Insular dwarfism, a form of phyletic dwarfism, is the process and condition of large animals evolving or having a reduced body size when their population's range is limited to a small environment islands. This natural process is distinct from the intentional creation of dwarf breeds, called dwarfing; this process has occurred many times throughout evolutionary history, with examples including dinosaurs, like Europasaurus, modern animals such as elephants and their relatives. This process, other "island genetics" artifacts, can occur not only on islands, but in other situations where an ecosystem is isolated from external resources and breeding; this can include desert oases, isolated valleys and isolated mountains. Insular dwarfism is one aspect of the more general "island effect" or "Foster's rule", which posits that when mainland animals colonize islands, small species tend to evolve larger bodies, large species tend to evolve smaller bodies. There are several proposed explanations for the mechanism.
One is a selective process where only smaller animals trapped on the island survive, as food periodically declines to a borderline level. The smaller animals need fewer resources and smaller territories, so are more to get past the break-point where population decline allows food sources to replenish enough for the survivors to flourish. Smaller size is advantageous from a reproductive standpoint, as it entails shorter gestation periods and generation times. In the tropics, small size should make thermoregulation easier. Among herbivores, large size confers advantages in coping with both competitors and predators, so a reduction or absence of either would facilitate dwarfing. Among carnivores, the main factor is thought to be the size and availability of prey resources, competition is believed to be less important. In tiger snakes, insular dwarfism occurs on islands where available prey is restricted to smaller sizes than are taken by mainland snakes. Since prey size preference in snakes is proportional to body size, small snakes may be better adapted to take small prey.
The inverse process, wherein small animals breeding on isolated islands lacking the predators of large land masses may become much larger than normal, is called island gigantism. An excellent example is the ancestors of which were normal-sized pigeons. There are several species of giant rats, one still extant, that coexisted with both Homo floresiensis and the dwarf stegodons on Flores; the process of insular dwarfing can occur rapidly by evolutionary standards. This is in contrast to increases in maximum body size; when normalized to generation length, the maximum rate of body mass decrease during insular dwarfing was found to be over 30 times greater than the maximum rate of body mass increase for a ten-fold change in mammals. The disparity is thought to reflect the fact that pedomorphism offers a easy route to evolve smaller adult body size. For both herbivores and carnivores, island size, the degree of island isolation and the size of the ancestral continental species appear not to be of major direct importance to the degree of dwarfing.
However, when considering only the body masses of recent top herbivores and carnivores, including data from both continental and island land masses, the body masses of the largest species in a land mass were found to scale to the size of the land mass, with slopes of about 0.5 log per log. There were separate regression lines for endothermic top predators, ectothermic top predators, endothermic top herbivores and ectothermic top herbivores, such that food intake was 7 to 24-fold higher for top herbivores than for top predators, about the same for endotherms and ectotherms of the same trophic level. Recognition that insular dwarfism could apply to dinosaurs arose through the work of Ferenc Nopcsa, a Hungarian-born aristocrat, adventurer and paleontologist. Nopcsa studied Transylvanian dinosaurs intensively, noticing that they were smaller than their cousins elsewhere in the world. For example, he unearthed six-meter-long sauropods, a group of dinosaurs which elsewhere grew to 30 meters or more.
