Parasaurolophus

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Parasaurolophus
Parasaurolophus cyrtocristatus in the Field Museum of Natural History in Chicago.

Parasaurolophus cyrtocristatus in the Field Museum of Natural History in Chicago .

Temporal occurrence
Upper Cretaceous (late Campanium )
76.4 to 72 million years
Locations
Systematics
Pelvic dinosaur (Ornithischia)
Ornithopoda
Iguanodontia
Hadrosaurs (Hadrosauridae)
Lambeosaurinae
Parasaurolophus
Scientific name
Parasaurolophus
Parks , 1922
species
  • Parasaurolophus walkeri Parks, 1922 ( type )
  • Parasaurolophus tubicen Wiman, 1931
  • Parasaurolophus cyrtocristatus Ostrom, 1961

Parasaurolophus is a genus of dinosaurs from the group of hadrosaurs , which is part of the Ornithischia (bird's pelvis dinosaur). Finds of these animals come from rock layers of the Upper Cretaceous (late Campanium ) in Alberta ( Canada ), Utah and New Mexico ( USA ). Like all hadrosaurs, the herbivores could probably move two-legged and four-legged and had the characteristic toothless “duck bill” and molars in their jaws. The most noticeable feature is the headdress, a long, rearward-facing bone peg. Due to its striking appearance, Parasaurolophus is one of the better-known representatives of the dinosaurs.

description

Parasaurolophus walkeri in size comparison with a human

In contrast to some other hadrosaurs , which are often received in popular science, relatively few Parasaurolophus specimens have been found, which means that the skeleton is not fully known. The holotype specimen of Parasaurolophus walkeri is estimated to be 9.5 m in length, with the skull together with the bone plug being about 1.6 m. The skull and cones of the holotype specimen of Parasaurolophus tubicen measure 2 m. The weight of the living animal was about 2.5 tons. The only known foreleg is relatively short compared to other hadrosaurids, with the shoulder blades short but wide. The thighbone (femur) of Parasaurolophus walkeri is 103 cm long and quite robust for its length. The shoulder area and the pelvic bones were also quite heavy.

Like other lambeosaurines, Parasaurolophus had high spinous processes that significantly raised the back and the base of the tail. The spinous processes reached their highest point above the hips. Of Parasaurolophus walkeri skin prints are furthermore known, the uniform tuberkelähnliche shed, but have no larger structures.

Drawing life reconstruction of Parasaurolophus walkeri

The most striking feature of the genus was the bone plug on the skull. This is a long tube that protruded backwards over the head and was formed from the nasal bone and the intermaxillary bone (premaxillary). The cone of bone was mostly hollow, but tubes ran from the nostrils to the end, curved and led back into the skull. While these tubes were built comparatively simply in Parasaurolophus walkeri , the structure in Parasaurolophus tubicen was more complicated. In this species the tubes showed labyrinthine splits, confluences and dead ends.

In the holotype skeleton of Parasaurolophus walkeri , an indentation was found in the vertebral processes at the point where the bone plug would have touched the back. There was speculation after the animal placed its bone plug in this notch while running. However, this feature is probably due to pathology and a peculiarity of this individual. William Parks , who first described the animal, postulated ligaments or muscles that should run from the end of the bone peg to the vertebrae in the area of ​​the notch to support the head. This seems unlikely, however - a holdover from this idea is a flap of skin that is stretched between the bone cone and the back in some reconstructions. According to some illustrators, this hypothetical flap of skin and the raised back were colored brightly for the purpose of identifying the species or for courtship.

Systematics and types

Skull of Parasaurolophus cyrtocristatus in the Field Museum of Natural History

Within the Hadrosauridae Parasaurolophus is counted to the Lambeosaurinen, although it was initially considered a close relative of the Hadrosaurinen Saurolophus . Parasaurolophus' closest relative may have been Charonosaurus from the Amur region of northeast China. Charonosaurus has a skull similar to that of Parasaurolophus , but the bone cone is only incomplete. The close relationship of these genera is tied to common features ( synapomorphies ) on the skull and leg bones; For example, the paired frontal bone formed a platform to support the bone peg that extended over parts of the supratemporal window . In contrast to Charonosaurus , however , Parasaurolophus showed, for example, a sagittal ridge on the parietal bone (parietal). Parasaurolophus and Charonosaurus are grouped together within the Lambeosaurinae as Parasaurolophini and compared to the sister group Lambeosaurini , which includes all other Lambeosaurines.

