290:, 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
445:
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".
496:
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
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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
250:. 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
407:. 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.
278:, 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.
17:
230:. 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.
363:
182:
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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,
449:
553:
199:, 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
495:
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
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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
465:
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
111:
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
225:
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
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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
1781:
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
444:
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,
254:. 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
324:
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
428:
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
59:. 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.
266:
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
527:.'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
478:. 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
271:, 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.
66:, 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
752:
52:
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.
62:
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
531:.'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
301:, 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.
482:, 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
122:
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
1695:
492:. 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".
440:
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
221:
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
387:
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
1799:
484:
74:
66 million years ago. It has also remained unclear exactly what hadrosaurids ate. In particular, it has never been definitively proven whether hadrosaurs were
174:-like animal that browsed along rivers, using its forelimbs to manipulate branches. His vague inference of amphibious habits would later be expanded upon by
762:
345:
graduate student Justin S. Tweet found a homogeneous accumulation of millimeter-scale leaf fragments in the gut region of a well-preserved partially grown
489:
71:
919:(1856). "Notice of remains of extinct reptiles and fishes, discovered by Dr. F. V. Hayden in the Bad Lands of the Judith River, Nebraska Territories".
437:
to give high-power magnification of the scratches for study, and conducted a three-dimensional statistical analysis of the direction of the scratches.
309:
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
433:. 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
500:
507:, 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.
865:"The Paleobiological Implications of Herbivorous Dinosaur Coprolites from the Upper Cretaceous Two Medicine Formation of Montana: Why Eat Wood?"
1017:
832:
170:
of hadrosaurs, though. Of particular importance was the unequal lengths of the forelimbs and hindlimbs. He interpreted his new animal as a
1669:
1703:
591:; Weishampel, David B.; Forster, Catherine A. (2004). "Hadrosauridae". In Weishampel, David B.; Dodson, Peter; OsmĂłlska Halszka (eds.).
1590:"Quantitative analysis of dental microwear in hadrosaurid dinosaurs, and the implications for hypotheses of jaw mechanics and feeding"
258:(horsetails) as the major food source, as these plants existed in the same times and places as hadrosaurids, are known to be rich in
1377:
735:
608:
342:
178:, who contributed the mistaken conclusion that hadrosaur teeth and jaws were weak and suitable only for eating soft water plants.
1664:
189:
of hadrosaurs as semi-aquatic animals that could only chew soft water plants, a popular idea at the time which is now outdated
566:
396:
864:
1782:
information he received specifically from
Purnell, they are as legitimate a source of information as the article itself.
588:
434:
210:
274:
Lull and Wright added a new element to hadrosaurid feeding by proposing the presence of muscles analogous to mammalian
1503:
Tweet, Justin S.; Chin, Karen; Braman, Dennis R.; Murphy, Nate L. (2008). "Probable gut contents within a specimen of
159:
351:. As a result of that finding, Tweet concluded in September 2008 that the animal was likely a browser, not a grazer.
1555:"Plant-eating dinosaur spills his guts: Fossil suggests hadrosaur's last meal included lots of well-chewed leaves"
1826:
1554:
138:
The first hadrosaur finds did not include much skull material. Hadrosaur teeth have been known since the 1850s (
1008:
Creisler, Benjamin S. (2007). "Deciphering duckbills: a history in nomenclature". In
Carpenter Kenneth (ed.).
523:.'s study and previous stomach content findings are subject to debate, but do not necessarily render Williams
470:, which was normal for vegetation cropped close to the ground, or that it contained microscopic granules of
404:
326:
102:
251:
1061:(Dinosauria: Hadrosauridae): implications for latest Cretaceous megaherbivore diversity in North America"
519:
science editor who reported on the team's findings, said of the apparent contradictions between
Williams
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87:
49:
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193:
Cope described the next piece of the puzzle in 1874: a more complete jaw fragment in 1874 he named
175:
842:
247:
44:
remains a subject of debate among paleontologists, especially regarding whether hadrosaurids were
16:
1532:
1469:
Rybczynski, Natalia; Tirabasso, Alex; Bloskie, Paul; Cuthbertson, Robin; Holliday, Casey (2008).
