Hadrosaurids, also commonly referred to as duck-billed
dinosaur
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...
s or hadrosaurs, were large terrestrial
herbivores. The diet of hadrosaurid dinosaurs remains a subject of debate among paleontologists, especially regarding whether hadrosaurids were
grazers who fed on vegetation close to the ground, or
browsers
Browse, browser or browsing may refer to:
Programs
* Web browser, a program used to access the World Wide Web
*Code browser, a program for navigating source code
* File browser or file manager, a program used to manage files and related objects
* ...
who ate higher-growing leaves and twigs. Preserved stomach content findings have indicated they may have been browsers, whereas other studies into jaw movements indicate they may have been grazers.
The mouth of a hadrosaur had hundreds of tiny teeth packed into
dental batteries. These teeth were continually replaced with new teeth.
Hadrosaur beaks were used to cut food, either by stripping off leaves
or by cropping.
It is believed hadrosaurs had cheeks in order to keep food in the mouth.
Researchers have long believed their unusual mouth mechanics may have played a role in their evolutionary success.
However, because they lack the complex flexible lower jaw joint of today's
mammals, it has been difficult for scientists to determine exactly how the hadrosaurs broke down their food and ate.
Without this understanding, it had been impossible to form a complete understanding of the
Late Cretaceous
The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', ...
ecosystems and how they were affected during the
Cretaceous–Paleogene extinction event
The Cretaceous–Paleogene (K–Pg) extinction event (also known as the Cretaceous–Tertiary extinction) was a sudden mass extinction of three-quarters of the plant and animal species on Earth, approximately 66 million years ago. With the ...
66 million years ago.
It has also remained unclear exactly what hadrosaurids ate. In particular, it has never been definitively proven whether hadrosaurs were
grazers who ate vegetation close to the ground, like modern-day
sheep
Sheep or domestic sheep (''Ovis aries'') are domesticated, ruminant mammals typically kept as livestock. Although the term ''sheep'' can apply to other species in the genus '' Ovis'', in everyday usage it almost always refers to domesticated ...
or
cows
Cattle (''Bos taurus'') are large, domesticated, cloven-hooved, herbivores. They are a prominent modern member of the subfamily Bovinae and the most widespread species of the genus ''Bos''. Adult females are referred to as cows and adult mal ...
, or whether the dinosaurs were
browsers
Browse, browser or browsing may refer to:
Programs
* Web browser, a program used to access the World Wide Web
*Code browser, a program for navigating source code
* File browser or file manager, a program used to manage files and related objects
* ...
who ate higher-growing leaves and twigs, like today's
deer
Deer or true deer are hoofed ruminant mammals forming the family Cervidae. The two main groups of deer are the Cervinae, including the muntjac, the elk (wapiti), the red deer, and the fallow deer; and the Capreolinae, including the re ...
or
giraffes.
A 2008–2009 study by
University of Leicester
, mottoeng = So that they may have life
, established =
, type = public research university
, endowment = £20.0 million
, budget = £326 million
, chancellor = David Willetts
, vice_chancellor = Nishan Canagarajah
, head_lab ...
researchers analyzed hundreds of microscopic scratches on the teeth of a fossilized ''
Edmontosaurus'' jaw and determined hadrosaurs had a unique way of eating unlike any creature living today. In contrast to a flexible lower jaw joint prevalent in today's mammals, a hadrosaur had a unique hinge between the upper jaws and the rest of its skull. The team found the dinosaur's upper jaws pushed outwards and sideways while chewing, as the lower jaw slid against the upper teeth.
Coprolite
A coprolite (also known as a coprolith) is fossilized feces. Coprolites are classified as trace fossils as opposed to body fossils, as they give evidence for the animal's behaviour (in this case, diet) rather than morphology. The name is de ...
s (fossilized droppings) of some Late
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...
hadrosaurs show that the animals sometimes deliberately ate rotting wood. Wood itself is not nutritious, but decomposing wood would have contained fungi, decomposed wood material and
detritus-eating
invertebrate
Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...
s, all of which would have been nutritious.