So far, three species of the genus Parasaurolophus have been described:

Of the type species Parasaurolophus walkeri (Parks, 1922) from Alberta , a single skeleton with a complete skull is known. This species differed from Parasaurolophus tubicen by the simpler tubular structure of the bone cone; in contrast to Parasaurolophus cyrtocristatus , it had a long bone cone that was not bent downwards. In contrast to all other lambeosaurines, apart from Parasaurolophus cyrtocristatus , Parasaurolophus walkeri also showed a deeper neck of the prepubis and longer upper arm bones ( humerus ) than forearms.

Parasaurolophus tubicen (Wiman, 1931) from the Kirtland Formation in New Mexico is known from finds of at least three individuals. It was the largest species, had more complex tubes in the bone cone than Parasaurolophus walkeri, and had a longer and straighter bone cone than Parasaurolophus cyrtocristatus .

Parasaurolophus cyrtocristatus (Ostrom, 1961) was also found in New Mexico ( Fruitland Formation ) and the Kaiparowits Formation in Utah . Three possible finds are known. It was the smallest type and was characterized by a short and rounded bone cone. This led to the hypothesis that it could be a female or cub of Parasaurolophus tubicen . Lastly, this idea was advocated by Thomas Williamson, who notes that Parasaurolophus cyrtocristatus is approximately 72% the size of Parasaurolophus tubicen , which is roughly the same size ratio that is assumed in other Lambeosaurinae between adult animals and young animals that are beginning to develop marked sexual dimorphism becomes. However, in recent papers this view has been rejected. Alternatively, the other two species could have been more closely related to each other than Parasaurolophus cyrtocristatus , which causes the size variation of this species.

A cranial skull from a young animal from Dinosaur Provincial Park in Alberta could not be assigned to an existing species. Three other finds from Alberta can possibly also be attributed to Parasaurolophus .

Paleobiology

Habitat

Gorgosaurus attacks Parasaurolophus cyrtocristatus

Parasaurolophus walkeri from the Dinosaur Park Formation of Alberta was part of a rich and well-documented dinosaur fauna that Ceratopsier (Horn dinosaurs) as Centrosaurus , Styracosaurus and Chasmosaurus , more hadrosaur as prosaurolophus , gryposaurus , Corythosaurus and Lambeosaurus , Ankylosaurier (armored dinosaurs) as Edmontonia and Euoplocephalus as well as the tyrannosaurid Gorgosaurus . It was a rare part of this fauna. The landscape was probably crossed by rivers and marshy floodplains and the climate was influenced by the marine environment of the Western Interior Seaway . The climate was warmer than present-day Alberta, with no frost in winter, but with wet and dry seasons. The flora consisted of conifers , which formed the canopy, as well as ferns , tree ferns , and coversamers .

The species from the Kirtland Formation in New Mexico, on the other hand, lived together with the large sauropod Alamosaurus , the hadrosaur Kritosaurus , the ceratopsian Pentaceratops , the ankylosaur Nodocephalosaurus , the small theropod Saurornitholestes and so far unspecified tyrannosaurids. The sediments of the Kirtland Formation likely represent a flood plain that arose after the retreat of the Western Interior Seaway. Conifers dominated the flora, and chasmosaurine ceratopier (a group of horned dinosaurs) appeared to be more common than hadrosaurids.

Diet

As a member of the Hadrosauridae, Parasaurolophus was a large herbivore capable of both four-legged and two-legged walking , with advanced jaws that allowed chewing movements. The chewing strips formed so-called tooth batteries, in which several hundred teeth were arranged, with only a handful being used at a time. Worn teeth were constantly being replaced. Plant material was first plucked with the beak and then held in cheek-like mouth areas. They could probably graze from the bottom up to four meters high. Paleontologist Bob Bakker said Lambeosaurinae have narrower snouts than Hadrosaurinae, the other subfamily of the Hadrosauridae. This led to the theory that Lambeosaurinae were more picky eaters than their broad-billed, mostly combless counterparts.

Bone cones

Numerous hypotheses have been proposed to explain the function of the bone plug, but most have been rejected. Today one suspects several functions: visual functions (identification of species and gender), effect as a resonance body for calls for communication, and temperature regulation. However, it is not clear which function was the most important at what time in evolution.

Differences between species and ages

Comparison of the bone cones of Parasaurolophus cyrtocristatus (A) and Parasaurolophus walkeri (B)

As with other lambeosaurines, it is assumed that the head names change with age and are different in males and females (sexual dimorphism) with Parasaurolophus .

