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139-580: The formation is known for its paleontological resources, including dinosaur remains that are found in the Late Cretaceous part of the formation, and it includes aquifers that are important sources of water for the area. The Denver Formation rests on the Arapahoe Formation , and its base is marked by the first appearance of tuffaceous sediments. It is overlain by the Dawson Arkose . In 2002

278-511: A nomen dubium that was indistinguishable from other Edmontosaurus . In 2020, Ryuji Takasaki and colleagues agreed that the Prince Creek remains should be classified as Edmontosaurus , though species designation is unclear because the specimens are juveniles. Another study found the Alaskan material to be referable to Edmontosaurus cf. regalis based on craniomandibular anatomy. Edmontosaurus

417-471: A jigsaw puzzle . Rocks normally form relatively horizontal layers, with each layer younger than the one underneath it. If a fossil is found between two layers whose ages are known, the fossil's age must lie between the two known ages. Because rock sequences are not continuous, but may be broken up by faults or periods of erosion , it is very difficult to match up rock beds that are not directly next to one another. However, fossils of species that survived for

556-480: A body of intrusive monzonite located several miles to the northwest, probably represents the volcanic vent from which the flows erupted. Generally referred to as basaltic , they are classified either as monzonite (the lowest flow) and latite (the upper two flows), or as shoshonite . They contain the minerals augite , plagioclase , and olivine altered to serpentine , with accessory sanidine and/or orthoclase , apatite , magnetite , and biotite . One of

695-461: A brief consensus until post-1910, when new material from Canada and Montana showed a greater diversity of hadrosaurids than previously suspected. Charles W. Gilmore , in 1915, reassessed hadrosaurids and recommended that Thespesius be reintroduced for hadrosaurids from the Lance Formation and rock units of equivalent age and that Trachodon , based on inadequate material, should be restricted to

834-544: A collision that formed the Moon about 40 million years later, may have cooled quickly enough to have oceans and an atmosphere about 4,440  million years ago . There is evidence on the Moon of a Late Heavy Bombardment by asteroids from 4,000 to 3,800 million years ago . If, as seems likely, such a bombardment struck Earth at the same time, the first atmosphere and oceans may have been stripped away. Paleontology traces

973-602: A common ancestor. Ideally the "family tree" has only two branches leading from each node ("junction"), but sometimes there is too little information to achieve this, and paleontologists have to make do with junctions that have several branches. The cladistic technique is sometimes fallible, as some features, such as wings or camera eyes , evolved more than once, convergently  – this must be taken into account in analyses. Evolutionary developmental biology , commonly abbreviated to "Evo Devo", also helps paleontologists to produce "family trees", and understand fossils. For example,

1112-451: A constant rate. These " molecular clocks ", however, are fallible, and provide only a very approximate timing: for example, they are not sufficiently precise and reliable for estimating when the groups that feature in the Cambrian explosion first evolved, and estimates produced by different techniques may vary by a factor of two. Earth formed about 4,570  million years ago and, after

1251-403: A data source that is not limited to animals with easily fossilised hard parts, and they reflect organisms' behaviours. Also many traces date from significantly earlier than the body fossils of animals that are thought to have been capable of making them. Whilst exact assignment of trace fossils to their makers is generally impossible, traces may for example provide the earliest physical evidence of

1390-685: A distinction between the " Iguanodon -like" Claosaurus annectens and the "duck-billed" Hadrosaurus (based on remains now known as adult Edmontosaurus annectens ), while Hatcher explicitly identified C. annectens as synonymous with the hadrosaurid represented by those same duck-billed skulls. Hatcher's revision, published in 1902, was sweeping, as he considered almost all hadrosaurid genera then known as synonyms of Trachodon . This included Cionodon , Diclonius , Hadrosaurus , Ornithotarsus , Pteropelyx , and Thespesius , as well as Claorhynchus and Polyonax , which are fragmentary genera now thought to be ceratopsians . Hatcher's work led to

1529-540: A few specimens. Edmontosaurus has had a very long and complicated history in paleontology, having spent decades with various species classified in other genera. Its taxonomic history intertwines at various points with the genera Agathaumas , Anatosaurus , Anatotitan , Claosaurus , Hadrosaurus , Thespesius , and Trachodon , with references predating the 1980s typically using Anatosaurus , Claosaurus , Thespesius , or Trachodon for edmontosaur fossils (excluding those assigned to E. regalis ) depending on

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1668-567: A fortunate accident during other research. For example, the 1980 discovery by Luis and Walter Alvarez of iridium , a mainly extraterrestrial metal, in the Cretaceous – Paleogene boundary layer made asteroid impact the most favored explanation for the Cretaceous–Paleogene extinction event – although debate continues about the contribution of volcanism. A complementary approach to developing scientific knowledge, experimental science ,

1807-460: A hadrosaurid from the older Judith River Formation and its equivalents. In regards to Claosaurus annectens , he recommended that it be considered the same as Thespesius occidentalis . His reinstatement of Thespesius for Lance-age hadrosaurids would have other consequences for the taxonomy of Edmontosaurus in the following decades. During this time frame (1902–1915), two additional important specimens of C. annectens were recovered. The first,

1946-438: A hadrosaurid, Edmontosaurus was a large terrestrial herbivore . Its teeth were continually replaced and packed into dental batteries that contained hundreds of teeth, only a relative handful of which were in use at any time. It used its broad beak to cut loose food, perhaps by cropping, or by closing the jaws in a clamshell-like manner over twigs and branches and then stripping off the more nutritious leaves and shoots. Because

2085-486: A large lower jaw that Marsh had named Trachodon longiceps in 1890, and a new species named Anatosaurus copei for two skeletons on display at the American Museum of Natural History that had long been known as Diclonius mirabilis (or variations thereof). Thus, the various species became Anatosaurus annectens , A. copei , A. edmontoni , A. longiceps , and A. saskatchewanensis . Anatosaurus would come to be called

2224-433: A metre long. One skull of E. annectens (formerly Anatotitan ) measures 3.87 feet (1.18 m) long. The skull was roughly triangular in profile, with no bony cranial crest. Viewed from above, the front and rear of the skull were expanded, with the broad front forming a duck-bill or spoon-bill shape. The beak was toothless, and both the upper and lower beaks were extended by keratinous material. Substantial remains of

2363-814: A minor group until the first jawed fish appeared in the Late Ordovician . The spread of animals and plants from water to land required organisms to solve several problems, including protection against drying out and supporting themselves against gravity . The earliest evidence of land plants and land invertebrates date back to about 476  million years ago and 490  million years ago respectively. Those invertebrates, as indicated by their trace and body fossils, were shown to be arthropods known as euthycarcinoids . The lineage that produced land vertebrates evolved later but very rapidly between 370  million years ago and 360  million years ago ; recent discoveries have overturned earlier ideas about