Nopcsa deduced that the area where the remains were found was an island, Hațeg Island during the Mesozoic era. Nopcsa's proposal of dinosaur dwarfism on Hațeg Island is today accepted after further research confirmed that the remains found are not from juveniles. In addition, the genus Balaur was described as a Velociraptor-sized dromaeosaurid, but has been since reclassified as a secondarily flightless stem bird, closer to modern birds than Jeholornis. Island gigantism Foster's rule Dwarfing Franz Nopcsa Island tameness Pleistocene extinctions Strange world of island species October 31, 2004 The Observer
The Paleocene or Palaeocene, the "old recent", is a geological epoch that lasted from about 66 to 56 million years ago. It is the first epoch of the Paleogene Period in the modern Cenozoic Era; as with many geologic periods, the strata that define the epoch's beginning and end are well identified, but the exact ages remain uncertain. The Paleocene Epoch is bracketed by two major events in Earth's history, it started with the mass extinction event at the end of the Cretaceous, known as the Cretaceous–Paleogene boundary. This was a time marked by the demise of non-avian dinosaurs, giant marine reptiles and much other fauna and flora; the die-off of the dinosaurs left unfilled ecological niches worldwide. The Paleocene ended with the Paleocene–Eocene Thermal Maximum, a geologically brief interval characterized by extreme changes in climate and carbon cycling; the name "Paleocene" comes from Ancient Greek and refers to the "old" "new" fauna that arose during the epoch. The K–Pg boundary that marks the separation between Cretaceous and Paleocene is visible in the geological record of much of the Earth by a discontinuity in the fossil fauna and high iridium levels.
There is fossil evidence of abrupt changes in flora and fauna. There is some evidence that a substantial but short-lived climatic change may have happened in the early decades of the Paleocene. There are several theories about the cause of the K–Pg extinction event, with most evidence supporting the impact of a 10 km diameter asteroid forming the buried Chicxulub crater on the coast of Yucatan, Mexico; the end of the Paleocene was marked by a time of major change, one of the most significant periods of global change during the Cenozoic. The Paleocene–Eocene Thermal Maximum upset oceanic and atmospheric circulation and led to the extinction of numerous deep-sea benthic foraminifera and a major turnover in mammals on land; the Paleocene is divided into three stages, the Danian, the Selandian and the Thanetian, as shown in the table above. Additionally, the Paleocene is divided into six Mammal Paleogene zones; the early Paleocene was cooler and drier than the preceding Cretaceous, though temperatures rose during the Paleocene–Eocene Thermal Maximum.
The climate became warm and humid worldwide towards the Eocene boundary, with subtropical vegetation growing in Greenland and Patagonia, crocodilians swimming off the coast of Greenland, early primates evolving in the tropical palm forests of northern Wyoming. The Earth's poles were temperate. In many ways, the Paleocene continued processes. During the Paleocene, the continents continued to drift toward their present positions. Supercontinent Laurasia had not yet separated into three continents - Europe and Greenland were still connected, North America and Asia were still intermittently joined by a land bridge, while Greenland and North America were beginning to separate; the Laramide orogeny of the late Cretaceous continued to uplift the Rocky Mountains in the American west, which ended in the succeeding epoch. South and North America remained separated by equatorial seas. Africa was heading north towards Europe closing the Tethys Ocean, India began its migration to Asia that would lead to a tectonic collision and the formation of the Himalayas.
The inland seas in North America and Europe had receded by the beginning of the Paleocene, making way for new land-based flora and fauna. Warm seas circulated including the poles; the earliest Paleocene featured a low diversity and abundance of marine life, but this trend reversed in the epoch. Tropical conditions gave rise including coral reefs. With the demise of marine reptiles at the end of the Cretaceous, sharks became the top predators. At the end of the Cretaceous, the ammonites and many species of foraminifera became extinct. Marine fauna came to resemble modern fauna, with only the marine mammals and the Carcharhinid sharks missing. Terrestrial Paleocene strata overlying the K–Pg boundary is in places marked by a "fern spike": a bed rich in fern fossils. Ferns are the first species to colonize areas damaged by forest fires. In general, the Paleocene is marked by the development of modern plant species. Cacti and palm trees appeared. Paleocene and plant fossils are attributed to modern genera or to related taxa.