James Hopson, one of the first researchers to describe the ornaments of lambeosaurins in relation to these differences, suggested that Parasaurolophus cyrtocristatus , the smaller species with the short, rounded bone cone, was a female. Thomas Williamson, meanwhile, said it was a young Parasaurolophus tubicen . Other researchers, however, see Parasaurolophus cyrtocristatus as an independent species. None of these ideas was largely accepted - since only six skulls and one brain skull of a young animal are known, only further findings will probably bring clarity.

Williamson suspects that the young had small ornaments, the growth of which accelerated in the period immediately before sexual maturity. A new study of the cranial skull of a juvenile previously attributed to Lambeosaurus but now attributed to Parasaurolophus suggests a small crest in juvenile animals. The find shows a small bulge formed by the pair of frontal bones . A similar structure is also known from the fossils of adult animals, only much larger there - here the frontal bones form a platform that supports the base of the bone peg.

Refuted hypotheses about function

Skull of Parasaurolophus walkeri in the Natural History Museum , London

In the past there have been numerous hypotheses that attempted to explain the function of the bone plug. In the past, many researchers assumed that the hypothesis that hadrosaurs were amphibious until the 1960s was an adaptation to an aquatic way of life. For example, Alfred Sherwood Romer (1933) suggested a snorkel-like function of the bone plug, while Martin Wilfarth (1947) considered a function as a holder for a trunk, which should have been used for breathing and for collecting food. Charles M. Sternberg (1935), on the other hand, assumed that it was a device for keeping water out of the lungs with air, and Ned Colbert (1945) suggested that the hollow bone plug served as an air reservoir to enable longer dives.

Other assumptions were more physical. As already mentioned above, the first descriptor William Parks believed in a ligament that connected the end of the bone cone to the vertebrae - to stabilize the head. Othenio Abel thought the bone plug was a weapon used in fights between two rival Parasaurolophus , and Angela Milner said it could have been used to push the vegetation aside in the thicket, as today's cassowary does with his helmet. Further interpretations are e.g. B. Teresa Maryańska and Halszka Osmólska , who believed that the bone cone harbored salt glands, or John Ostrom , who, given the animal's lack of defensive capabilities, suspected olfactory tissue, which should give the animals a better sense of smell.

Most of these hypotheses have fallen into disrepute over time. So there was B. neither a hole, which was necessary for a snorkeling function, nor approaches for the muscles of a trunk, which anyway would have little sense in an animal equipped with a beak. The available space was far too insignificant as an air reservoir, and other hadrosaurs also had large heads without having to support them with ligaments. The olfactory nerves and olfactory cells were also outside the bone cone, which shows that the latter cannot have anything to do with the sense of smell. On the other hand, these hypotheses do not explain why the bone cone had exactly this shape or why other lambeosaurines had completely different constructions on their heads. Instead, the researchers are focusing on visual and auditory functions.

Visual functions

Live reconstruction of Parasaurolophus walkeri

As a large object, the bone plug could be used as a visual signal. The animals' eyes were quite large and had scleral rings , suggesting that the animals were diurnal and that their sense of sight was very important. As is also suspected with other lambeosaurins, two visual functions of the bone cone were probably given: On the one hand, the function as a distinguishing feature so that the animals could differentiate conspecifics from other hadrosaur species (e.g. Lambeosaurus or Corythosaurus ), and on the one hand on the other hand that for sexual identification - possibly for courtship and to impress rivals - similar to the recent deer . However, these functions do not explain the complexity of the ducts inside the bone plug, which is why there must have been another function.

Function as a sound box

Carl Wiman was the first to propose a sound signal function for the ducts (1931) - and compared the bone plug with a crumhorn . Hopson and David B. Weishampel took up this idea again in the 1970s and 1980s. Hopson found evidence of sensitive hearing in hadrosaurids: For example, a stirrup (an ossicle) was discovered in the related Corythosaurus , which, in combination with a large space for the eardrum, indicates a sensitive middle ear . Furthermore, like crocodiles , the lagena is elongated, which indicates a well-developed inner ear . Weishampel predicted that Parasaurolophus walkeri would have been able to produce frequencies of 48 to 240 Hz with the help of the bone plug; for Parasaurolophus cyrtocristatus he gave 75 to 375 Hz. He also said - based on the similarities of the inner ear with that of crocodiles - adult hadrosaurids are sensitive to the high frequencies that young animals may have produced.

