134-424: Niolamia is an extinct genus of South American meiolaniid turtle with a long and complex history. Like its relatives, Niolamia was a robust and heavily armored terrestrial turtle with large, horn like scales covering its head and a tail encased by rings of bone. This heavily armored build may have served the animal during intraspecific combat during courtship , though such encounters likely did not involve
268-438: 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
402-524: A holotype , didn't diagnose the species or even figured the fossil material. The imprecise information was not an accident, but the result of the rivalry between Ameghino and Moreno. Their rivalry, similar to the Bone Wars between Edward Drinker Cope and Othniel Charles Marsh in America, saw the two intentionally hide records from one another, eventually leading to the complete loss of some information. Around
536-657: 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
670-415: 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
804-436: 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
938-474: 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
1072-495: 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
1206-429: 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
1340-447: A display ritual may have incorporated different ritualized movements of the head based on the range of motion observed from the more recent Meiolania . Nevertheless, this does not rule out other aggressive behavior that was speculated upon in prior studies, with Degrange and colleagues specifically highlighting the animal's ability to bite. Though a directly defensive function of the frill is also deemed unlikely, it may have still served as
1474-399: 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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#17330845488381608-467: A follow-up expedition, which recovered additional remains in the form of a carapace, skull and associated mandible. That same year Argentinian paleontologist Florentino Ameghino coined the name Niolamia argentina for a skull he claimed his brother Carlos discovered in the Guaranitic Formation . However, little information was given by Ameghino at the time, as the researcher didn't established
1742-708: 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
1876-405: 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
2010-592: 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
2144-587: 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
2278-456: 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
2412-441: 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,
2546-610: 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
2680-646: A profound study of palaeontology, particularly of vertebrates,' in 1962. In 1966, Simpson received the Golden Plate Award of the American Academy of Achievement . At the University of Arizona , Tucson , the Gould-Simpson Building was named in honor of Simpson and Minnesota geologist and polar explorer Lawrence M. Gould , who, like Simpson, also accepted an appointment as Professor of Geosciences at
2814-407: 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
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#17330845488382948-502: 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
3082-486: 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
3216-479: 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
3350-439: 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
3484-404: 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
3618-518: 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
3752-471: A visual deterent when dealing with predators. Comparison between the neotype of Niolamia and AMNH 3161, formerly the holotype of Crossochelys and now considered to be a juvenile Niolamia , makes it possible to identify several changes the animal underwent in the process of reaching adulthood. AMNH 3161 represents a very young individual, less than a fourth the size of the Niolamia neotype skull. Accordingly,
3886-401: A way that makes them unsuited for headbutting, with the frill in particular being angled so that would make direct contact with the frill of a rival impossible. Additional points against headbutting can be found in the absence of pathologies on the holotype of Niolamia and the fact that meiolaniids as a whole have highly ankylosed skulls, meaning the shock of an impact could not be absorbed by
4020-517: 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
4154-469: Is also seen in Meiolania platyceps and modern tortoises of the family Testudinidae . Overall, the anatomy of the shoulder blade has been taken to indicate a terrestrial lifestyle due to its similarity with modern tortoises. While no complete shell of Niolamia is known, researchers were nonetheless able to determine several aspects of its shape. Although the largest fossils of the shell are flattened, this
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4288-444: 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
4422-400: Is believed to have been caused by taphonomy , crushing the bone during preservation. Instead, it is suggested that Niolamia had a domed shell like modern tortoises, a hypothesis in part based on the angle between the dorsal process and the acromion of the shoulder blade, which resembles modern testudinids. The shell appears to be thickest towards the borders and thinnest towards the midline of
4556-585: 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