The warm temperatures worldwide gave rise to thick tropical, sub-tropical and deciduous forest cover around the globe with ice-free polar regions covered with coniferous and deciduous trees. With no large browsing dinosaurs to thin them, Paleocene forests were denser than those of the Cretaceous. Flowering plants, first seen in the Cretaceous, continued to develop and proliferate, along with them coevolved the insects that fed on these plants and pollinated them. Mammals had first appeared in the Late Triassic, evolving from advanced cynodonts, developed alongside the dinosaurs, exploiting ecological niches untouched by the larger and more famous Mesozoic animals: in the insect-rich fo
Therizinosaurs were theropod dinosaurs belonging to the clade Therizinosauria. Therizinosaur fossils have been found in Early through Late Cretaceous deposits in Mongolia, the People's Republic of China, western North America and Australia. Various features of the forelimbs and pelvis unite these finds as both theropods and as maniraptorans, close relatives to birds; the name therizinosaur is derived from the Greek θερίζω therízein, meaning'to reap' or'to cut off', σαῦρος saûros meaning'lizard'. The older name segnosaur is derived from Latin segnis meaning'slow' or'sluggish', Greek σαυρος, meaning'lizard'. Therizinosaurs had a distinctive confusing set of characteristics, their long necks, wide torsos, hind feet with four toes used in walking resembled those of basal sauropodomorph dinosaurs. Their unique hip bones, which pointed backwards and were fused together reminded paleontologists of the "bird-hipped" ornithischians. Among the most striking characteristics of therizinosaurs are the enormous claws on their hands, which reached lengths of around one meter in Therizinosaurus.
The unusual range of motion in therizinosaur forelimbs, which allowed them to reach forward to a degree other theropods could not achieve supports the idea that they were herbivorous. Therizinosaurs may have used their long reach and curved claws to grasp and shear leafy branches, in a manner similar to large mammals that lived on, such as chalicotheres, ground sloths, great apes, giant pandas. Skin impressions from Beipiaosaurus indicate that therizinosaurs were covered with a coat of primitive, down-like feathers similar to those seen in the compsognathid Sinosauropteryx, as well as longer, quill-like feathers that may have been used in display. Therizinosaurs spanned a large range of sizes, from the small Beipiaosaurus, to the gigantic Therizinosaurus, which at an approximate 10 m long and an estimated weight of 5 tonnes, was among the largest-known theropods; because early finds were incomplete, the strange suite of anatomical features combining features typical of theropods and ornithischians led some scientists, such as Gregory S. Paul, to conclude that segnosaurs represented a late-surviving suborder of primitive dinosaurs, sometimes thought of as intermediates between prosauropods and ornithischians.
Because of their suspected relationship with prosauropods, early depictions of segnosaurs portrayed them as semi-quadrupedal, a mode of locomotion now known to have been impossible given the bird-like nature of their wrists. It led Paul to include segnosaurs within paleontologist Robert T. Bakker's Phytodinosauria in 1986, a superorder, to include ornithischians and sauropods, typified by their "blunt, spoon-crowned teeth suitable for cropping plants."It was not until the mid-1990s, after Alxasaurus was discovered and shown to possess more theropod features, Therizinosaurus was recognized as a member of the segnosaur group, that their true identity as herbivorous descendants of the carnivorous theropods became accepted. The relation between the more derived therizinosaurids and other theropods was elucidated by the discovery of primitive members of the group, such as Beipiaosaurus in 1999 and Falcarius in 2005; the scientists who described Falcarius noted that it seemed to represent an intermediate stage between carnivorous and herbivorous theropods, a sort of "missing link" between predatory maniraptorans and plant-eating therizinosaurs.
Although they are now classified as theropods, therizinosaurs had skulls similar to those of sauropods and the shape of their teeth and jaws make it that they were herbivores. Barsbold and Perle named the group Segnosauria as an infraorder of Theropoda in 1980. Dong Zhiming went further, placing the segnosaurs in Segnosaurischia; this name has been abandoned since the discovery that segnosaurs are a specialized group within the suborder Theropoda. Clark et al. in 2004 considered Segnosaurischia a synonym of Therizinosauroidea. The superfamily Therizinosauroidea had been established by Maleev in 1954, to include only the bizarre, giant-clawed theropod Therizinosaurus; when it was realized that Therizinosaurus was an advanced segnosaur, Therizinosauroidea was given a phylogenetic definition to include both groups, has replaced the use of the older name Segnosauria in phylogenetic studies because of the association of the name Segnosauria with the discredited idea that these animals were relatives of prosauropods.