A well-preserved skull of Parasaurolophus tubicen was modeled on the computer and, based on the 3D model, the possible sound of the animal, a foghorn-like sound, was reconstructed. This species has an even greater complexity in the structure of the bone cone than Parasaurolophus walkeri , the main part of the bone cone produces tones of about 30 Hz.

Function for cooling

Another theory is that it is a temperature control device . This idea, first proposed in 1978, has been a hot topic again since the 1990s. PE Wheeler first said that the bone plug was a means of cooling the brain. Around the same time, the idea of ​​temperature regulation by the bone plug appeared in a paper by Maryańska and Osmólska. The theory received further attention in a paper by Sullivan and Willamson on this genus. The large surface area and blood vessels in the bone cone are cited as indicators. In a discussion by David Evans (2006) about the functions of the Lambeosaurinae combs, he favored the idea.

Discovery story

The first find was made in 1920 as part of an expedition by the University of Toronto in Sand Creek on the Red Deer River in Alberta, Canada. The rock layer is known today as the Dinosaur Park Formation and contains fossils from the Campanium. The specimen (holotype; copy number ROM 768) consists of a partial skeleton with a skull, with the leg bones below the knee joints and most of the tail missing.

Parasaurolophus walkeri skeleton in the Ewolucji Polskiej Akademii Nauk Museum in Warsaw

In 1922 , William Parks described the new animal as Parasaurolophus walkeri . Parks named the genus Parasaurolophus , which means something like "almost a comb lizard " ( Greek sauros - lizard, lophos - comb), because he thought Saurolophus was a close relative. The epithet walkeri honors Sir Byron Edmund Walker, a Chairman of the Board of Trustees of the Royal Ontario Museum . However, Parasaurolophus finds from Alberta remained rare - only three other finds without skulls from the Dinosaur Park Formation are known, which may belong to Parasaurolophus . In 2007 the skull of a young animal (specimen number CMN 8502) was re-examined and assigned to this genus. This find, which probably came from the Dinosaur Park Formation, was already collected in 1917 by Charles Mortram Sternberg and in 1924 by Gilmore as Lambeosaurus sp. described.

In 1921, Charles Hazelius Sternberg discovered a fragmentary skull (copy number PMU.R1250) in the somewhat younger Kirtland Formation in San Juan Country (New Mexico), which was sent to Uppsala ( Sweden ) for further investigation . In 1931 Carl Wiman described it as a second species, Parasaurolophus tubicen . The Artepitheth tubicen is derived from the Latin tǔbǐcěn and means "trumpeter". A second, almost complete skull of Parasaurolophus tubicen (specimen number NMMNH P-25100) was discovered in New Mexico in 1995. This skull was examined in 1999 using computed tomography and, among other things, offered insights into the functioning of the bone plug.

John Ostrom described another good find (specimen number FMNH P27393) from New Mexico in 1961 as Parasaurolophus cyrtocristatus . The specimen now in the Field Museum of Natural History consists of an incomplete skull with a short, rounded bone spigot, as well as most of the postcranial skeleton (the residual skeleton that adjoins the skull). The feet, the neck and parts of the tail are missing. The species name is derived from the Latin words curtus - "shortened" and cristatus - "comb-bearing". The skeleton was found either in the top of the Fruitland Formation or, more likely, in the Kirtland Formation above. 1979 the species was also detected in Utah: David B. Weishampel and James A. Jensen described an incomplete skull (copy number BYU 2467) with a similarly short bone plug from the layers of the Kaiparowits Formation , Garfield County . In 1999, another Utah skull with short and rounded bone cones was described. A skeleton of a juvenile , not even a year old, described in 2013 shows only a small bone crest.

In popular culture

With its spectacular horn cones, Parasaurolophus has appeared in many films and television shows. One example is the children's film series “ In a Land Before Time” (The Land Before Time), in which the character “Ducky” is officially considered a Parasaurolophus , even though she is a Saurolophus . This dinosaur also appears in the background of many films, such as in the section “Le sacre du Printemps” from Disney's “ Fantasia ”, all three “ Jurassic Park ” films and Disney's “Dinosaurs”. Furthermore, Parasaurolophus has often been found as a dinosaur toy for decades, e.g. B. from "Louis Marx and Company", "MPC", "Battat", "Hancock" or the Carnegie collection.