1411:
1399:
1306:
1267:
1199:
1181:
892:
320:
243:
238:
The early study of hadrosaurid dietary adaptations and feeding behavior was summarized in a 1942
1036:(1874). "Report on the stratigraphy and Pliocene vertebrate paleontology of northern Colorado".
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657:
592:
558:
538:
56:
1794:
1507:(Dinosauria: Hadrosauridae) from the Upper Cretaceous Judith River Formation of Montana".
1423:
977:, from the Campanian of the East Coast of North America, with a reevaluation of the genus"
497:
471:
298:
263:
67:
21:
1605:
1520:
1245:
1169:
1076:
880:
653:
286:
The general preexisting consensus on hadrosaurid paleobiology was challenged in 1964 by
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79:
1470:
1815:
1536:
1310:
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368:
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part of the skull, which was drawn out, long, and wide. He compared it to that of a
107:
1758:"Duck-billed dentistry: evidence for hadrosaur diet from tooth microwear (Abstract)"
1403:
896:
383:
on vegetation close to the ground and had a way of chewing unlike any modern animal.
105:
researchers analyzed hundreds of microscopic scratches on the teeth of a fossilized
1757:
1262:
941:
916:
677:
504:
400:
388:
314:
291:
167:
166:-like skull) Leidy had enough skeletal material to make other inferences about the
139:
127:
416:, a hadrosaurid that lived between 68 and 66 million years ago in what is now the
1085:
333:
believe
Weishampel's model may not be viable, and plan to test other hypotheses.
1735:
633:
373:
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287:
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29:
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888:
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119:
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1012:. Bloomington and Indianapolis: Indiana University Press. pp. 185–210.
479:
467:
453:
239:
201:
144:
115:
37:
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1104:
448:
112:
and sideways while chewing, as the lower jaw slid against the upper teeth.
1395:
662:
637:
410:
Williams, Barrett, and
Purnell conducted their study using the jaws of an
366:
Researchers studied microscopic scratches on the fossilized jawbone of an
376:
318:
largely unproven until the study by Purnell, Williams and Barrett, which
218:
195:
171:
123:
33:
1302:
971:
Prieto-Márquez, Alberto; Weishampel, David B.; Horner, John R. (2006).
753:"Duck-Billed Dinosaur's Shifting Teeth Were Like a "Cranial Cuisinart""
380:
95:
75:
45:
1562:
638:"A reconsideration of the paleoecology of the hadrosaurian dinosaurs"
430:
421:
392:
294:
259:
163:
83:
63:
1149:
148:), and a few fragments of teeth and jaws were among the bones named
1364:. Vol. 87. Berlin; New York: Springer-Verlag. pp. 1–109.
1038:
U.S. Geological and Geographical Survey of the Territories Bulletin
599:(2nd ed.). Berkeley: University of California Press. pp.
1762:
Transactions of the Leicester Literary & Philosophical Society
948:, a new saurian from the Cretaceous of New jersey, related to the
837:
699:
Galton, Peter M. (1973). "The cheeks of ornithischian dinosaurs".
516:
475:
447:
361:
268:
214:
180:
15:
1588:
Williams, Vincent S.; Barrett, Paul M.; Purnell, Mark A. (2009).
511:
they do not necessarily represent the usual diet of the animal.
91:
55:
The mouth of a hadrosaur had hundreds of tiny teeth packed into
1121:(1883). "On the characters of the skull in the Hadrosauridae".
403:, a British paleontologist from the geology department of the
954:
Proceedings of the Academy of Natural Sciences of Philadelphia
921:
Proceedings of the Academy of Natural Sciences of Philadelphia
730:. Berkeley: University of California Press. pp. 614–626.
726:
Fastovsky, D.E; Smith, J.B (2004). "Dinosaur paleoecology".
1123:
Proceedings of the Philadelphia Academy of Natural Sciences
1670:
PlanetEarth Online (Natural Environment Research Council)
78:
who ate vegetation close to the ground, like modern-day
583:
581:
90:
who ate higher-growing leaves and twigs, like today's
1807:
Press release about the 2008–2009 Purnell et al study
1795:
Downloadable version of 2008–2009 Purnell et al study
1010:
Horns and Beaks: Ceratopsian and Ornithopod Dinosaurs
1800:
The Proceedings of the National Academy of Sciences
485:
The Proceedings of the National Academy of Sciences
1355:Evolution in jaw mechanics in ornithopod dinosaurs
1336:Lull, Richard Swann; and Wright, Nelda E. (1942).