2502-441: A position the thigh bone would have pushed against the joint of the ilium and pubis, instead of pushing only against the solid ilium. The nine fused hip vertebrae provided support for the hip. The fore legs were shorter and less heavily built than the hind legs. The upper arm had a large deltopectoral crest for muscle attachment, while the ulna and radius were slim. The upper arm and forearm were similar in length. The wrist

2641-555: A rapid increase in knowledge about the history of life on Earth and to progress in the definition of the geologic time scale , largely based on fossil evidence. Although she was rarely recognised by the scientific community, Mary Anning was a significant contributor to the field of palaeontology during this period; she uncovered multiple novel Mesozoic reptile fossils and deducted that what were then known as bezoar stones are in fact fossilised faeces . In 1822 Henri Marie Ducrotay de Blainville , editor of Journal de Physique , coined

2780-535: A relatively short time can be used to link up isolated rocks: this technique is called biostratigraphy . For instance, the conodont Eoplacognathus pseudoplanus has a short range in the Middle Ordovician period. If rocks of unknown age are found to have traces of E. pseudoplanus , they must have a mid-Ordovician age. Such index fossils must be distinctive, be globally distributed and have a short time range to be useful. However, misleading results are produced if

2919-453: A second species or as a synonym of A. copei . Because the type species of Anatosaurus ( A. annectens ) was sunk into Edmontosaurus , the name Anatosaurus is abandoned as a junior synonym of Edmontosaurus . The conception of Edmontosaurus that emerged included three valid species: the type species E. regalis , E. annectens (including Anatosaurus edmontoni , amended to edmontonensis ), and E. saskatchewanensis . The debate about

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3058-405: A skull and skeleton lacking the beak, most of the tail, and part of the feet. It was discovered in 1916 by George F. Sternberg . Lambe found that his new dinosaur compared best to Diclonius mirabilis (specimens now assigned to Edmontosaurus annectens ) and drew attention to the size and robustness of Edmontosaurus . Initially, Lambe only described the skulls of the two skeletons, but returned to

3197-524: A soft tissue crest or wattle on the head. It is unknown whether such a crest was present on E. annectens , and whether it was an indicator of sexual dimorphism . A preserved rhamphotheca present in the E. annectens specimen LACM 23502, housed in the Los Angeles County Museum , indicates the beak of Edmontosaurus was more hook-shaped and extensive than many illustrations in scientific and public media have previously depicted. Whether or not

3336-604: A steady increase in brain size after about 3  million years ago . There is a long-running debate about whether modern humans are descendants of a single small population in Africa , which then migrated all over the world less than 200,000 years ago and replaced previous hominine species, or arose worldwide at the same time as a result of interbreeding . Life on earth has suffered occasional mass extinctions at least since 542  million years ago . Despite their disastrous effects, mass extinctions have sometimes accelerated

3475-432: A synonym of E. annectens as well. Anatosaurus edmontoni was mistakenly listed as a synonym of E. annectens in both reviews of Dinosauria, but this does not appear to be the case. E. annectens differed from E. regalis by having a longer, lower, and less robust skull and the lack of a comb-like crest. Although Brett-Surman regarded E. regalis and E. annectens as potentially representing males and females of

3614-808: A year to form. They were composed of six types of tissues, rivaling the complexity of mammal teeth. They grew in columns, with an observed maximum of six in each, and the number of columns varied based on the animal's size. Known column counts for the two species are: 51 to 53 columns per maxilla and 48 to 49 per dentary (teeth of the upper jaw being slightly narrower than those in the lower jaw) for E. regalis ; and 52 columns per maxilla and 44 per dentary for E. annectens (an E. saskatchewanensis specimen). The number of vertebrae differs between specimens. E. regalis had thirteen neck vertebrae, eighteen back vertebrae, nine hip vertebrae, and an unknown number of tail vertebrae. A specimen once identified as belonging to Anatosaurus edmontoni (now considered to be

3753-594: Is a skull and partial skeleton from the Wood Mountain plateau of southern Saskatchewan . He had collected this specimen in 1921 from rocks that were assigned to the Lance Formation, now the Frenchman Formation . NMC 8509 included an almost complete skull, numerous vertebrae, partial shoulder and hip girdles, and partial legs, representing the first substantial dinosaur specimen recovered from Saskatchewan. Sternberg opted to assign it to Thespesius because that

3892-469: Is a synonym of E. annectens . Specifically, the long, low skull of A. copei is the result of ontogenetic change and represents mature E. annectens individuals. Edmontosaurus is currently regarded as having two valid species: the type species E. regalis and E. annectens . E. regalis is known only from the Horseshoe Canyon Formation of Alberta, dating from the late Campanian age of

4031-681: Is also anatomically similar to Edmontosaurus ; M. K. Brett-Surman found the two to differ only in details related to the greater size of Shantungosaurus , based on what had been described of the latter genus. While the status of Edmontosaurus as a saurolophine has not been challenged, its exact placement within the clade is uncertain. Early phylogenies , such as that presented in R. S. Lull and Nelda Wright's influential 1942 monograph , had Edmontosaurus and various species of Anatosaurus (most of which would be later considered as additional species or specimens of Edmontosaurus ) as one lineage among several lineages of "flat-headed" hadrosaurs. One of

4170-667: Is also at least one report of a much larger potential E. annectens specimen that is almost 12 metres (39 ft) long. Two specimens still under study in the collection of the Museum of the Rockies - a 7.5 m (25 ft) tail labelled as MOR 1142 and another labelled as MOR 1609 - indicate that Edmontosaurus annectens could have grown to much larger sizes and reach nearly 15 metres (49 ft) in length, similar to Shantungosaurus which weighed 13 metric tons (14 short tons), but such large individuals were likely very rare. A 2022 study on

4309-511: Is classified as a genus of saurolophine (or hadrosaurine ) hadrosaurid, a member of the group of hadrosaurids that lacked large, hollow crests and instead had smaller, solid crests or fleshy combs. The first fossils named Edmontosaurus were discovered in southern Alberta (named after Edmonton , the capital city), in the Horseshoe Canyon Formation (formerly called the lower Edmonton Formation). The type species , E. regalis ,

Denver Formation - Misplaced Pages Continue

4448-543: Is composed of primarily of light-grey to brown, lenticular bedded , loosely cemented silty claystone , mudstone , siltstone , tuffaceous sandstone and, in some areas, andesitic conglomerate . Beds of low-rank coal and carbonaceous shale occur in the upper 500 feet (150 m) in some areas. Several early Paleocene lava flows are present in the upper part of the Denver Formation at North and South Table Mountain near Golden, Colorado . The Ralston Dike,

4587-584: Is composed only of eukaryotic cells, and the earliest evidence for it is the Francevillian Group Fossils from 2,100  million years ago , although specialisation of cells for different functions first appears between 1,430  million years ago (a possible fungus) and 1,200  million years ago (a probable red alga ). Sexual reproduction may be a prerequisite for specialisation of cells, as an asexual multicellular organism might be at risk of being taken over by rogue cells that retain