4690-797: 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 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
4824-453: Is elongated, which today is only seen in turtles with snorkel like noses such as the mata mata , pig-nosed turtle and softshell turtles . Like other meiolaniids, the skull of Niolamia was covered in a multitude of horn or boss-like scales readily identifiable in the fossil material. These scales were described with varying nomenclature by different authors, with Woodward assigning them the numerals I - VII, while Simpson assigned letters to
4958-417: 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
5092-420: Is even greater than in extant terrestrial turtles, which in turn have a greater nasal cavity than aquatic species. Although the possibility that the dorsal region of the nasal cavity could have aided in vocalisation or thermoregulation, based on comparison to ornithischian dinosaurs, is not dismissed outright, it is considered relatively unlikely given the much more simple structure in meiolaniids. Leaving aside
5226-563: Is found in the Eocene to Miocene Sarmiento Formation. This is supported by the discovery of additional Niolamia fossils (initially described as Crossochelys ) from the Sarmiento Formation. Subsequently, later research favors the hypothesis that these turtles lived during the Eocene. The best preserved fossil of Niolamia is a nearly completely preserved skull, which is the most diagnostic element in meiolaniid turtles. Like in its relatives,
5360-409: Is not clear if this actually represents how it appeared in life or if this was simply the result of distortion after the animals death. The E scales are small elements restricted to the side of the skull, just before the tympanic cavity. They are convex and form small, backward directed bosses. The H scales seen in derived meiolaniids appear to be missing in Niolamia . The F scales cover the region above
5494-520: Is primarily distributed throughout the Neogene and Quaternary of Australasia , this makes Niolamia an important piece in the evolutionary history and origin of this turtle family. Remains attributed to Niolamia were seemingly first uncovered by Santiago Roth in 1889, with a well preserved skull found only shortly afterwards. The name Niolamia was however not coined by Roth or any of his contacts, but by Florentino Ameghino who briefly wrote about what
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5628-410: Is rather conservative and more in-line with what is seen in terrestrial turtles, which have a wide angle between the anterior and posterior semicircular canals . In modern tortoises this angle is approximately 100°, in more aquatic turtles like geoemydids and plesiochelydids 80-95° and in meiolaniids up to 115°. In terrestrial species, this wide angle between the semicircular canals servers to improve
5762-418: Is simply a younger Niolamia individual, with the distinguishing features simply representing individual variation or traits that would change with age. In a later publication, Sterli would further comment on the complex history of this taxon and the impact of the intense rivalry between Ameghino and Moreno on the history of Niolamia . According to Sterli, this competition may explain the whereabouts or rather
5896-592: 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
6030-525: 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
6164-530: Is unknown. The carapace length of Niolamia has been estimated based on comparison between shell fragments and the general proportions of the related Meiolania as well as those of the stem-turtle Proganochelys . The result yielded an estimated shell length of 1.2 m (3 ft 11 in) for Niolamia , however this estimate is not a certain one due to the fact that only fragmentary shell remains were known. Subsequently, future discoveries could confirm or contradict these results. Like in other meiolaniids,
6298-660: The American Museum of Natural History from 1945 to 1959. He was Curator of the Museum of Comparative Zoology at Harvard University from 1959 to 1970, and a Professor of Geosciences at the University of Arizona from 1968 until his retirement in 1982. Simpson was elected to the American Philosophical Society in 1936 and the United States National Academy of Sciences in 1941. In 1943 Simpson
6432-474: 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
6566-564: The La Plata Museum specifying the Cañadón Blanco locality. However the mammal fauna of said locality is more in line with an Eocene to Oligocene age, which matches Ameghino's claim that Roth's material stems from Middle Eocene strata near Lake Musters and Lake Colhué Huapí . Analysis of the sediments present in the neotype's nasal cavity revealed it to be white tuff , very much unlike the sediments described by Woodward and similar to what
6700-477: 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
6834-516: The paleobiogeography of meiolaniid turtles due to its presence in Neogene South America. In contrast to Niolamia , most other members of the family were endemic to Neogene to Quaternary Australasia, including Warkalania , Ninjemys , Meiolania and a variety of unnamed forms. For over 100 years Niolamia was the only form found outside this region until the discovery of Gaffneylania . The presence of these two genera marks them as part of
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#17330845488386968-410: 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
7102-484: 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,
7236-619: 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