Early history of research
The first hadrosaur finds did not include much skull material. Hadrosaur teeth have been known since the 1850s (
Joseph Leidy
Joseph Mellick Leidy (September 9, 1823 – April 30, 1891) was an American paleontologist, parasitologist and anatomist.
Leidy was professor of anatomy at the University of Pennsylvania, later was a professor of natural history at Swarthmore ...
's ''
Trachodon
''Trachodon'' (meaning "rough tooth") is a dubious genus of hadrosaurid dinosaur based on teeth from the Campanian-age Upper Cretaceous Judith River Formation of Montana, U.S.Leidy, J. (1856). "Notice of remains of extinct reptiles and fishes ...
''),
and a few fragments of teeth and jaws were among the bones named ''
Hadrosaurus
''Hadrosaurus'' (; ) is a genus of hadrosaurid ornithopod dinosaurs that lived in North America during the Late Cretaceous Period in what is now the Woodbury Formation about 80 million to 78 million years ago. The holotype specimen was found in f ...
'' by Leidy in 1858.
(The skeletal mount made for ''Hadrosaurus'' by
Benjamin Waterhouse Hawkins
Benjamin Waterhouse Hawkins (8 February 1807 – 27 January 1894) was an English sculptor and natural history artist renowned for his work on the life-size models of dinosaurs in the Crystal Palace Park in south London. The models, accurately ...
included a speculative
iguana
''Iguana'' (, ) is a genus of herbivorous lizards that are native to tropical areas of Mexico, Central America, South America, and the Caribbean. The genus was first described in 1768 by Austrian naturalist Josephus Nicolaus Laurenti in his ...
-like skull)
Leidy had enough skeletal material to make other inferences about the
paleobiology
Paleobiology (or palaeobiology) is an interdisciplinary field that combines the methods and findings found in both the earth sciences and the life sciences. Paleobiology is not to be confused with geobiology, which focuses more on the interactio ...
of hadrosaurs, though. Of particular importance was the unequal lengths of the forelimbs and hindlimbs. He interpreted his new animal as a
kangaroo
Kangaroos are four marsupials from the family Macropodidae (macropods, meaning "large foot"). In common use the term is used to describe the largest species from this family, the red kangaroo, as well as the antilopine kangaroo, eastern ...
-like animal that browsed along rivers, using its forelimbs to manipulate branches.
[ His vague inference of amphibious habits would later be expanded upon by Edward Drinker Cope, who contributed the mistaken conclusion that hadrosaur teeth and jaws were weak and suitable only for eating soft water plants.][
]
Cope described the next piece of the puzzle in 1874: a more complete jaw fragment in 1874 he named '' Cionodon arctatus'', which revealed for the first time the complex hadrosaur tooth battery.[ However, the first essentially complete hadrosaur skull was not described until 1883. It was part of a skeleton (the first essentially complete hadrosaur skeleton as well) collected in 1882 by Dr. J. L. Wortman and R. S. Hill for Cope. Described as a specimen of '' Diclonius mirabilis'', it is now known as ''Edmontosaurus''.] Cope immediately drew attention to the anterior part of the skull, which was drawn out, long, and wide. He compared it to that of a goose
A goose ( : geese) is a bird of any of several waterfowl species in the family Anatidae. This group comprises the genera ''Anser'' (the grey geese and white geese) and '' Branta'' (the black geese). Some other birds, mostly related to the ...
in side view, and to a short-billed spoonbill in top view. Additionally, he noted the presence of what he interpreted as the remnants of a dermal structure surrounding the beak. Significantly, Cope regarded his ''Diclonius'' as an amphibious animal consuming soft water vegetation. His reasoning was that the teeth of the lower jaw were weakly connected to the bone and liable to break off if used to consume terrestrial food, and he described the beak as weak as well. Unfortunately for Cope, aside from misidentifying several of the bones of the skull, by chance the lower jaws he was studying were missing the walls supporting the teeth from the inside; the teeth were actually well-supported. While Cope anticipated publishing a full report with illustrations, he never did so, and instead the first accurate illustrated description of a hadrosaur skull and skeleton would be produced by his great rival, Othniel Charles Marsh
Othniel Charles Marsh (October 29, 1831 – March 18, 1899) was an American professor of Paleontology in Yale College and President of the National Academy of Sciences. He was one of the preeminent scientists in the field of paleontology. Among ...