4726-477: Is hard to decide at what level to place a new higher-level grouping, e.g. genus or family or order ; this is important since the Linnaean rules for naming groups are tied to their levels, and hence if a group is moved to a different level it must be renamed. Paleontologists generally use approaches based on cladistics , a technique for working out the evolutionary "family tree" of a set of organisms. It works by

4865-436: Is limited to late Maastrichtian rocks and is represented by at least twenty skulls, some with postcranial remains. One author, Kraig Derstler, has described E. annectens as "perhaps the most perfectly-known dinosaur to date [1994]." Anatosaurus copei and E. saskatchewanensis are now thought to be growth stages of E. annectens , with A. copei as adults and E. saskatchewanensis as juveniles. Trachodon longiceps may be

5004-443: Is often said to work by conducting experiments to disprove hypotheses about the workings and causes of natural phenomena. This approach cannot prove a hypothesis, since some later experiment may disprove it, but the accumulation of failures to disprove is often compelling evidence in favor. However, when confronted with totally unexpected phenomena, such as the first evidence for invisible radiation , experimental scientists often use

5143-594: Is one that contained an extinct "crocodile-like" marine reptile, which eventually came to be known as the mosasaurid Mosasaurus of the Cretaceous period. The first half of the 19th century saw geological and paleontological activity become increasingly well organised with the growth of geologic societies and museums and an increasing number of professional geologists and fossil specialists. Interest increased for reasons that were not purely scientific, as geology and paleontology helped industrialists to find and exploit natural resources such as coal. This contributed to

5282-401: Is our only means of giving rocks greater than about 50 million years old an absolute age, and can be accurate to within 0.5% or better. Although radiometric dating requires very careful laboratory work, its basic principle is simple: the rates at which various radioactive elements decay are known, and so the ratio of the radioactive element to the element into which it decays shows how long ago

5421-451: Is the scientific study of life that existed prior to the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossils to classify organisms and study their interactions with each other and their environments (their paleoecology ). Paleontological observations have been documented as far back as the 5th century BC. The science became established in

5560-503: Is thought to have been propelled by coevolution with pollinating insects. Social insects appeared around the same time and, although they account for only small parts of the insect "family tree", now form over 50% of the total mass of all insects. Humans evolved from a lineage of upright-walking apes whose earliest fossils date from over 6  million years ago . Although early members of this lineage had chimp -sized brains, about 25% as big as modern humans', there are signs of

5699-513: The "mummified" specimen AMNH 5060 , was discovered in 1908 by Charles Hazelius Sternberg and his sons in Lance Formation rocks near Lusk , Wyoming. Sternberg was working for the British Museum of Natural History , but Henry Fairfield Osborn of the American Museum of Natural History was able to purchase the specimen for $ 2,000. The Sternbergs recovered a second similar specimen from

Denver Formation - Misplaced Pages Continue

5838-460: The Cretaceous period 73 million years ago, while those of E. annectens were found in the same geographic region from rocks dated to the end of the Maastrichtian age, 66 million years ago. Edmontosaurus was one of the last non- avian dinosaurs to ever exist, and lived alongside dinosaurs like Triceratops , Tyrannosaurus , Ankylosaurus , and Pachycephalosaurus shortly before

5977-474: The Cretaceous–Paleogene extinction event . Edmontosaurus included two of the largest hadrosaurid species, with E. annectens measuring up to 12 metres (39 ft) in length and weighing around 5.6 metric tons (6.2 short tons) in average asymptotic body mass, although some individuals would have been much larger. Several well-preserved specimens are known that include numerous bones, as well as extensive skin impressions and possible gut contents. Edmontosaurus

6116-482: The Hell Creek Formation of North Dakota . In a 2011 study by Nicolás Campione and David Evans, the authors conducted the first ever morphometric analysis to compare the various specimens assigned to Edmontosaurus . They concluded that only two species are valid: E. regalis , from the late Campanian, and E. annectens , from the late Maastrichtian. Their study provided further evidence that Anatotitan copei

6255-528: The International Commission on Zoological Nomenclature , which regulates the naming of organisms, his conclusions were known to other paleontologists and were adopted by several popular works of the time. Brett-Surman and Ralph Chapman designated a new genus for A. copei ( Anatotitan ) in 1990. Of the remaining species, A. saskatchewanensis and A. edmontoni were assigned to Edmontosaurus as well and A. longiceps went to Anatotitan as either

6394-567: The Middle Ages the Persian naturalist Ibn Sina , known as Avicenna in Europe, discussed fossils and proposed a theory of petrifying fluids on which Albert of Saxony elaborated in the 14th century. The Chinese naturalist Shen Kuo (1031–1095) proposed a theory of climate change based on the presence of petrified bamboo in regions that in his time were too dry for bamboo. In early modern Europe ,

6533-528: The Neogene - Quaternary . In deeper-level deposits in western Europe are early-aged mammals such as the palaeothere perissodactyl Palaeotherium and the anoplotheriid artiodactyl Anoplotherium , both of which were described earliest after the former two genera, which today are known to date to the Paleogene period. Cuvier figured out that even older than the two levels of deposits with extinct large mammals

6672-637: The Permian–Triassic extinction event . Amphibians Extinct Synapsids Mammals Extinct reptiles Lizards and snakes Extinct Archosaurs Crocodilians Extinct Dinosaurs Birds Naming groups of organisms in a way that is clear and widely agreed is important, as some disputes in paleontology have been based just on misunderstandings over names. Linnaean taxonomy is commonly used for classifying living organisms, but runs into difficulties when dealing with newly discovered organisms that are significantly different from known ones. For example: it

6811-513: The Permian–Triassic extinction event . A relatively recent discipline, molecular phylogenetics , compares the DNA and RNA of modern organisms to re-construct the "family trees" of their evolutionary ancestors. It has also been used to estimate the dates of important evolutionary developments, although this approach is controversial because of doubts about the reliability of the " molecular clock ". Techniques from engineering have been used to analyse how

6950-454: The embryological development of some modern brachiopods suggests that brachiopods may be descendants of the halkieriids , which became extinct in the Cambrian period. Paleontology seeks to map out how living things have changed through time. A substantial hurdle to this aim is the difficulty of working out how old fossils are. Beds that preserve fossils typically lack the radioactive elements needed for radiometric dating . This technique

7089-418: The paratype . Both were collected in 1891 by John Bell Hatcher from the late Maastrichtian-age Upper Cretaceous Lance Formation of Niobrara County (then part of Converse County ), Wyoming . This species has some historical footnotes attached, as it is among the first dinosaurs to receive a skeletal restoration and is the first hadrosaurid so restored. YPM 2182 and UNSM 2414 are, respectively,

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7228-413: The " Trachodon mummy " of the early 20th century, and the specimen nicknamed " Dakota ", the latter apparently including remnant organic compounds from the skin. Because of these finds, the scalation of Edmontosaurus annectens is known for most areas of the body. Skin impressions are less well known for E. regalis , but some well-preserved examples have been studied, including one which preserves