7370-451: 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,
7504-468: The Austral biogeogeographical kingdom, which includes southern South America , Antarctica , south Africa , Australia , Tasmania , New Zealand and New Guinea . Animals of this biogeographical kingdom were heavily affected by the breakup of Gondwana in their distribution, with Antarctica in particular serving as a connective bridge between the fauna of South America and Australasia. Meiolaniids derive from
7638-405: The B scales and are the smallest of the three elements, as is typical for turtles of this family. They extend outward and down, covering part of the skullroof and the side of the skull while overhanging the tympanic cavity . A striking feature that sets this turtle apart from its relatives is the size of the X scale. The X scale is a singular scale that is situated along the midline of the skull atop
7772-605: 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
7906-547: The Eocene parts of the Sarmiento Formation (then named the Casamayor Formation), which they named Crossochelys corniger . Although Simpson argued that the material of Crossochelys was not that of a juvenile, Eugene S. Gaffney reasoned for the contrary in his 1996 review of meiolaniids, declaring Crossochelys a junior synonym of Niolamia . While meiolaniid research received a considerable boost under Gaffney,
8040-531: The Eocene-Oligocene, by which point the South American meiolaniids had not only dispersed into Patagonia but already gone extinct. The cause of the extinction of Niolamia and other South American meiolaniids was likely the gradually cooling and drying climate of middle Eocene Patagonia. Few studies directly deal with the specifics of Niolamia' s lifestyle. One exception to this is a 2017 study dealing with
8174-570: 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
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#17330845488388308-518: 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
8442-621: The United States government, to force the removal of Native Americans , many of whom relied on the bison for food. George Gaylord Simpson George Gaylord Simpson (June 16, 1902 – October 6, 1984) was an American paleontologist . Simpson was perhaps the most influential paleontologist of the twentieth century, and a major participant in the modern synthesis , contributing Tempo and Mode in Evolution (1944), The Meaning of Evolution (1949) and The Major Features of Evolution (1953). He
8576-509: The absence of Ameghino's fossil, which had seemingly disappeared from research history following the initial short description. No subsequent authors figured, described or even compared the Ameghino skull to the Roth skull. Juliana Sterli offers two possible explanations for this. It is possible that Ameghino's skull was simply lost, however it is likewise a possibility that the Ameghino and Roth skulls are
8710-429: 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
8844-600: 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
8978-418: 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
9112-471: 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
9246-416: The elongated vestibulum helps the animal to keep its nose free of sand, which may also occur during digging. However, the authors do not settle on a specific hypothesis and instead offer a variety of alternative ideas. These include an enhanced sense of smell, thermoregulation or even the production of sound. An enhanced sense of smell is also supported by the size of the nasal cavity (cavum nasi proprium). It
9380-403: 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
9514-421: The enhanced sense of smell and the anatomy of the inner ear support the idea that Niolamia was a terrestrial animal like modern tortoises. This is the most commonly inferred lifestyle for meiolaniid turtles and generally favoured over the aquatic model, which is occasionally suggested but not widely accepted. The potential use of the horns and frill has been a frequently considered but rarely studied matter, with
9648-575: 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
9782-443: 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
9916-475: 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
10050-399: The eye sockets, and the K and J scales the side of the skull from its back up to the beak region. The beak itself is covered by scale I, which can be divided into scale I1 and scale I2 in Niolamia . This region was likely covered by an extension of the rhamphotheca that covers the cutting surface turtles have in place of teeth. While the lower half of the snout tip is made up by the I scales,
10184-533: 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
10318-421: The first place and also misspelled Meiolania in his prior work. The naming issue was somewhat resolved when George Gaylord Simpson and Coleman S. Williams established Roth's material as the neotype of Niolamia in 1938, reasoning that Ameghino's material was not described thoroughly enough to serve as the holotype. In the same paper the researchers also officially described additional meiolaniid remains from
10452-435: 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
10586-444: The fossils of Niolamia remained in storage and publications released during this time were primarily based on the work of Woodward, rather than first hand observation of the skull. The convoluted history and poor description of the early meiolaniid discoveries of South America eventually led to a full redescription of the neotype in 2011, authored by Juliana Sterli and Marcelo de la Fuente. Like Gaffney, they too argue that Crossochelys