The following taxonomy follows 2010 unless otherwise noted. Branch Therizinosauria Genus Eshanosaurus? Genus Falcarius Genus Martharaptor Genus Jianchangosaurus Superfamily Therizinosauroidea Genus Beipiaosaurus Genus Enigmosaurus Genus Erliansaurus Genus Neimongosaurus Genus Suzhousaurus Family Alxasauridae Family Therizinosauridae The clade Therizinosauria was first defined by Dale Russell in 1997 as Alxasaurus, Erlikosaurus, Segnosaurus and all taxa closer to them than to oviraptorosaurs and troodontids. Paul Sereno, in 2005, modified this definition to the most inclusive clade containing Therizinosaurus but not Ornithomimus, Shuvuuia, Tyrannosaurus, or Troodon. Therizinosauroidea named as a superfamily with no phylogenetic definition, was first defined by Zhang et al. in 2001, as the clade containing all theropods more related to Therizinosaurus than to birds (effectively replacing the
Ankylosauria is a group of herbivorous dinosaurs of the order Ornithischia. It includes the great majority of dinosaurs with armor in the form of bony osteoderms. Ankylosaurs were bulky quadrupeds, with powerful limbs, they are known to have first appeared in the early Jurassic Period, persisted until the end of the Cretaceous Period. They have been found on every continent; the first dinosaur discovered in Antarctica was the ankylosaurian Antarctopelta, fossils of which were recovered from Ross Island in 1986. Ankylosauria was first named by Henry Fairfield Osborn in 1923. In the Linnaean classification system, the group is considered either a suborder or an infraorder, it is contained within the group Thyreophora, which includes the stegosaurs, armored dinosaurs known for their combination of plates and spikes. They sported a small brain size in proportion to their body, second only to the Saurischian sauropods, they were rather slow moving because of the shortness of the limbs combined with being incapable of running.
Their top speed was less than 10 km/hour. All ankylosaurians had armor over much of their bodies scutes and nodules, with large spines in some cases; the scutes, or plates, are rectangular to oval objects organized in transverse rows with keels on the upper surface. Smaller nodules and plates filled in the open spaces between large plates. In all three groups, the first two rows of plates tend to form a sort of half-ring around the neck; the skull has armor plastered on to it, including a distinctive piece on the outside-rear of the lower jaw. Ankylosaurs were built low to the ground one foot off the ground surface, they had triangular teeth that were loosely packed, similar to stegosaurs. The large hyoid bones left in skeletons indicates that they had flexible tongues, they had a large, side secondary palate. This means that they could breathe unlike crocodiles, their expanded gut region suggests the use of fermentation to digest their food, using symbiotic bacteria and gut flora. Their diet consisted of ferns and angiosperms.
Mallon et al. examined herbivore coexistence on the island continent of Laramidia during the Late Cretaceous. It was concluded that ankylosaurs were restricted to feeding on vegetation at, or below, the height of 1 meter. Possible neonate-sized ankylosaur fossils have been documented in the scientific literature. Ankylosauria is split into two families: Nodosauridae and Ankylosauridae. A third family, the Polacanthidae, is sometimes used, but is more found to be a sub-group of one of the primary families; the first formal definition of Ankylosauria as a clade, a group containing all species of a certain evolutionary branch, was given in 1997 by Carpenter. He defined the group as all dinosaurs closer to Ankylosaurus than to Stegosaurus; this definition is followed by most paleontologists today. This "stem-based" definition means that the primitive armored dinosaur Scelidosaurus, closer to ankylosaurids than to stegosaurids, is technically a member of Ankylosauria. Upon the discovery of Bienosaurus, Dong Zhiming erected the family Scelidosauridae for both of these primitive ankylosaurs.