7367-521: The " jigsaw puzzles " of biostratigraphy (arrangement of rock layers from youngest to oldest). Classifying ancient organisms is also difficult, as many do not fit well into the Linnaean taxonomy classifying living organisms, and paleontologists more often use cladistics to draw up evolutionary "family trees". The final quarter of the 20th century saw the development of molecular phylogenetics , which investigates how closely organisms are related by measuring

7506-465: The "classic duck-billed dinosaur." This state of affairs persisted for several decades until Michael K. Brett-Surman reexamined the pertinent material for his graduate studies in the 1970s and 1980s. He concluded that the type species of Anatosaurus , A. annectens , was actually a species of Edmontosaurus and that A. copei was different enough to warrant its own genus. Although theses and dissertations are not regarded as official publications by

7645-463: The 18th century as a result of Georges Cuvier 's work on comparative anatomy , and developed rapidly in the 19th century. The term has been used since 1822 formed from Greek παλαιός ( 'palaios' , "old, ancient"), ὄν ( 'on' , ( gen. 'ontos' ), "being, creature"), and λόγος ( 'logos' , "speech, thought, study"). Paleontology lies on the border between biology and geology , but it differs from archaeology in that it excludes

7784-630: The Dawson Arkose are also included in the D1 Sequence. The Denver Formation consists of alluvial fan , fluvial , and paludal deposits that accumulated at the foot of the growing Rocky Mountain Front Ranges. It ranges in thickness from 600 feet (180 m) to 1,580 feet (480 m) in the central part of the Denver Basin. It is characterized by significant amounts of andesitic volcanic debris, and

7923-548: The Denver Formation was included as part of a larger unconformity-bounded unit named the D1 sequence, in order to facilitate basin-wide studies and avoid confusion arising from the lateral and vertical facies changes that occur within the Denver Basin. The base of the D1 is marked by the abrupt facies change at the top of the Laramie Formation, and its top is placed at the base of a regional paleosol series. The Arapahoe Formation and

8062-548: The Early Cambrian , along with several "weird wonders" that bear little obvious resemblance to any modern animals. There is a long-running debate about whether this Cambrian explosion was truly a very rapid period of evolutionary experimentation; alternative views are that modern-looking animals began evolving earlier but fossils of their precursors have not yet been found, or that the "weird wonders" are evolutionary "aunts" and "cousins" of modern groups. Vertebrates remained

8201-459: The Earth's organic and inorganic past". William Whewell (1794–1866) classified paleontology as one of the historical sciences, along with archaeology , geology, astronomy , cosmology , philology and history itself: paleontology aims to describe phenomena of the past and to reconstruct their causes. Hence it has three main elements: description of past phenomena; developing a general theory about

8340-497: The Horseshoe Canyon Formation. It was based on NMC 8399, another nearly complete skeleton lacking most of the tail. NMC 8399 was discovered on the Red Deer River in 1912 by a Sternberg party. Its arms, ossified tendons, and skin impressions were briefly described in 1913 and 1914 by Lambe, who at first thought it was an example of a species he had named Trachodon marginatus , but then changed his mind. The specimen became

8479-532: The Senckenberg Museum specimen have been described, but have proven difficult to interpret. The plants found in the carcass included needles of the conifer Cunninghamites elegans , twigs from conifer and broadleaf trees, and numerous small seeds or fruits. Upon their description in 1922, they were the subject of a debate in the German-language journal Paläontologische Zeitschrift . Kräusel, who described

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8618-470: The Senckenberg plant fossils remain equivocal. Kenneth Carpenter has suggested that they may actually represent the gut contents of a starving animal, instead of a typical diet. Other authors have noted that because the plant fossils were removed from their original context in the specimen and were heavily prepared, it is no longer possible to follow up on the original work, leaving open the possibility that

8757-412: The ability to reproduce. The earliest known animals are cnidarians from about 580  million years ago , but these are so modern-looking that they must be descendants of earlier animals. Early fossils of animals are rare because they had not developed mineralised , easily fossilized hard parts until about 548  million years ago . The earliest modern-looking bilaterian animals appear in

8896-515: The appearance of moderately complex animals (comparable to earthworms ). Geochemical observations may help to deduce the global level of biological activity at a certain period, or the affinity of certain fossils. For example, geochemical features of rocks may reveal when life first arose on Earth, and may provide evidence of the presence of eukaryotic cells, the type from which all multicellular organisms are built. Analyses of carbon isotope ratios may help to explain major transitions such as

9035-408: The aquatic-terrestrial dichotomy, until it was brought up by John Ostrom in the course of an article reassessing the old interpretation of hadrosaurids as water-bound. Instead of trying to adapt the discovery to the aquatic model, he used it as a line of evidence that hadrosaurids were terrestrial herbivores. While his interpretation of hadrosaurids as terrestrial animals has been generally accepted,

9174-625: The atmosphere increased their effectiveness as nurseries of evolution. While eukaryotes , cells with complex internal structures, may have been present earlier, their evolution speeded up when they acquired the ability to transform oxygen from a poison to a powerful source of metabolic energy. This innovation may have come from primitive eukaryotes capturing oxygen-powered bacteria as endosymbionts and transforming them into organelles called mitochondria . The earliest evidence of complex eukaryotes with organelles (such as mitochondria) dates from 1,850  million years ago . Multicellular life

9313-452: The author and the date. Although Edmontosaurus was only named in 1917, its oldest well-supported species ( E. annectens ) was named in 1892 as a species of Claosaurus . The first well-supported species of Edmontosaurus was named in 1892 as Claosaurus annectens by Othniel Charles Marsh . This species is based on USNM  2414, which is a partial skull-roof and skeleton, with a second skull and skeleton, YPM  2182, designated as

9452-442: The back and tail were lined by ossified tendons arranged in a latticework along the neural spines of the vertebrae. This condition has been described as making the back and at least part of the tail "ramrod" straight. The ossified tendons are interpreted as having strengthened the vertebral column against gravitational stress, incurred through being a large animal with a horizontal vertebral column otherwise supported mostly by

9591-415: The bodies of ancient organisms might have worked, for example the running speed and bite strength of Tyrannosaurus , or the flight mechanics of Microraptor . It is relatively commonplace to study the internal details of fossils using X-ray microtomography . Paleontology, biology, archaeology, and paleoneurobiology combine to study endocranial casts (endocasts) of species related to humans to clarify

9730-401: The causes of various types of change; and applying those theories to specific facts. When trying to explain the past, paleontologists and other historical scientists often construct a set of one or more hypotheses about the causes and then look for a " smoking gun ", a piece of evidence that strongly accords with one hypothesis over any others. Sometimes researchers discover a "smoking gun" by

9869-763: The characteristics and evolution of humans as a species. When dealing with evidence about humans, archaeologists and paleontologists may work together – for example paleontologists might identify animal or plant fossils around an archaeological site , to discover the people who lived there, and what they ate; or they might analyze the climate at the time of habitation. In addition, paleontology often borrows techniques from other sciences, including biology, osteology , ecology, chemistry , physics and mathematics. For example, geochemical signatures from rocks may help to discover when life first arose on Earth, and analyses of carbon isotope ratios may help to identify climate changes and even to explain major transitions such as