. While Marsh corrected several anatomical errors, he retained Cope's postulated diet of soft plants.[ The description of hadrosaurs as amphibious eaters of aquatic plants became so ingrained that when the first possible case of hadrosaur gut contents was described in 1922 and found to be made up of terrestrial plants, the author made a point of noting that the specimen only established that hadrosaurs could eat land plants as well as water plants.]
Lull and Wright (1942)
The early study of hadrosaurid dietary adaptations and feeding behavior was summarized in a 1942 monograph by Richard Swann Lull
Richard Swann Lull (November 6, 1867 – April 22, 1957) was an American paleontologist and Sterling Professor at Yale University who is largely remembered now for championing a non-Darwinian view of evolution, whereby mutation(s) could unl ...
and Nelda Wright Nelda is a given name. Notable people with the name include:
* Nelda Garrone ( 1880–?), Italian mezzo-soprano
*Nelda Martinez (born 1961), American real estate agent and politician
*Nelda Speaks (born 1943), American politician
See also
*Zelda ...
. Unlike previous authors, they moved away from soft water plants as the major part of the diet, but retained the interpretation of an amphibious lifestyle. They drew attention to the extensive development of the hadrosaurid dental batteries, and compared their dental equipment to that of horses, noting the advantage the dinosaurs had in continual replacement of teeth. However, they found the purpose of the dental batteries uncertain: hadrosaur jaws were unlike those of any modern reptiles, and there did not appear to be an evolutionary pressure on hadrosaurids like grasses were for horses. Lull and Wright eliminated the soft plants as the primary choice of diet, and eliminated grasses on the grounds that the beak was unlike that of grazing birds like geese, and that the quantity of available grasses appeared insufficient to feed hadrosaurids. Instead, they proposed equisetaleans (horsetails) as the major food source, as these plants existed in the same times and places as hadrosaurids, are known to be rich in starch, and contain abrasive silica
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is ...
which would necessitate teeth that could be replaced. Softer land and water plants were proposed as secondary foods. Lull and Wright found that their proposed feeding ecology was comparable to that of a modern moose
The moose (in North America) or elk (in Eurasia) (''Alces alces'') is a member of the New World deer subfamily and is the only species in the genus ''Alces''. It is the largest and heaviest extant species in the deer family. Most adult ma ...
, which browses on trees and feeds on water plants in wetlands. They further interpreted the complex anatomy of hadrosaurid snouts and nasal passages as adaptations to feeding underwater, like moose.[Lull, Richard Swann; and Wright, Nelda E. (1942). ''Hadrosaurian Dinosaurs of North America''. p. 30–36.]
Lull and Wright added a new element to hadrosaurid feeding by proposing the presence of muscles analogous to mammalian cheek muscles, which would hold in food chopped by the teeth. These muscles would be attached on bony ridges present on the upper and lower jaws. The authors interpreted the action of the jaws as limited to simple up–and–down motions, finding forward–backward motion unlikely based on skull articulation. The vertical motion would cut food into short lengths, and the pieces would be retained by the cheeks. To manipulated the food in the cheeks, the authors inferred the presence of a well-developed tongue.[Lull, Richard Swann; and Wright, Nelda E. (1942). ''Hadrosaurian Dinosaurs of North America''. p. 100–101.]
Ostrom (1964) and reception
The general preexisting consensus on hadrosaurid paleobiology was challenged in 1964 by John Ostrom
John Harold Ostrom (February 18, 1928 – July 16, 2005) was an American paleontologist who revolutionized modern understanding of dinosaurs in the 1960s.
As first proposed by Thomas Henry Huxley in the 1860s, Ostrom showed that dinosaurs were ...