In 2001, Carpenter proposed a new group uniting Scelidosaurus, Ankylosauridae and Polacanthidae, with Minmi, to the exclusion of Stegosaurus. However, many taxonomists find; this group traditionally includes Nodosaurus and Sauropelta. The nodosauridae had longer snouts than their ankylosaurid cousins, they did not sport the archetypal'clubs' at the ends of their tails. Nodosaurids had muscular shoulders and a specialized knob of bone on each shoulder blade called the acromial process, it served as an attachment site for the muscles. These spines would be used for self-defense against predators, they had wide, flaring hips and thick limbs. They had smaller, narrow beaks than the ankylosaurids, which allowed them to be selective over what plant matter they grazed on. Most nodosaurid finds are from North America. Major differences distinguishing the ankylosaurids from the nodosaurids is that the ankylosaurids had bony clubs at the end of their tails, domed snouts in front of the eyes, large squamosal plates projecting from the top and bottom of each side of the skull, all of which nodosaurids lacked.
The traditional ankylosaurids are from in the Cretaceous. They had much wider bodies and have been discovered with bony eyelids; the large clubs at the end of their tails may have been used in sexual selection. This family included Ankylosaurus and Pinacosaurus; the clubs were made of several plates of bone that were permeated by soft tissue, allowing them to absorb thousands of pounds of force. Their beaks were larger and broader than the nodosaurids, indicating that these ankylosaurs were generalists in their diet; the family Polacanthidae was named by George Reber Wieland in 1911 to refer to a group of ankylosaurs that seemed to him to be intermediate between the ankylosaurids and nodosaurids. This grouping was ignored by most researchers until the late 1990s, when it was used as a subfamily by Kirkland for a natural group recovered by his 1998 analysi
Pachycephalosauria is a clade of ornithischian dinosaurs. Along with Ceratopsia, it makes up the clade Marginocephalia. Genera include Pachycephalosaurus and Prenocephale. With the exception of two species, most pachycephalosaurs lived during the Late Cretaceous Period, dating between about 85.8 and 65.5 million years ago. They are exclusive to all of them being found in North America and Asia, they were all herbivorous/omnivorous animals with thick skulls. Skulls can be domed, flat, or wedge-shaped depending on the species, are all ossified; the domes were surrounded by nodes and/or spikes. Partial skeletons have been found of several pachycephalosaur species, but to date no complete skeletons have been discovered. Isolated skull fragments are the only bones that are found. Candidates for the earliest known pachycephalosaur include Ferganocephale adenticulatum from Middle Jurassic Period strata of Kyrgyzstan and Stenopelix valdensis from Early Cretaceous strata of Germany, although R. M. Sullivan has doubted.
In 2017, a phylogenetic analysis conducted by Han and colleagues identified Stenopelix as a member of the Ceratopsia. Pachycephalosaurs were bipedal ornithischians characterized by their thickened skulls, they had a bulky torso with an expanded gut cavity and broad hips, short forelimbs, long legs, a short, thick neck, a heavy tail. Large orbits and a large optic nerve point to pachycephalosaurs having good vision, uncharacteristically large olfactory lobes indicate that they had a good sense of smell relative to other dinosaurs, they were small dinosaurs, with most falling in the range of 2–3 meters in length and the largest, Pachycephalosaurus wyomingensis, estimated to measure 4.5 meters long and weigh 450 kilograms. The characteristic skull of pachycephalosaurs is a result of the fusion and thickening of the frontals and parietals, accompanied by the closing of the supratemporal fenestra. In some species this takes the form of a raised dome. While the flat-headed pachycephalosaurs are traditionally regarded as distinct species or families, they may represent juveniles of dome-headed adults.