10008-520: The chronological order in which rocks were formed, is useful to both paleontologists and geologists. Biogeography studies the spatial distribution of organisms, and is also linked to geology, which explains how Earth's geography has changed over time. Although paleontology became established around 1800, earlier thinkers had noticed aspects of the fossil record. The ancient Greek philosopher Xenophanes (570–480 BCE) concluded from fossil sea shells that some areas of land were once under water. During

10147-508: The comparison between various specimens of different sizes from the Ruth Mason Dinosaur Quarry and other specimens from different localities. According to this analysis, E. regalis may have been heavier, but not enough samples exist to provide a valid estimate and examination on its osteohistology and growth, so the results for E. regalis aren't statistically significant. The skull of a fully grown Edmontosaurus could be over

10286-445: The date when lineages first appeared. For instance, if fossils of B or C date to X million years ago and the calculated "family tree" says A was an ancestor of B and C, then A must have evolved more than X million years ago. It is also possible to estimate how long ago two living clades diverged – i.e. approximately how long ago their last common ancestor must have lived – by assuming that DNA mutations accumulate at

10425-586: The development of mammalian traits such as endothermy and hair. After the Cretaceous–Paleogene extinction event 66  million years ago killed off all the dinosaurs except the birds, mammals increased rapidly in size and diversity, and some took to the air and the sea. Fossil evidence indicates that flowering plants appeared and rapidly diversified in the Early Cretaceous between 130  million years ago and 90  million years ago . Their rapid rise to dominance of terrestrial ecosystems

10564-551: The development of the body plans of most animal phyla . The discovery of fossils of the Ediacaran biota and developments in paleobiology extended knowledge about the history of life back far before the Cambrian. Increasing awareness of Gregor Mendel 's pioneering work in genetics led first to the development of population genetics and then in the mid-20th century to the modern evolutionary synthesis , which explains evolution as

10703-477: The different levels of deposits represented different time periods in the early 19th century. The surface-level deposits in the Americas contained later mammals like the megatheriid ground sloth Megatherium and the mammutid proboscidean Mammut (later known informally as a "mastodon"), which were some of the earliest-named fossil mammal genera with official taxonomic authorities. They today are known to date to

10842-409: The end of the 20th century have been particularly important as they have provided new information about the earliest evolution of animals, early fish, dinosaurs and the evolution of birds. The last few decades of the 20th century saw a renewed interest in mass extinctions and their role in the evolution of life on Earth. There was also a renewed interest in the Cambrian explosion that apparently saw

10981-499: The evolution of life on earth. When dominance of an ecological niche passes from one group of organisms to another, this is rarely because the new dominant group outcompetes the old, but usually because an extinction event allows a new group, which may possess an advantageous trait, to outlive the old and move into its niche. Edmontosaurus Edmontosaurus ( / ɛ d ˌ m ɒ n t ə ˈ s ɔːr ə s / ed- MON -tə- SOR -əs ) (meaning "lizard from Edmonton "), with

11120-410: The evolution of the human brain. Paleontology even contributes to astrobiology , the investigation of possible life on other planets , by developing models of how life may have arisen and by providing techniques for detecting evidence of life. As knowledge has increased, paleontology has developed specialised subdivisions. Vertebrate paleontology concentrates on fossils from the earliest fish to

11259-466: The evolutionary history of life back to over 3,000  million years ago , possibly as far as 3,800  million years ago . The oldest clear evidence of life on Earth dates to 3,000  million years ago , although there have been reports, often disputed, of fossil bacteria from 3,400  million years ago and of geochemical evidence for the presence of life 3,800  million years ago . Some scientists have proposed that life on Earth

11398-555: The exceptional events that cause quick burial make it difficult to study the normal environments of the animals. The sparseness of the fossil record means that organisms are expected to exist long before and after they are found in the fossil record – this is known as the Signor–Lipps effect . Trace fossils consist mainly of tracks and burrows, but also include coprolites (fossil feces ) and marks left by feeding. Trace fossils are particularly significant because they represent

11537-444: The eye sockets. Another rarely seen bone, the stapes (the reptilian ear bone), has also been seen in a specimen of Edmontosaurus . It has been suggested that Edmontosaurus may have had binocular vision based on the 3D scan of a nearly complete skull of E. regalis (CMN 2289). Teeth were present only in the maxillae (upper cheeks) and dentaries (main bone of the lower jaw). The teeth were continually replaced, taking about half

11676-531: The first analyses using cladistic methods found it to be linked with Anatosaurus (= Anatotitan ) and Shantungosaurus in an informal "edmontosaur" clade, which was paired with the spike-crested "saurolophs" and more distantly related to the "brachylophosaurs" and arch-snouted "gryposaurs". A 2007 study by Terry Gates and Scott Sampson found broadly similar results, in that Edmontosaurus remained close to Saurolophus and Prosaurolophus and distant from Gryposaurus , Brachylophosaurus , and Maiasaura . However,

11815-509: The first and second essentially complete mounted dinosaur skeletons in the United States. YPM 2182 was put on display in 1901 and USNM 2414 was put on display in 1904. Because of the incomplete understanding of hadrosaurids at the time, following Marsh's death in 1897, Claosaurus annectens was variously classified as a species of Claosaurus , Thespesius or Trachodon . Opinions varied greatly, as textbooks and encyclopedias drew

11954-536: The first dinosaur skeleton to be mounted for exhibition in a Canadian museum. Gilmore found that his new species compared closely to what he called Thespesius annectens , but left the two apart because of details of the arms and hands. He also noted that his species had more vertebrae than Marsh's in the back and neck, but proposed that Marsh was mistaken in assuming that the annectens specimens were complete in those regions. In 1926, Charles Mortram Sternberg named Thespesius saskatchewanensis for NMC 8509, which

12093-472: The flows hosts a wide variety of zeolite minerals , including analcime , thomsonite , mesolite , chabazite , and others. The Denver Formation spans the Cretaceous-Paleogene boundary . The lava flows in the upper part of the formation are about 62 to 64 million years old according to radiometric dating , which places them in the early Paleocene Epoch . The Cretaceous-Paleogene boundary occurs in

12232-504: The focus of paleontology shifted to understanding evolutionary paths, including human evolution , and evolutionary theory. The last half of the 19th century saw a tremendous expansion in paleontological activity, especially in North America. The trend continued in the 20th century with additional regions of the Earth being opened to systematic fossil collection. Fossils found in China near

12371-449: The following: At the end of the 18th century Georges Cuvier 's work established comparative anatomy as a scientific discipline and, by proving that some fossil animals resembled no living ones, demonstrated that animals could become extinct , leading to the emergence of paleontology. The expanding knowledge of the fossil record also played an increasing role in the development of geology, particularly stratigraphy . Cuvier proved that