, who found little evidence to support either a diet of aquatic plants or an amphibious lifestyle. Unlike previous depictions, he interpreted hadrosaurids as terrestrial foragers that browsed on land plants, not aquatic plants. Like Lull and Wright, he drew attention to the robust dental batteries, and found that hard, resistant foods were the most likely diet (such as woody, silica–rich, or fibrous materials). Unlike Lull and Wright, he interpreted hadrosaur jaws as using a complex rodent–like forward–backward grinding motion, and did not comment on the possibility of cheeks. Drawing on an older proposal made during study of a hadrosaur specimen with a preserved beak, he noted the possibility that the animals stripped leaves and shoots from branches by closing the beak over branches and pulling back. A terrestrial diet was also supported by the 1922 gut content study, which found conifer needles and twigs, seeds, and fruits inside the specimen. There was also more circumstantial evidence for terrestrial feeding. Ostrom found that hadrosaurid skeletal anatomy indicated that the animals were well–adapted to move on land, and were well–supported by ossified
Ossification (also called osteogenesis or bone mineralization) in bone remodeling is the process of laying down new bone material by cells named osteoblasts. It is synonymous with bone tissue formation. There are two processes resulting in t ...
tendon
A tendon or sinew is a tough, high-tensile-strength band of dense fibrous connective tissue that connects muscle to bone. It is able to transmit the mechanical forces of muscle contraction to the skeletal system without sacrificing its ability ...
s along the vertebral spines, which would have hindered swimming. He also reported that aquatic plant pollen was rare in the rock units hadrosaurids are known from, which indicates that aquatic plants were uncommon.[
]
1984 hadrosaurid chewing hypothesis
In 1984, David B. Weishampel proposed a new hypothesis on how hadrosaurids fed. His study of the sutures between bones in fossil skulls concluded that ornithopod
Ornithopoda () is a clade of ornithischian dinosaurs, called ornithopods (), that started out as small, bipedal running grazers and grew in size and numbers until they became one of the most successful groups of herbivores in the Cretaceous wo ...
s, a group of bird-hipped dinosaurs that includes hadrosaurids, had flexible upper jaws and that when the lower jaw clamped shut, pressure would spread outward from both sides of the upper jaw. The upper teeth would grind against the lower teeth like rasps, trapping the plants and grinding them up. The theory remained largely unproven until the study by Purnell, Williams and Barrett, which ''Science
Science is a systematic endeavor that Scientific method, builds and organizes knowledge in the form of Testability, testable explanations and predictions about the universe.
Science may be as old as the human species, and some of the earli ...
'' magazine called, "The strongest independent evidence yet for this unique jaw motion". However, in 2008, a group of American and Canadian researchers, led by vertebrate paleobiologist Natalia Rybczynski, replicated Weishampel's proposed chewing motion using a computerized three-dimensional
Three-dimensional space (also: 3D space, 3-space or, rarely, tri-dimensional space) is a geometric setting in which three values (called ''parameters'') are required to determine the position of an element (i.e., point). This is the informa ...
animation model. Rybczynski ''et al.'' believe Weishampel's model may not be viable, and plan to test other hypotheses.
2008 preserved stomach content findings
In 2008, a team led by University of Colorado at Boulder
The University of Colorado Boulder (CU Boulder, CU, or Colorado) is a public research university in Boulder, Colorado. Founded in 1876, five months before Colorado became a state, it is the flagship university of the University of Colorado sy ...
graduate student Justin S. Tweet found a homogeneous accumulation of millimeter-scale leaf fragments in the gut region of a well-preserved partially grown ''Brachylophosaurus
''Brachylophosaurus'' ( or ; meaning "short-crested lizard", Greek ''brachys'' = short + ''lophos'' = crest + ''sauros'' = lizard, referring to its small crest) was a mid-sized member of the hadrosaurid family of dinosaurs. It is known from sev ...
''. As a result of that finding, Tweet concluded in September 2008 that the animal was likely a browser, not a grazer.
2008–2009 hadrosaur chewing study by Williams ''et al.''
A study into exactly how a hadrosaur broke down and ate its food was conducted by Vince Williams, a graduate student at the University of Leicester; Paul Barrett, a paleontologist
Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...
with London
London is the capital and List of urban areas in the United Kingdom, largest city of England and the United Kingdom, with a population of just under 9 million. It stands on the River Thames in south-east England at the head of a estuary dow ...
's Natural History Museum
A natural history museum or museum of natural history is a scientific institution with natural history collections that include current and historical records of animals, plants, fungi, ecosystems, geology, paleontology, climatology, and more. ...