1323:Lull, Richard Swann; and Wright, Nelda E. (1942).
1777:
1775:
1359:Advances in Anatomy, Embryology, and Cell Biology
680:(1970). "The posture of hadrosaurian dinosaurs".
70:ecosystems and how they were affected during the
1594:Proceedings of the National Academy of Sciences
1475:(Hadrosauridae) for testing chewing hypotheses"
154:by Leidy in 1858. (The skeletal mount made for
1724:
1722:
1720:
1659:
1657:
1655:
1653:
1651:
1649:
1647:
1645:
1643:
1206:. Geological Society of America Special Paper
1055:Campione, Nicolás E.; Evans, David C. (2011).
355:2008–2009 hadrosaur chewing study by Williams
48:who fed on vegetation close to the ground, or
1548:
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8:
1583:
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1579:
1210:. Geological Society of America. p. 43.
823:
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788:"Hadrosaur chowdown — grind, grind, grind".
1731:"Study hints at what and how dinosaurs ate"
817:
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130:, all of which would have been nutritious.
32:, also commonly referred to as duck-billed
490:United States National Academy of Sciences
1623:
1613:
1261:
1094:
1084:
661:
209:. Cope immediately drew attention to the
1696:"Dinosaur teeth "hold secret to eating""
1471:"A three-dimensional animation model of
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1136:
1003:
1001:
999:
997:
783:
781:
779:
1756:Williams, Vince; Purnell, Mark (2008).
1338:Hadrosaurian Dinosaurs of North America
1325:Hadrosaurian Dinosaurs of North America
1204:Hadrosaurian Dinosaurs of North America
936:
934:
628:
626:
624:
622:
620:
577:
337:2008 preserved stomach content findings
1665:"Teeth scratches reveal dinosaur menu"
1419:
1409:
36:or hadrosaurs, were large terrestrial
1285:Kräusel, R. (1922). "Die Nahrung von
72:Cretaceous–Paleogene extinction event
7:
537:, the 1990 science fiction novel by
118:(fossilized droppings) of some Late
1440:"Into the Mouth of the Hadrosaur".
305:1984 hadrosaurid chewing hypothesis
713:10.1111/j.1502-3931.1973.tb00873.x
14:
1057:"Cranial growth and variation in
343:University of Colorado at Boulder
751:Strickland, Eliza (2009-06-30).
551:
86:, or whether the dinosaurs were
501:College of Osteopathic Medicine
372:(pictured), and concluded that
567:Timeline of hadrosaur research
488:, the official journal of the
1:
1729:Bryner, Jeanna (2009-06-29).
984:Acta Palaeontologica Polonica
42:diet of hadrosaurid dinosaurs
1702:. 2009-06-30. Archived from
1673:. 2009-06-30. Archived from
1505:Brachylophosaurus canadensis
1291:Paläontologische Zeitschrift
1086:10.1371/journal.pone.0025186
435:scanning electron microscope
329:animation model. Rybczynski
1553:Lloyd, Robin (2008-09-25).
1234:American Journal of Science
1202:; Wright, Nelda E. (1942).
1158:American Journal of Science
863:Chin, K. (September 2007).
642:American Journal of Science
282:Ostrom (1964) and reception
160:Benjamin Waterhouse Hawkins
1843:
1529:10.2110/palo.2007.p07-044r
1479:Palaeontologia Electronica
889:10.2110/palo.2006.p06-087r
1450:(5937): 129. 2009-07-10.
1370:10.1007/978-3-642-69533-9
1254:10.2475/ajs.s3-44.262.343
1224:(1892). "Restorations of
134:Early history of research
1456:10.1126/science.325_129d
1178:10.2475/ajs.s3-45.265.83
1150:"The skull and brain of
1615:10.1073/pnas.0812631106
1485:(2): online publication
1263:2027/hvd.32044107356040
682:Journal of Paleontology
405:University of Leicester
341:In 2008, a team led by
262:, and contain abrasive
252:grasses were for horses
217:in side view, and to a
162:included a speculative
103:University of Leicester
1222:Marsh, Othniel Charles
833:"How dinosaurs chewed"
462:
397:Natural History Museum
384:
234:Lull and Wright (1942)
219:short-billed spoonbill
190:
26:
25:, a crested hadrosaur.