12510-580: The fossil record: different environments are more favorable to the preservation of different types of organism or parts of organisms. Further, only the parts of organisms that were already mineralised are usually preserved, such as the shells of molluscs. Since most animal species are soft-bodied, they decay before they can become fossilised. As a result, although there are 30-plus phyla of living animals, two-thirds have never been found as fossils. Occasionally, unusual environments may preserve soft tissues. These lagerstätten allow paleontologists to examine

12649-423: The genus in 1920 to describe the skeleton of NMC 2289. The postcrania of the type specimen remains undescribed, still in its plaster jackets to this day. Two more species that would come to be included with Edmontosaurus were named from Canadian remains in the 1920s, but both would initially be assigned to Thespesius . Gilmore named the first, Thespesius edmontoni , in 1924. T. edmontoni also came from

12788-430: The group include Brachylophosaurus , Gryposaurus , Lophorhothon , Maiasaura , Naashoibitosaurus , Prosaurolophus , and Saurolophus . It was either closely related to or includes the species Anatosaurus annectens (alternately Edmontosaurus annectens ), a large hadrosaurid from various latest Cretaceous formations of western North America. The giant Chinese hadrosaurine Shantungosaurus giganteus

12927-446: The hind legs and hips. The shoulder blades were long flat blade-like bones, held roughly parallel to the vertebral column. The hips were composed of three elements each: an elongate ilium above the articulation with the leg, an ischium below and behind with a long thin rod, and a pubis in front that flared into a plate-like structure. The structure of the hip hindered the animal from standing with its back erect, because in such

13066-675: The history and driving forces behind their evolution. Land plants were so successful that their detritus caused an ecological crisis in the Late Devonian , until the evolution of fungi that could digest dead wood. During the Permian period, synapsids , including the ancestors of mammals , may have dominated land environments, but this ended with the Permian–Triassic extinction event 251  million years ago , which came very close to wiping out all complex life. The extinctions were apparently fairly sudden, at least among vertebrates. During

13205-521: The history of Earth's climate and the mechanisms that have changed it  – which have sometimes included evolutionary developments, for example the rapid expansion of land plants in the Devonian period removed more carbon dioxide from the atmosphere, reducing the greenhouse effect and thus helping to cause an ice age in the Carboniferous period. Biostratigraphy , the use of fossils to work out

13344-542: The immediate ancestors of modern mammals . Invertebrate paleontology deals with fossils such as molluscs , arthropods , annelid worms and echinoderms . Paleobotany studies fossil plants , algae , and fungi. Palynology , the study of pollen and spores produced by land plants and protists , straddles paleontology and botany , as it deals with both living and fossil organisms. Micropaleontology deals with microscopic fossil organisms of all kinds. Instead of focusing on individual organisms, paleoecology examines

13483-434: The index fossils turn out to have longer fossil ranges than first thought. Stratigraphy and biostratigraphy can in general provide only relative dating ( A was before B ), which is often sufficient for studying evolution. However, this is difficult for some time periods, because of the problems involved in matching up rocks of the same age across different continents . Family-tree relationships may also help to narrow down

13622-550: The inner face of the upper beak. This interpretation of the beak has been rejected, as the furrows and ridges are more like those of herbivorous turtle beaks than the flexible structures seen in filter-feeding birds. Because scratches dominate the microwear texture of the teeth, Williams et al. suggested Edmontosaurus was a grazer instead of a browser , which would be predicted to have fewer scratches due to eating less abrasive materials. Candidates for ingested abrasives include silica -rich plants like horsetails and soil that

13761-538: The interactions between different ancient organisms, such as their food chains , and the two-way interactions with their environments.   For example, the development of oxygenic photosynthesis by bacteria caused the oxygenation of the atmosphere and hugely increased the productivity and diversity of ecosystems . Together, these led to the evolution of complex eukaryotic cells, from which all multicellular organisms are built. Paleoclimatology , although sometimes treated as part of paleoecology, focuses more on

13900-463: The internal anatomy of animals that in other sediments are represented only by shells, spines, claws, etc. – if they are preserved at all. However, even lagerstätten present an incomplete picture of life at the time. The majority of organisms living at the time are probably not represented because lagerstätten are restricted to a narrow range of environments, e.g. where soft-bodied organisms can be preserved very quickly by events such as mudslides; and

14039-456: The investigation of evolutionary "family trees" by techniques derived from biochemistry , began to make an impact, particularly when it was proposed that the human lineage had diverged from apes much more recently than was generally thought at the time. Although this early study compared proteins from apes and humans, most molecular phylogenetics research is now based on comparisons of RNA and DNA . Fossils of organisms' bodies are usually

14178-549: The keratinous upper beak are known from the "mummy" kept at the Senckenberg Museum . In this specimen, the preserved nonbony part of the beak extended for at least 8 centimetres (3.1 in) beyond the bone, projecting down vertically. The nasal openings of Edmontosaurus were elongate and housed in deep depressions surrounded by distinct bony rims above, behind, and below. In at least one case (the Senckenberg specimen), rarely preserved sclerotic rings were preserved in

14317-574: The late Cretaceous period. At least a dozen individuals are known, including seven skulls with associated postcrania and five to seven other skulls. The species formerly known as Thespesius edmontoni or Anatosaurus edmontoni represents immature individuals of E. regalis . E. annectens is known from the Frenchman Formation of Saskatchewan, the Hell Creek Formation of Montana, and the Lance Formation of South Dakota and Wyoming. It

14456-618: The legs, but were long enough to be used for standing or for quadrupedal movement. Depending on the species, previous estimates suggested that a fully grown adult could have been 9–12 metres (30–39 ft) long and some of the larger specimens reached the range of 12–13 metres (39–43 ft) with a body mass on the order of 4 metric tons (4.4 short tons). E. annectens is often seen as smaller. Two mounted skeletons, USNM  2414 and YPM  2182, measure 8.00 metres (26.25 ft) long and 8.92 metres (29.3 ft) long, respectively. However, these are probably subadult individuals There

14595-409: The logic that, if groups B and C have more similarities to each other than either has to group A, then B and C are more closely related to each other than either is to A. Characters that are compared may be anatomical , such as the presence of a notochord , or molecular , by comparing sequences of DNA or proteins . The result of a successful analysis is a hierarchy of clades – groups that share