; and Mark Purnell, a British paleontologist from the geology department of the University of Leicester
, mottoeng = So that they may have life
, established =
, type = public research university
, endowment = £20.0 million
, budget = £326 million
, chancellor = David Willetts
, vice_chancellor = Nishan Canagarajah
, head_lab ...
. The three men employed a new approach to analyze the feeding mechanisms of dinosaurs, and thus help understand their place in the prehistoric ecosystems. Chewing on solid food always leaves tiny scratches on the teeth's surfaces. The trio believed that by looking at the size and orientation of those markings on hadrosaurid teeth, they would be able to learn about the movements of their jaws. Purnell said although he believed this form of study could help determine how and what the hadrosaur ate, he said no previous studies had ever employed this type of analysis.
Williams, Barrett, and Purnell conducted their study using the jaws of an '' Edmontosaurus'', a hadrosaurid that lived between 68 and 66 million years ago in what is now the United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...
and Canada
Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
. The specific ''Edmontosaurus'' jaw used in this study was collected from Late Cretaceous rocks found in the United States. The individual teeth on the jaw contained multiple hundreds of microscopic scratches, which had been preserved intact during fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
ization. The researchers carefully cleaned the jaws, molded them and coated them with gold to make a detailed replica of the tooth surface. Then they used a scanning electron microscope to give high-power magnification of the scratches for study, and conducted a three-dimensional statistical analysis of the direction of the scratches.
The study found that the hadrosaur chewed using a method completely different from any creature living today, and utilized a type of jaw that is now extinct. The study found the ''Edmontosaurus'' jaw had four different sets of parallel scratches running in different directions. Purnell concluded each set of scratches related to a specific jaw movement. This revealed the movement of hadrosaurs was complex and employed movement in several different directions, including up-and-down, front-to-back and sideways movements. The trio concluded that in contrast to the flexible lower jaw joint prevalent in modern mammals, the hadrosaur had a hinge between its upper jaws and the rest of its skull. According to the study, the hadrosaur would push its upper jaws outwards and sideways, while the lower teeth slid against the upper teeth. As the tooth surfaces slid sideways across each other, the food would be ground and shredded before consumption. Purnell said the style of eating, "was not a scissor-like movement; it seems that these dinosaurs invented their own way of chewing." Although the upper-jaw teeth hinged outward when the hadrosaur ate, Purnell said it was likely the dinosaur could still chew with its mouth closed. While the outward flexure of the upper jaws might have been visible, Purnell said the chewing was likely concealed by the hadrosaur's cheeks and probably looked "quite subtle".
The study also made conclusions about what hadrosaurids ate, although Purnell cautioned the conclusions about the hadrosaur's diet were "a little less secure than the very good evidence we have for the motions of the teeth relative to each other." The scratches found on each individual tooth were so equal that measuring an area of just one square millimeter was enough to sample the whole jaw. The team concluded the evenness of the scratches suggested the hadrosaur used the same series of jaw motions over and over again. As a result, the study determined that the hadrosaur diet was probably made of leaves and lacked the bulkier items such as twigs or stems, which might have required a different chewing method and created different wear patterns. The lack of pit marks on the teeth also upheld these conclusions, and suggested the hadrosaurs likely grazed on low-lying vegetation that lacked pits, rather than browsing on higher-growing vegetation with twigs. The scratches also indicated the hadrosaur's food contained either small particles of grit, which was normal for vegetation cropped close to the ground, or that it contained microscopic granules of silica
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is ...
, which is common in grass
Poaceae () or Gramineae () is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species cultivated in lawns a ...
. Grasses had evolved by the Late Cretaceous period, but were not particularly common, so the study concluded it probably did not play a major component in the hadrosaur's diet. Instead, they believed horsetails
''Equisetum'' (; horsetail, snake grass, puzzlegrass) is the only living genus in Equisetaceae, a family of ferns, which reproduce by spores rather than seeds.
''Equisetum'' is a " living fossil", the only living genus of the entire subclass ...