10720-427: The frill and sideways stabs. Given the large amounts of stress caused by the latter two actions, such behavior was generally deemed unlikely. This means that although the frill would be large enough to protect the neck, it's unlikely to have been used that way given the stresses of caudal torsion that would affect the bone in such a scenario. Though impacts using the forehead are less stressfull and Niolamia does share
10854-505: The genus apart from later taxa like Ninjemys and Meiolania , in which the internal nares are partially or fully divided by a bony septum . Above the nares, the nasal bone forms a small projection that extends beyond the end of the premaxillae , however this is nowhere near as well developed as in Ninjemys . The endocranium of Niolamia is dominated by the nasal cavity , which makes up approximately 60% of its volume. The vestibulum nasi
10988-580: 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
11122-660: 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
11256-447: 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
11390-421: The horns and frill, which are thought to serve more of a display function. Scans of the skull reveal that Niolamia likely had a great sense of smell but only low frequency hearing, indicating that these animals communicated more through chemical signals and smells than through sound. Niolamia is one of only two named meiolaniid turtles from South America, the other being Gaffneylania . Given that this family
11524-475: 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
11658-434: The individual scales. From Simpson's work, Gaffney refined and altered the nomenclature, which has since then become the standard nomenclature for the scale areas and horns of meiolaniid turtles. Most scales on the skull of Niolamia appear in pairs, the exception being scale A, X, Y and Z. Scale A in particular is part of the series of scales that form large horns and bosses along the back of the skull in all meiolaniids. While
11792-431: 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,
11926-439: The keen sense of smell inferred for them. Furthermore, chemical cues are associated with combat and aggression between modern turtles, especially during courtship , which may entail various shell-based maneuvers. This is congruent with prior studies suggesting a combat function for the highly armored bodies of meiolaniid turtles, which feature differently shaped osteoderms and armored tails. The inner ear of Niolamia meanwhile
12060-967: The later, as its position within the family is uncertain, being placed either alongside the derived Australasian forms or in a basal polytomy with Niolamia . The two phylogenetic trees below, after Gaffney, Archer & White and Sterli, de la Fuenta & Krause respectively, show the internal relationship of meiolaniids following the description of the two most recently named genera. Niolamia argentina Ninjemys oweni Warkalania carinaminor Meiolania brevicollis Meiolania platyceps Meiolania sp. Meiolania mackayi Crown Testudines Chubutemys copelloi Mongolochelys efremovi Peligrochelys walshae Otwayemys cunicularius Kallokibotion bajazidi Niolamia argentina Gaffneylania auricularis ? Ninjemys oweni Gaffneylania auricularis ? Warkalania carinaminor Gaffneylania auricularis ? Meiolania platyceps Niolamia provides important insight into
12194-645: The locality that the first Niolamia remains were found at and the general ambiguity around whether or not Ameghino's and Roth's skulls are distinct has led to a lot of confusion in subsequent years. Ameghino named the Guaranitic Formation in the Chubut Province as the place of origin of his fossils, claiming the material was collected near the Rio Sehuen and Rio Chubut . Woodward wrote that Roth's specimen meanwhile came from Cretaceous aged red sandstone, with
12328-485: 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
12462-421: 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
12596-490: 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
12730-469: 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
12864-420: The neuroanatomy of meiolaniids, which described the endocranial anatomy of Niolamia , Gaffneylania and Meiolania . Among the findings of the paper was that meiolaniids had an elongated vestibulum nasi. Although such a feature is associated with aquatic turtles today, correlating with a snorkel-like nose, it can also be interpreted as an adaptation for life in deserts based on extant lizards . In these lizards
12998-410: 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
13132-459: The opened underside seen in the more derived Meiolania . Phylogenetic analysis consistently recover Niolamia in the same position relative to other meiolaniid turtles, which is as the basalmost member and sister to all Australasian taxa. This placement is consistent with both its appearance in time and its place of origins, as this genus is older than all named species from Australia and the western pacific islands. The bridge between Niolamia and
13266-399: 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
13400-524: The physically much different Meiolania is somewhat bridged by Ninjemys , typically recovered as the basalmost of the Australasian forms, as it shares multiple traits including the laterally directed horns and large A scale area with Niolamia . The later description of Gaffneylania , also from the Neogene of Argentina, did not change this placement much. However, this is in part due to the fragmentary nature of