14734-1313: The lower part of the formation, and an exposure of the boundary layer has been identified and documented on South Table Mountain near the city of Golden . Plant fossils and remains of vertebrates , including turtles and mammals , are found throughout the Denver Formation. Dinosaur remains are restricted to the lower, Late Cretaceous, part. Cionodon C. arctatus "Fragmentary maxilla, vertebrae, fragmentary postcranial elements." Later found to be indeterminate hadrosaurid remains. Edmontosaurus Indeterminate Pachycephalosaurus Indeterminate Polyonax P. mortuarius "Horn fragments, vertebrae." ( type specimen ) A dubious ceratopsian Triceratops T. galeus "Nasal horn core." A dubious ceratopsian Indeterminate Aublysodon A. mirandus Later found to be indeterminate tyrannosauroid remains. Ornithomimus O. velox Tyrannosaurus Indeterminate 39°44′N 104°59′W  /  39.74°N 104.98°W  / 39.74; -104.98  ( Denver Formation ) Paleontology Paleontology ( / ˌ p eɪ l i ɒ n ˈ t ɒ l ə dʒ i , ˌ p æ l i -, - ən -/ PAY -lee-on- TOL -ə-jee, PAL -ee-, -⁠ən- ), also spelled palaeontology or palæontology ,

14873-517: The material, interpreted it as the gut contents of the animal, while Abel could not rule out that the plants had been washed into the carcass after death. At the time, hadrosaurids were thought to have been aquatic animals, and Kräusel made a point of stating that the specimen did not rule out hadrosaurids eating water plants. The discovery of possible gut contents made little impact in English-speaking circles, except for another brief mention of

15012-409: The most informative type of evidence. The most common types are wood, bones, and shells. Fossilisation is a rare event, and most fossils are destroyed by erosion or metamorphism before they can be observed. Hence the fossil record is very incomplete, increasingly so further back in time. Despite this, it is often adequate to illustrate the broader patterns of life's history. There are also biases in

15151-624: The most recent review of Hadrosauridae, by Jack Horner and colleagues (2004), came to a noticeably different result: Edmontosaurus was nested between Gryposaurus and the "brachylophosaurs", and distant from Saurolophus . Edmontosaurus is the namesake genus of the saurolophine tribe Edmontosaurini , which also includes taxa like Shantungosaurus , Kerberosaurus and Laiyangosaurus . Hadrosaurus Brachylophosaurini Kritosaurini Saurolophini Kamuysaurus Kerberosaurus Laiyangosaurus Shantungosaurus Edmontosaurus annectens Edmontosaurus regalis As

15290-500: The osteohistology and growth of E. annectens suggested that previous estimates might have underestimated or overestimated the size of this dinosaur and proposed that a fully grown adult E. annectens would have measured up to 11–12 metres (36–39 ft) in length and approximately 5.6 metric tons (6.2 short tons) in average asymptotic body mass, while the largest individuals measured more than 6 metric tons (6.6 short tons) and even up to 6.6–7 metric tons (7.3–7.7 short tons) when based on

15429-414: The outcome of events such as mutations and horizontal gene transfer , which provide genetic variation , with genetic drift and natural selection driving changes in this variation over time. Within the next few years the role and operation of DNA in genetic inheritance were discovered, leading to what is now known as the "Central Dogma" of molecular biology . In the 1960s molecular phylogenetics ,

15568-449: The prevailing interpretation of hadrosaurids like Edmontosaurus was that they were aquatic and fed on aquatic plants. An example of this is William Morris's 1970 interpretation of an edmontosaur skull with nonbony beak remnants. He proposed that the animal had a diet much like that of some modern ducks, filtering plants and aquatic invertebrates like mollusks and crustaceans from the water and discharging water via V-shaped furrows along

15707-452: The principal types of evidence about ancient life, and geochemical evidence has helped to decipher the evolution of life before there were organisms large enough to leave body fossils. Estimating the dates of these remains is essential but difficult: sometimes adjacent rock layers allow radiometric dating , which provides absolute dates that are accurate to within 0.5%, but more often paleontologists have to rely on relative dating by solving

15846-400: The proper taxonomy of the A. copei specimens continues to the present day. Returning to Hatcher's argument of 1902, Jack Horner, David B. Weishampel , and Catherine Forster regarded Anatotitan copei as representing specimens of Edmontosaurus annectens with crushed skulls. In 2007, another "mummy" was announced. Nicknamed " Dakota ", it was discovered in 1999 by Tyler Lyson and came from

15985-432: The radioactive element was incorporated into the rock. Radioactive elements are common only in rocks with a volcanic origin, and so the only fossil-bearing rocks that can be dated radiometrically are a few volcanic ash layers. Consequently, paleontologists must usually rely on stratigraphy to date fossils. Stratigraphy is the science of deciphering the "layer-cake" that is the sedimentary record, and has been compared to

16124-701: The same approach as historical scientists: construct a set of hypotheses about the causes and then look for a "smoking gun". Paleontology lies between biology and geology since it focuses on the record of past life, but its main source of evidence is fossils in rocks. For historical reasons, paleontology is part of the geology department at many universities: in the 19th and early 20th centuries, geology departments found fossil evidence important for dating rocks, while biology departments showed little interest. Paleontology also has some overlap with archaeology , which primarily works with objects made by humans and with human remains, while paleontologists are interested in

16263-580: The same area in 1910, which was not as well preserved. However, it was also found with skin impressions. They sold the specimen, SM 4036, to the Senckenberg Museum in Germany. As a side note, Trachodon selwyni , described by Lawrence Lambe in 1902 for a lower jaw from what is now known as the Dinosaur Park Formation of Alberta , was erroneously described by Glut (1997) as having been assigned to Edmontosaurus regalis by Lull and Wright. It

16402-411: The same as E. regalis ) is reported as having an additional back vertebra and 85 tail vertebrae, with an undisclosed amount of restoration. Other hadrosaurids are only reported as having 50 to 70 tail vertebrae, so this appears to have been an overestimate. The anterior back was curved toward the ground, with the neck flexed upward and the rest of the back and tail held horizontally. Most of

16541-504: The same species, all E. regalis specimens come from older formations than E. annectens specimens. Edmontosaurine specimens from the Prince Creek Formation of Alaska formerly assigned to Edmontosaurus sp. were given their own genus and species name, Ugrunaaluk kuukpikensis , in 2015. However, the identification of Ugrunaaluk as a separate genus was questioned by a 2017 study from Hai Xing and colleagues, who regarded it as

16680-408: The second species often colloquially and historically known as Anatosaurus or Anatotitan (meaning "duck lizard" and "giant duck"), is a genus of hadrosaurid (duck-billed) dinosaur . It contains two known species : Edmontosaurus regalis and Edmontosaurus annectens . Fossils of E. regalis have been found in rocks of western North America that date from the late Campanian age of

16819-478: The similarity of the DNA in their genomes . Molecular phylogenetics has also been used to estimate the dates when species diverged, but there is controversy about the reliability of the molecular clock on which such estimates depend. The simplest definition of "paleontology" is "the study of ancient life". The field seeks information about several aspects of past organisms: "their identity and origin, their environment and evolution, and what they can tell us about

16958-465: The slow recovery from this catastrophe a previously obscure group, archosaurs , became the most abundant and diverse terrestrial vertebrates. One archosaur group, the dinosaurs, were the dominant land vertebrates for the rest of the Mesozoic , and birds evolved from one group of dinosaurs. During this time mammals' ancestors survived only as small, mainly nocturnal insectivores , which may have accelerated