All display ornamented jugals and postorbitals in the form of blunt horns and nodes. Many species are only known from skull fragments, a complete pachycephalosaur skeleton is yet to be found; the adaptive significance of the skull dome has been debated. The popular hypothesis among the general public that the skull was used in head-butting, as sort of a dinosaurian battering ram, was first proposed by Colbert 1955; this view was popularized in the 1956 science fiction story "A Gun for Dinosaur" by L. Sprague de Camp. Many paleontologists have since argued for the head-butting hypothesis, including Galton 1970 and Sues 1978. In this hypothesis, pachycephalosaurs rammed each other head-on, as do modern-day mountain goats and musk oxen. Anatomical evidence for combative behavior includes vertebral articulations providing spinal rigidity, the shape of the back indicating strong neck musculature, it has been suggested that a pachycephalosaur could make its head and body horizontally straight, in order to transmit stress during ramming.
However, in no known dinosaur could the head and body be oriented in such a position. Instead, the cervical and anterior dorsal vertebrae of pachycephalosaurs show that the neck was carried in an "S"- or "U"-shaped curve; the rounded shape of the skull would lessen the contacted surface area during head-butting, resulting in glancing blows. Other possibilities include defense against predators, or both; the wide build of pachycephalosaurs and the squamosal horns of the Stygimoloch add credence to the flank-butting hypothesis. A histological study conducted by Goodwin & Horner 2004 argued against the battering ram hypothesis, they argued that the dome was "an ephemeral ontogenetic stage", the spongy bone structure could not sustain the blows of combat, the radial pattern was an effect of rapid growth. Biomechanical analyses by Snively & Cox 2008 and Snively & Theodor 2011 concluded, that the domes could withstand combat stresses. Lehman 2010 argued that the growth patterns discussed by Goodwin and Horner are not inconsistent with head-butting behavior.
Goodwin & Horner 2004 instead argued. There is evidence that the dome had some form of external covering, it is reasonable to consider the dome may have been brightly covered, or subject to change color seasonally. Due to the nature of the fossil record, however, it cannot be observed whether or not color played a role in dome function. Longrich, Sankey & Tanke 2010 argued that species recognition is an unlikely evolutionary cause for the dome, because dome forms are not notably different between species; because of this general similarity, several genera of Pachycephalosauridae have sometimes been incorrectly lumped together. This is unlike the case in ceratopsians and hadrosaurids, which had much more distinct cranial ornamentation. Longrich et al argued that instead the dome had a mechanical function, such as combat, one, important enough to justify the resource investment. Peterson et al studied cranial pathologies among the Pachycephalosauridae and found that 22% of all domes examined had lesions that are consistent with osteomyelitis, an infection of the bone resulting from penetrating trauma, or trauma to the tis
Antarctica is Earth's southernmost continent. It contains the geographic South Pole and is situated in the Antarctic region of the Southern Hemisphere entirely south of the Antarctic Circle, is surrounded by the Southern Ocean. At 14,200,000 square kilometres, it is the fifth-largest continent. For comparison, Antarctica is nearly twice the size of Australia. About 98% of Antarctica is covered by ice that averages 1.9 km in thickness, which extends to all but the northernmost reaches of the Antarctic Peninsula. Antarctica, on average, is the coldest and windiest continent, has the highest average elevation of all the continents. Most of Antarctica is a polar desert, with annual precipitation of only 200 mm along the coast and far less inland; the temperature in Antarctica has reached −89.2 °C, though the average for the third quarter is −63 °C. Anywhere from 1,000 to 5,000 people reside throughout the year at research stations scattered across the continent. Organisms native to Antarctica include many types of algae, fungi, plants and certain animals, such as mites, penguins and tardigrades.
