this geographic feature. This dispute was resolved by making Graham Land the part of
20163-430: 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
20306-814: Was once part of the Gondwana supercontinent . Outcrops from this time include Ordovician and Devonian granites and gneiss found in the Scar Inlet and Joerg Peninsula , while the Carboniferous - Triassic Trinity Peninsula Group are sedimentary rocks that outcrop in Hope Bay and Prince Gustav Channel . Ring of Fire volcanic rocks erupted in the Jurassic , with the breakup of Gondwana, and outcrop in eastern Graham Land as volcanic ash deposits. Volcanism along western Graham Land dates from
20449-571: 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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