Web links

Commons : Parasaurolophus  - Collection of images, videos and audio files

Individual evidence

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  3. ^ Richard S. Lull , Nelda E. Wright: Hadrosaurian Dinosaurs of North America (= Geological Society of America. Special Papers. Vol. 40, ISSN  0072-1077 ). Geological Society of America, New York NY 1942, p. 229.
  4. ↑ a b c d e Donald F. Glut : Parasaurolophus. In: Donald F. Glut: Dinosaurs. The Encyclopedia. McFarland & Co, Jefferson NC et al. 1997, ISBN 0-89950-917-7 , pp. 678-684.
  5. ^ A b c Richard S. Lull, Nelda E. Wright: Hadrosaurian Dinosaurs of North America (= Geological Society of America. Special Papers. Vol. 40, ISSN  0072-1077 ). Geological Society of America, New York NY 1942, pp. 209-213.
  6. ↑ Michael K. Brett-Surman, Jonathan R. Wagner: Appendicular anatomy in Campanian and Maastrichtian North American hadrosaurids. In: Kenneth Carpenter (Ed.): Horns and Beaks. Ceratopsian and ornithopod Dinosaurs. Indiana University Press, Bloomington IN 2007, ISBN 978-0-253-34817-3 , pp. 135-169.
  7. ^ A b c d e William A. Parks : Parasaurolophus Walkeri. A new genus and species of crested Trachodont dinosaur (= University of Toronto Studies. Geology Series. Vol. 13, ISSN  0372-4913 ). University of Toronto - University Library, Toronto 1922, digitized .
  8. ↑ a b c d e Robert M. Sullivan, Thomas E. Williamson: A new skull of Parasaurolophus (Dinosauria: Hadrosauridae) from the Kirtland Formation of New Mexico and a revision of the genus (= New Mexico Museum of Natural History and Science. Bulletin 15, ISSN  1524-4156 ). New Mexico Museum of Natural History and Science, Albuquerque NM 1999, digitized .
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  12. ↑ Pascal Godefroit, Shuqin Zan, Liyong Jin: Charonosaurus jiayinensis ng, n.sp., a lambeosaurine dinosaur from the Late Maastrichtian of northeastern China. In: Comptes Rendus de l'Académie des Sciences. Series 2, Fascicule A: Sciences de la Terre et des Planètes. Vol. 330, No. 12, 2000, ISSN  0764-4450 , pp. 875-882, doi : 10.1016 / S1251-8050 (00) 00214-7 .
  13. ↑ a b c d David C. Evans, Robert R. Reisz, Kevin Dupuis: A juvenile Parasaurolophus (Ornithischia: Hadrosauridae) Braincase from Dinosaur Provincial Park, Alberta, with comments on crest ontogeny in the genus. In: Journal of Vertebrate Paleontology. Vol. 27, No. 3, 2007, ISSN  0272-4634 , pp. 642-650, doi : 10.1671 / 0272-4634 (2007) 27 [642: AJPOHB] 2.0.CO; 2 .
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  16. ↑ a b c d Thomas E. Williamson: Review of Hadrosauridae (Dinosauria, Ornithischia) from the San Juan Basin, New Mexico. In: Spencer G. Lucas, Andrew B. Heckert (eds.): Dinosaurs of New Mexico (= New Mexico Museum of Natural History and Science. Bulletin. 17). New Mexico Museum of Natural History and Science, Albuquerque NM 2000, pp. 191-213, online .
  17. ^ A b David A. Eberth: The Geology. In: Philip J. Currie , Eva B. Koppelhus (Eds.): Dinosaur Provincial Park. A spectacular ancient ecosystem revealed. Indiana University Press, Bloomington IN et al. 2005, ISBN 0-253-34595-2 , pp. 54-82.
  18. ^ A b David B. Weishampel, Paul M. Barrett , Rodolfo Coria , Jean Le Loeuff, Xing Xu , Xijin Zhao , Ashok Sahni, Elizabeth Gomani, Christopher R. Noto: Dinosaur distribution. In: David B. Weishampel, Peter Dodson, Halszka Osmólska (eds.): The Dinosauria. 2nd edition. University of California Press, Berkeley CA et al. 2004, ISBN 0-520-24209-2 , pp. 517-683, here pp. 517-606.
  19. ↑ a b Michael J. Ryan, David C. Evans: Ornithischian Dinosaurs. In: Philip J. Currie , Eva B. Koppelhus (Eds.): Dinosaur Provincial Park. A Spectacular Ancient Ecosystem Revealed. Indiana University Press, Bloomington IN et al. 2005, ISBN 0-253-34595-2 , pp. 312-348.