Vegetation, where it occurs, is tundra. Antarctica is noted as the last region on Earth in recorded history to be discovered, unseen until 1820 when the Russian expedition of Fabian Gottlieb von Bellingshausen and Mikhail Lazarev on Vostok and Mirny sighted the Fimbul ice shelf; the continent, remained neglected for the rest of the 19th century because of its hostile environment, lack of accessible resources, isolation. In 1895, the first confirmed. Antarctica is a de facto condominium, governed by parties to the Antarctic Treaty System that have consulting status. Twelve countries signed the Antarctic Treaty in 1959, thirty-eight have signed it since then; the treaty prohibits military activities and mineral mining, prohibits nuclear explosions and nuclear waste disposal, supports scientific research, protects the continent's ecozone. Ongoing experiments are conducted by more than 4,000 scientists from many nations; the name Antarctica is the romanised version of the Greek compound word ἀνταρκτική, feminine of ἀνταρκτικός, meaning "opposite to the Arctic", "opposite to the north".
Aristotle wrote in his book Meteorology about an Antarctic region in c. 350 BC Marinus of Tyre used the name in his unpreserved world map from the 2nd century CE. The Roman authors Hyginus and Apuleius used for the South Pole the romanised Greek name polus antarcticus, from which derived the Old French pole antartike attested in 1270, from there the Middle English pol antartik in a 1391 technical treatise by Geoffrey Chaucer. Before acquiring its present geographical connotations, the term was used for other locations that could be defined as "opposite to the north". For example, the short-lived French colony established in Brazil in the 16th century was called "France Antarctique"; the first formal use of the name "Antarctica" as a continental name in the 1890s is attributed to the Scottish cartographer John George Bartholomew. The long-imagined south polar continent was called Terra Australis, sometimes shortened to'Australia' as seen in a woodcut illustration titled Sphere of the winds, contained in an astrological textbook published in Frankfurt in 1545.
Although the longer Latin phrase was better known, the shortened name Australia was used in Europe's scholarly circles. In the nineteenth century, the colonial authorities in Sydney removed the Dutch name from New Holland. Instead of inventing a new name to replace it, they took the name Australia from the south polar continent, leaving it nameless for some eighty years. During that period, geographers had to make do with clumsy phrases such as "the Antarctic Continent", they searched for a more poetic replacement, suggesting various names such as Antipodea. Antarctica was adopted in the 1890s. Antarctica has no indigenous population, there is no evidence that it was seen by humans until the 19th century. However, in February 1775, during his second voyage, Captain Cook called the existence of such a polar continent "probable" and in another copy of his journal he wrote:" believe it and it's more than probable that we have seen a part of it". However, belief in the existence of a Terra Australis—a vast continent in the far south of the globe to "balance" the northern lands of Europe and North Africa—had prevailed since the times of Ptolemy in the 1st century AD.
In the late 17th century, after explorers had found that South America and Australia were not part of the fabled "Antarctica", geographers believed that the continent was much larger than its actual size. Integral to the story of the origin of Antarctica's name is that it was not named Terra Australis—this name was given to Australia instead, because of the misconception that no significant landmass could exist further south. Explorer Matthew Flinders, in particular, has been credited with popularising the transfer of the name Terra Australis to Australia, he justified the titling of his book A Voyage to Terra Australis by writing in the introduction: There is no probability, that any other detached body of land, of nearly equal extent, will be found in a more southern latitude.
Hadrosaurids, or duck-billed dinosaurs, are members of the ornithischian family Hadrosauridae. This group is known as the duck-billed dinosaurs for the flat duck-bill appearance of the bones in their snouts; the family, which includes ornithopods such as Edmontosaurus and Parasaurolophus, was a common group of herbivores during the Late Cretaceous Period in what is now Asia, Antarctica, South America, North America. Hadrosaurids are descendants of the Upper Jurassic/Lower Cretaceous iguanodontian dinosaurs and had a similar body layout. Like other ornithischians, hadrosaurids had a predentary bone and a pubic bone, positioned backwards in the pelvis. Hadrosauridae is divided into two principal subfamilies: the lambeosaurines, which had hollow cranial crests or tubes. Saurolophines tended to be bulkier than lambeosaurines. Lambeosaurines included the aralosaurins, tsintaosaurins and parasaurolophins, while saurolophines included the brachylophosaurins, kritosaurins and edmontosaurins. Hadrosaurids were facultative bipeds, with the young of some species walking on two legs and the adults walking on four.