13534-469: The potential for additional uses, the enhanced sense of smell inferred by the large nasal cavity could have served several functions from foraging to intraspecific communication. Particular focus is placed on the later, with modern turtles displaying a wide variety of glands used to produce chemical secretions (musk glands, cloacal secretions and mental glands). While the presence of these glands cannot be observed in meiolaniid fossils, they may have been tied to
13668-441: The presence of trabecular bone with the pachycephalosaurids , headbutting is still considered an unlikely behavior. Part of the reasoning behind this is that in pachycephalosaurids the shock of impacts is in part observed by their enlarged dome-like head structures, which as such are not present in Niolamia . The team further notes that the trabecular bone is more prominent in the horns and frills, yet these elements are positioned in
13802-571: The primarily Gondwanan Meiolaniformes , which at one point would have been found in both southern South America and Antarctica. Given the fact that South Tasmanian Sea formed between the Cretaceous and late Eocene, meiolaniids must have arrived in Australia by this time, as is confirmed by the fossil record. Antarctica and South America would remain connected until the opening of the Drake Passage during
13936-445: The primary study on the matter being published in 2024. The publication analyzed a variety of hypothetical combat behaviors performed with the head, including headbutting, locking of the horns and frill and sideways stabbing and the stresses such actions put on the skeleton. Generally, impacts with the snout, forehead and struggling using the notch between the frill and horns cause the least amount of stress, as opposed to caudal torsion of
14070-702: 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
14204-535: The region furthest back on the skull is covered by the A scale, which forms an "occipital crest". This crest appears as a large, upward directed frill with a deep notch along its middle. The B scales, which cover the horn cores formed by the squamosal bones , appear as large triangular elements directed to the side of the animal. These horns, which are similar to those of the Australian Ninjemys , are thought to have been even larger in life. The C scales sit before
14338-410: 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
14472-483: The same species mentioned previously by Ameghino. However, rather than using the name Niolamia , Woodward created the combination Miolania argentina based on an accidental misspelling of Meiolania . Despite declaring Niolamia a junior synonym , Ameghino seemingly concurred with Woodward, using the combination himself in later publications. However, Sterli raises the possibility that rather than accepting synonymity, Ameghino never meant to call his material Niolamia in
14606-434: The same specimen and that Ameghino misattributed the discovery to his brother. This would explain the improbability of two well preserved skulls being discovered in such quick succession by different teams and also explain why no researcher ever figured the Ameghino skull or compared it to the Roth material. Subsequently, Sterli refers to the neotype as the holotype in this publication. The purposeful lack of information on
14740-399: The same time Moreno authored a short communication describing the material Roth reportedly uncovered on his second expedition. Although various postcranial remains were also described, the skull (specimen MLP 26–40) was the only element that was figured. Two years later Arthur Smith Woodward published a more detailed paper, in which he illustrated the material more extensively and assigned it to
14874-481: The scale placed atop the midline of the skull, extends between the G scales in Crossochelys , while no such split occurs in Niolamia . The fact that the X scales in derived meiolaniids, such as Ninjemys and Warkalania , forms an extension like that of Crossochelys suggests that this could be a paedomorphic trait in later members of the family. Among the features once considered to be diagnostic for Crossochelys
15008-400: The shape of the horns is also significantly downplayed compared to those of adult individuals. The large scales at the back of the skull for instance, Scales A, were initially interpreted as being separate in Crossochelys . Following the synonymty, this interpretation is either wrong or the scales would combine into a single element in adults, as exemplified by the neotype. The X scale, which is
15142-418: The shell appears to possess backwards directed spikes. Rather than holding its shape towards the back of the shell, the carapace of Niolamia forms a ditch at its rear-most point, creating an embayment bordered by the final supracaudal scale. The recovered pattern of sutures and scale sulci is similar to that of modern tortoises, but could not be compared to the shell of Meiolania , in which the number of scales
15276-430: The shell, reaching a maximum thickness of 1.5 cm (0.59 in). Of the ten recovered shell remains, only four have their position on the shell known. The largest fragment was likely located at the back edge of the carapace, correlating with the 8th costal plate (which cover the shell between its spine and edge) and the 10th & 11th peripheral plates (the bony plates forming the edge of the bony shell). In this region