17097-556: The specimen in question preserved the true rhamphotheca or just a cast of the inner structure attached to the bone is not known at present. Edmontosaurus was a hadrosaurid (a duck-billed dinosaur), a member of a family of dinosaurs which to date are known only from the Late Cretaceous . It is classified within the Saurolophinae (alternately Hadrosaurinae), a clade of hadrosaurids which lacked hollow crests. Other members of

17236-631: The study of anatomically modern humans . It now uses techniques drawn from a wide range of sciences, including biochemistry , mathematics , and engineering. Use of all these techniques has enabled paleontologists to discover much of the evolutionary history of life , almost back to when Earth became capable of supporting life, nearly 4 billion years ago. As knowledge has increased, paleontology has developed specialised sub-divisions, some of which focus on different types of fossil organisms while others study ecology and environmental history, such as ancient climates . Body fossils and trace fossils are

17375-617: The systematic study of fossils emerged as an integral part of the changes in natural philosophy that occurred during the Age of Reason . In the Italian Renaissance, Leonardo da Vinci made various significant contributions to the field as well as depicted numerous fossils. Leonardo's contributions are central to the history of paleontology because he established a line of continuity between the two main branches of paleontology – ichnology and body fossil paleontology. He identified

17514-417: The tooth rows are deeply indented from the outside of the jaws, and because of other anatomical details, it is inferred that Edmontosaurus and most other ornithischians had cheek-like structures, muscular or non-muscular. The function of the cheeks was to retain food in the mouth. The animal's feeding range would have been from ground level to around 4 metres (13 ft) above. Before the 1960s and 1970s,

17653-406: The word "palaeontology" to refer to the study of ancient living organisms through fossils. As knowledge of life's history continued to improve, it became increasingly obvious that there had been some kind of successive order to the development of life. This encouraged early evolutionary theories on the transmutation of species . After Charles Darwin published Origin of Species in 1859, much of

17792-454: Was "seeded" from elsewhere , but most research concentrates on various explanations of how life could have arisen independently on Earth. For about 2,000 million years microbial mats , multi-layered colonies of different bacteria, were the dominant life on Earth. The evolution of oxygenic photosynthesis enabled them to play the major role in the oxygenation of the atmosphere from about 2,400  million years ago . This change in

17931-438: Was accidentally ingested due to feeding at ground level. The tooth structure indicates combined slicing and grinding capabilities. Reports of gastroliths , or stomach stones, in the hadrosaurid Claosaurus is actually based on a probable double misidentification. First, the specimen is actually of Edmontosaurus annectens . Barnum Brown , who discovered the specimen in 1900, referred to it as Claosaurus because E. annectens

18070-481: Was also reported from the Javelina Formation of Big Bend National Park , western Texas based on TMM 41442-1, but was later referred to Kritosaurus cf. navajovius by Wagner (2001), before being assigned to Kritosaurus sp. by Lehman et al. (2016). Edmontosaurus has been described in detail from numerous specimens. Traditionally, E. regalis has been regarded as the largest species, though this

18209-463: Was challenged by the hypothesis that the larger hadrosaurid Anatotitan copei is a synonym of Edmontosaurus annectens , as put forward by Jack Horner and colleagues in 2004, and supported in studies by Campione and Evans in 2011. Edmontosaurus was among the largest hadrosaurids to ever exist. Like other hadrosaurids, it was a bulky animal with a long, laterally flattened tail and an expanded, duck-like beak. The arms were not as heavily built as

18348-421: Was found. The Edmonton Formation lends Edmontosaurus its name. The type species , E. regalis (meaning "regal", or, more loosely, "king-sized"), is based on NMC  2288, which consists of a skull, articulated vertebrae up to the sixth tail vertebra, ribs, partial hips, an upper arm bone, and most of a leg. It was discovered in 1912 by Levi Sternberg. The second specimen, paratype NMC 2289, consists of

18487-560: Was much shorter. The thigh bone was robust and straight, with a prominent flange about halfway down the posterior side. This ridge was for the attachment of powerful muscles attached to the hips and tail that pulled the thighs (and thus the hind legs) backward and helped maintain the use of the tail as a balancing organ. Each foot had three toes, with no big toe or little toe. The toes had hoof-like tips. Multiple specimens of Edmontosaurus annectens have been found with preserved skin impressions. Several have been well-publicized, such as

18626-565: Was named by Lawrence Lambe in 1917, although several other species that are now classified in Edmontosaurus were named earlier. The best known of these is E. annectens , named by Othniel Charles Marsh in 1892. This species was originally as a species of Claosaurus , known for many years as a species of Trachodon , and later known as Anatosaurus annectens . Anatosaurus , Anatotitan , and probably Ugrunaaluk are now generally regarded as synonyms of Edmontosaurus . Edmontosaurus

18765-460: Was not, instead being designated "of very doubtful validity." More recent reviews of hadrosaurids have concurred. Edmontosaurus itself was coined in 1917 by Lawrence Lambe for two partial skeletons found in the Horseshoe Canyon Formation (formerly the lower Edmonton Formation) along the Red Deer River of southern Alberta. These rocks are older than the rocks in which Claosaurus annectens

18904-414: Was simple, with only two small bones. Each hand had four fingers, with no thumb (first finger). The index (second), third, and fourth fingers were approximately the same length and were united in life within a fleshy covering. Although the second and third finger had hoof-like unguals , these bones were also within the skin and not apparent from the outside. The little finger diverged from the other three and

19043-693: Was the only hadrosaurid genus known from the Lance Formation at the time. At the time, T. saskatchewanensis was unusual because of its small size, estimated at 7 to 7.3 metres (23 to 24 ft) in length. In 1942, Lull and Wright attempted to resolve the complicated taxonomy of crestless hadrosaurids by naming a new genus, Anatosaurus , to take in several species that did not fit well under their previous genera. Anatosaurus , meaning "duck lizard", because of its wide, duck-like beak ( Latin anas = duck + Greek sauros = lizard), had as its type species Marsh's old Claosaurus annectens . Also assigned to this genus were Thespesius edmontoni , T. saskatchewanensis ,

19182-512: Was thought to be a species of Claosaurus at the time. Additionally, it is more likely that the supposed gastroliths represent gravel washed in during burial. Both of the "mummy" specimens collected by the Sternbergs were reported to have had possible gut contents. Charles H. Sternberg reported the presence of carbonized gut contents in the American Museum of Natural History specimen, but this material has not been described. The plant remains in

19321-617: Was widely distributed across western North America, ranging from Colorado to the northern slopes of Alaska . The distribution of Edmontosaurus fossils suggests that it preferred coasts and coastal plains . It was a herbivore that could move on both two legs and four. Because it is known from several bone beds , Edmontosaurus is thought to have lived in groups and may have been migratory as well. The wealth of fossils has allowed researchers to study its paleobiology in detail, including its brain, how it may have fed, and its injuries and pathologies , such as evidence for tyrannosaur attacks on

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