Their jaws were evolved for grinding plants, with multiple rows of teeth replacing each other as the teeth wore down. Hadrosaurids were the first dinosaur family to be identified in North America - the first traces being found in 1855-1856 with the discovery of fossil teeth. Joseph Leidy examined the teeth, erected the genera Trachodon and Thespesius. One species was named Trachodon mirabilis. Trachodon included all sorts of cerapod dinosaurs, including ceratopsids, is now considered an invalid genus. In 1858, the teeth were associated with Leidy's eponymous Hadrosaurus foulkii, named after the fossil hobbyist William Parker Foulke. More and more teeth were found, resulting in more genera. A well preserved complete hadrosaurid specimen, AMNH 5060, was recovered in 1908 by the fossil collector Charles Hazelius Sternberg and his three sons, in Converse County, Wyoming. Analyzed by Henry Osborn in 1912, it has come to be known as the "Trachodon mummy"; this specimen's skin was completely preserved in the form of impressions.
The family Hadrosauridae was first used by Edward Drinker Cope in 1869. Since its creation, a major division has been recognized in the group between the hollow-crested subfamily Lambeosaurinae and the subfamily Saurolophinae known as Hadrosaurinae. Both of these have been robustly support in all recent literature. Phylogenetic analysis has increased the resolution of hadrosaurid relationships leading to the widespread usage of tribes to describe the finer relationships within each group of hadrosaurids.. Lambeosaurines have been traditionally split into Parasaurolophini and Lambeosaurini; these terms entered the formal literature in Evans and Reisz's 2007 redescription of Lambeosaurus magnicristatus. Lambeosaurini is defined as all taxa more related Lambeosaurus lambei than to Parasaurolophus walkeri, Parasaurolophini as all those taxa closer to P. walkeri than to L. lambei. In recent years Tsintaosaurini and Aralosaurini have emerged; the use of the term Hadrosaurinae was questioned in a comprehensive study of hadrosaurid relationships by Albert Prieto-Márquez in 2010.
Prieto-Márquez noted that, though the name Hadrosaurinae had been used for the clade of crestless hadrosaurids by nearly all previous studies, its type species, Hadrosaurus foulkii, has always been excluded from the clade that bears its name, in violation of the rules for naming animals set out by the ICZN. Prieto-Márquez defined Hadrosaurinae as just the lineage containing H. foulkii, used the name Saurolophinae instead for the traditional grouping. Hadrosauridae was first defined as a clade, by Forster, in a 1997 abstract, as "Lambeosaurinae plus Hadrosaurinae and their most recent common ancestor". In 1998, Paul Sereno defined the clade Hadrosauridae as the most inclusive possible group containing Saurolophus and Parasaurolophus emending the definition to include Hadrosaurus, the type genus of the family, which ICZN rules state must be included, despite its status as a nomen dubium. According to Horner et al. Sereno's definition would place a few other well-known hadrosaurs outside the family, which led them to define the family to include Telmatosaurus by default.
Prieto-Marquez reviewed the phylogeny of Hadrosauridae in 2010, including many taxa within the family. Below is a cladogram from al.. 2016. This cladogram is a recent modification of the original 2010 analysis, including more characters and taxa; the resulting cladistic tree of their analysis was resolved using Maximum-Parsimony. 61 hadrosauroid species were included, characterized for 273 morphological features: 189 for cranial features and 84 for postcranial features. When characters had multiple states that formed an evolutionary scheme, they were ordered to account for the evolution of one state into the next; the final tree was run through TNT version 1.0. The most recognizable aspect of hadrosaur anatomy is the flattened and laterally stretched rostral bones, which gives the distinct duck-bill look, some members of the hadrosaurs had massive crests on their heads for display. In some genera, including Edmontosaurus, the whole fron