15410-441: The skull is highly ankylosed , meaning the majority of sutures between the individual skull bones are fused and thus largely obscured. Only a few sutures are visible on the surface of the skull, primarily along the midline, however in ventral view (from the bottom) the connections between the bones are more clearly visible. Niolamia possesses a single opening for the nares , lacking any divisions in its internal structure. This sets
15544-415: The skullroof. Typically, this is a rather small scale surrounded on all sides by the much larger D and G scales. In Niolamia however, this scale is among the largest, appearing as a rectangular element that takes up the entire skullroof between the D scales and thus preventing them from touching each other. It further stands out due to being concave, rather than bulging out like the D and G scales. However it
15678-460: 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
15812-425: The stability of the head while walking. Given the similarities to modern turtles however, it is assumed that they were sensitive to low frequency sounds and not especially vocal animals, relying more heavily on smell. However as significant changes in the inner ear anatomy may often be subtle, a larger sample size would be needed to make more concrete observations for Niolamia and other meiolaniids. Generally, both
15946-430: 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
16080-441: The sutures between bones. The team does however note that it is theoretically possible that such a function may have been instead filled by the scutes that covered the skull in life. The team, led by Federico J. Degrange, concludes that though the animal's sense of smell was likely significant during courtship, it is more likely that the horns and frill served as a display structure rather than being used in intraspecific combat. Such
16214-417: The tail of Niolamia was covered in a series of protective bony rings that overlapped one another. These rings were roughly hexagonal in shape, with two pairs of spiky protrusions emerging. The top pair was more robust and directed upwards, while the smaller, lower pair was directed upwards and sideways. Unlike in Meiolania , and more like in Ninjemys , the tail rings of Niolamia were fully formed and lacked
16348-412: 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
16482-470: The top is covered by the unpaired scales Y and Z, extending from above the eyes to the elongated nasal bones. In addition to the skull, Niolamia is also known from a variety of postcranial remains. Elements of both shoulder girdles are described, as both the left and right preserve the elongated dorsal process of the scapula , which extends upwards in turtles. This process connects to the acromion at an obtuse angle (greater than 90°), which resembles what
16616-555: 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
16750-577: 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
16884-494: The word hypodigm in 1940, and published extensively on the taxonomy of fossil and extant mammals. Simpson was influentially, and incorrectly, opposed to Alfred Wegener 's theory of continental drift , but accepted the theory of plate tectonics (and continental drift) when the evidence became conclusive. He was Professor of Zoology at Columbia University , and Curator of the Department of Geology and Paleontology at
17018-457: Was an expert on extinct mammals and their intercontinental migrations. Simpson was extraordinarily knowledgeable about Mesozoic fossil mammals and fossil mammals of North and South America. He anticipated such concepts as punctuated equilibrium (in Tempo and Mode ) and dispelled the myth that the evolution of the horse was a linear process culminating in the modern Equus caballus . He coined
17152-744: Was awarded the Mary Clark Thompson Medal from the National Academy of Sciences . For his work, Tempo and mode in evolution , he was awarded the academy's Daniel Giraud Elliot Medal in 1944. He was elected to the American Academy of Arts and Sciences in 1948. He was awarded the Linnean Society of London 's prestigious Darwin-Wallace Medal in 1958. Simpson also received the Royal Society 's Darwin Medal 'In recognition of his distinguished contributions to general evolutionary theory, based on
17286-483: 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
17420-430: 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
17554-445: Was said to be another skull discovered by his brother . While Ameghino's name was retained for the animal, later publications were entirely based on Roth's material, as Ameghino neither diagnosed nor figured his fossil. The fact that Ameghino's material was never recovered after his initial communication has led some researchers to believe that the two specimens are one and the same. In 1898, British paleontologist Arthur Smith Woodward
17688-430: Was sent a photograph of a meiolaniid tail ring by fossil collector Santiago Roth , who worked under Francisco Pascasio Moreno . Woodward writes that he was able to study the fossil itself in early 1899 after the material was sent from Argentina to London , allowing him to compare it to the remains of Meiolania platyceps , a turtle named by Richard Owen from Australia . According to Woodward, Moreno tasked Roth with
17822-571: 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
17956-456: Was the presence of a "true temporal fenestra ", however this is likely simply the result of the sutures not yet being closed in the juvenile. Extinct Extinction 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
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