, a common plant at the time containing the above characteristics, was probably an important food for the dinosaur. The results of the study were published online on June 30, 2009, in '' The Proceedings of the National Academy of Sciences'', the official journal of the United States National Academy of Sciences
The National Academy of Sciences (NAS) is a United States nonprofit, non-governmental organization. NAS is part of the National Academies of Sciences, Engineering, and Medicine, along with the National Academy of Engineering (NAE) and the Nati ...
. The study was published under the title, "Quantitative analysis of dental microwear in hadrosaurid dinosaurs, and the implications for hypotheses of jaw mechanics and feeding".
It was the first quantitative analysis of tooth microwear in dinosaurs. Purnell said the technique employed in the study was equally important as the findings themselves, and that the study proved analyzing microscopic scratch marks on teeth can provide reliable information about an animal's diet and chewing mechanism. Purnell said this method could be used to study other areas of scientific research, including the dietary habits of other long-vanished species including dinosaurs, extinct groups of fish or very early mammals. Purnell said the findings were further significant not only for the basic understanding of how hadrosaurids ate, but also because a lack of such understanding from those dinosaurs represented a "big gap in our knowledge" of the ecosystem of the late Cretaceous. Because hadrosaurs were the dominant terrestrial herbivores of that time, they played a major role in structure the ecosystem of the Late Cretaceous period. Purnell said, "The more we understand the ecosystems of the past, and how they were affected by global events like climate change, the better we can understand how changes now are going to pan out in the future." Lawrence Witmer, a paleontologist with Ohio University
Ohio University is a public research university in Athens, Ohio. The first university chartered by an Act of Congress and the first to be chartered in Ohio, the university was chartered in 1787 by the Congress of the Confederation and subseq ...
College of Osteopathic Medicine in Athens
Athens ( ; el, Αθήνα, Athína ; grc, Ἀθῆναι, Athênai (pl.) ) is both the capital and largest city of Greece. With a population close to four million, it is also the seventh largest city in the European Union. Athens dominates ...
, called the study, "One of the best microwear papers I've seen", although he said he was not yet convinced the hadrosaurid upper jaw could flex.
The hypothesis that hadrosaurs were likely grazers rather than browsers appears to contradict previous findings from preserved stomach contents found in the fossilized guts in previous hadrosaurs studies. In response to such findings, Purnell said preserved stomach contents are questionable because they do not necessarily represent the usual diet of the animal.[This information comes from the aforementioned Alan Boyle source from June 29, 2009. However, this specific information is not included in the body of the article, but rather a response by Boyle to comments in the article. Since the comments were written by Boyle himself, and since they cite information he received specifically from Purnell, they are as legitimate a source of information as the article itself.] Alan Boyle
Alan Boyle is an American journalist specializing in science and technology news. He worked for msnbc.com and NBC News Digital as science editor from 1996 to 2015. In 2015, he became aerospace and science editor for GeekWire. Boyle is also presi ...
, a journalist and MSNBC
MSNBC (originally the Microsoft National Broadcasting Company) is an American news-based pay television cable channel. It is owned by NBCUniversala subsidiary of Comcast. Headquartered in New York City, it provides news coverage and politi ...
science editor who reported on the team's findings, said of the apparent contradictions between Williams ''et al.''.'s study and previous stomach content findings are subject to debate, but do not necessarily render Williams ''et al.''.'s study irrelevant or incorrect. Specifically, Boyle said, "the claims about grazing vs. browsing are certainly not conclusive (but) the researcher's surmise is that they were more likely to graze". Williams ''et al.''.'s hypothesis of hadrosaurids as grazers who ate vegetation close to the ground, rather than browsing higher-growing leaves and twigs, would also contradict the portrayal of hadrosaurs in '' Jurassic Park'', the 1990 science fiction novel by Michael Crichton.
See also
* Timeline of hadrosaur research
A timeline is a display of a list of events in chronological order. It is typically a graphic design showing a long bar labelled with dates paralleling it, and usually contemporaneous events.
Timelines can use any suitable scale represent ...
Notes and references
External links
Downloadable version of 2008–2009 Purnell et al study
at '' The Proceedings of the National Academy of Sciences'' (official)
Press release about the 2008–2009 Purnell et al study
{{DEFAULTSORT:Hadrosaur Diet
Hadrosaurs
Eating behaviors