663:10.2475/ajs.262.8.975
474:, which is common in
451:
365:
228:Othniel Charles Marsh
205:, it is now known as
185:Early restoration by
184:
101:A 2008–2009 study by
19:
1351:Weishampel, David B.
1034:Cope, Edward Drinker
573:Notes and references
1606:2009PNAS..10611194W
1600:(27): 11194–11199.
1565:on February 4, 2016
1521:2008Palai..23..624T
1246:1892AmJS...44..343M
1200:Lull, Richard Swann
1170:1893AmJS...45...83M
1077:2011PLoSO...625186C
975:Hadrosaurus foulkii
946:Hadrosaurus foulkii
881:2007Palai..22..554C
654:1964AmJS..262..975O
515:, a journalist and
459:Equisetum telmateia
202:Diclonius mirabilis
176:Edward Drinker Cope
1303:10.1007/BF03041547
463:
385:
244:Richard Swann Lull
191:
27:
1146:Marsh, Othniel C.
1019:978-0-253-34817-3
348:Brachylophosaurus
327:three-dimensional
196:Cionodon arctatus
187:Charles R. Knight
1834:
1827:Eating behaviors
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1561:. Archived from
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1240:(262): 343–349.
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841:. Archived from
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424:. The specific
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68:Late Cretaceous
22:Parasaurolophus
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30:Hadrosaurids
28:
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1736:LiveScience
1327:. p. 30–36.
990:(1): 77–98.
829:Boyle, Alan
374:duck-billed
315:bird-hipped
311:ornithopods
288:John Ostrom
156:Hadrosaurus
151:Hadrosaurus
1822:Hadrosaurs
1816:Categories
1803:(official)
1742:2009-07-03
1710:2009-07-03
1681:2009-07-03
1569:2009-07-03
1489:2008-08-10
1226:Claosaurus
1152:Claosaurus
960:: 213–218.
902:2008-09-10
849:2009-07-03
769:2009-07-03
513:Alan Boyle
480:horsetails
452:An extant
297:along the
120:Cretaceous
116:Coprolites
38:herbivores
1537:131393649
1422:ignored (
1412:cite book
1388:0301-5556
1311:186239385
1287:Trachodon
1272:130216318
1186:131740074
1129:: 97–107.
950:Iguanodon
944:(1858). "
454:horsetail
377:dinosaurs
240:monograph
223:Diclonius
145:Trachodon
34:dinosaurs
1768:: 58–59.
1634:19564603
1559:NBC News
1404:12547312
1353:(1984).
1148:(1893).
1105:21969872
1065:PLOS ONE
927:: 72–73.
897:86197149
758:Discover
636:(1964).
545:See also
292:ossified
211:anterior
172:kangaroo
126:-eating
124:detritus
96:giraffes
88:browsers
50:browsers
1625:2708679
1602:Bibcode
1517:Bibcode
1509:PALAIOS
1443:Science
1396:6464809
1242:Bibcode
1166:Bibcode
1096:3182183
1073:Bibcode
1044:: 9–28.
877:Bibcode
869:PALAIOS
701:Lethaia
650:Bibcode
379:likely
321:Science
295:tendons
76:grazers
64:mammals
46:grazers
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521:et al.
505:Athens
472:silica
422:Canada
399:; and
393:London
381:grazed
357:et al.
331:et al.
264:silica
260:starch
164:iguana
40:. The
1533:S2CID
1400:S2CID
1307:S2CID
1268:S2CID
1182:S2CID
980:(PDF)
893:S2CID
838:MSNBC
517:MSNBC
476:grass
391:with
269:moose
215:goose
80:sheep
1630:PMID
1424:help
1392:PMID
1384:ISSN
1374:ISBN
1228:and
1101:PMID
1014:ISBN
732:ISBN
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468:grit
420:and
246:and
92:deer
84:cows
1797:at
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1620:PMC
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