  20. ^ Dennis R. Braman, Eva B. Koppelhus (ed.): Campanian palynomorphs. In: Philip J. Currie, Eva B. Koppelhus (Eds.): Dinosaur Provincial Park. A spectacular ancient ecosystem revealed. Indiana University Press, Bloomington IN et al. 2005, ISBN 0-253-34595-2 , pp. 101-130.
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  24. ↑ a b c d David C. Evans: Nasal cavity homologies and cranial crest function in lambeosaurine dinosaurs. In: Paleobiology. Vol. 32, No. 1, 2006, pp. 109-125, doi : 10.1666 / 0094-8373 (2006) 032 [0109: NCHACC] 2.0.CO; 2 .
  25. ^ Alfred Sherwood Romer : Vertebrate Paleontology. University of Chicago Press, Chicago IL 1933, p. 491.
  26. ↑ Martin Wilfarth: Trunk-bearing dinosaurs. In: Orion. Illustrated magazine for nature and technology. Vol. 2, 1947, ZDB -ID 207436-9 , pp. 525-532.
  27. ^ Charles M. Sternberg: Hooded Hadrosaurs of the Belly River series of the Upper Cretaceous (= National Museum of Canada. Geological Series. Bulletin. 52, ZDB -ID 429579-1 = National Museum of Canada. Bulletin. 77). Patenaude, Ottawa 1935.
  28. ^ Edwin H. Colbert : The Dinosaur Book. The ruling Reptiles and their Relatives (= Man and Nature Publications. Handbook. No. 14). The American Museum of Natural History, New York NY 1945, digitized .
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  30. ^ Teresa Maryańska, Halszka Osmólska: Aspects of hadrosaurian cranial anatomy. In: Lethaia. Vol. 12, No. 3, 1979, ISSN  0024-1164 , pp. 265-273, doi : 10.1111 / j.1502-3931.1979.tb01006.x .
  31. ↑ John H. Ostrom : The cranial crests of hadrosaurian dinosaurs. In: Postilla. Vol. 62, 1962, ISSN  0079-4295 , pp. 1-29.
  32. ↑ a b Carl Wiman : Parasaurolophus tubicen n. Sp. from the chalk in New Mexico (= Nova Acta Regiae Societatis Scientiarum Upsaliensis. Series 4, Vol. 7, No. 5, ZDB -ID 210356-4 ). Almqvist & Wiksell, Uppsala 1931.
  33. ^ A b David B. Weishampel: Acoustic analyzes of potential vocalization in lambeosaurine dinosaurs (Reptilia: Ornithischia). In: Paleobiology. Vol. 7, No. 2, 1981, pp. 252-261.
  34. ↑ David B. Weishampel: The nasal cavity of lambeosaurine hadrosaurids (Reptilia; Ornithischia); comparative anatomy and homologies. In: Journal of Paleontology. Vol. 55, No. 5, 1981, pp. 1046-1057.
  35. ^ Sandia National Laboratories: Scientists Use Digital Paleontology to Produce Voice of Parasaurolophus Dinosaur. December 5, 1997, archived from the original on August 17, 2014 ; Retrieved October 24, 2014 .
  36. ↑ Carl F. Diegert, Thomas E. Williamson: A digital acoustic model of the Lambeosaurine hadrosaur Parasaurolophus tubicen. In: Journal of Vertebrate Paleontology. Vol. 18, Supplement to No. 3 = Abstracts of Papers Fifty-Eighth Annual Meeting, Society of Vertebrate Paleontology, Snowbird Ski and Summer Resort Snowbird, Utah, September 30 - October 3, 1998 , 1998, p. 38A.
  37. ^ PE Wheeler: Elaborate CNS cooling structures in large dinosaurs. In: Nature . Vol. 275, No. 5679, 1978, pp. 441-443, doi : 10.1038 / 275441a0 .
  38. ↑ Robert M. Sullivan, Thomas E. Williamson: A new skull of Parasaurolophus (long-crested form) from New Mexico: external and internal (CT scans) features and their functional implications. In: Journal of Vertebrate Paleontology. Vol. 16, Supplement to No. 3 = Abstracts of Papers Fifty-Sixth Annual Meeting, Society of Vertebrate Paleontology, American Museum of Natural History, New York, New York, October 16-19, 1996 , 1996, p. 68A.
  39. ^ Philip J. Currie, Dale A. Russell: Geographic and stratigraphic distribution of dinosaur remains. In: Philip J. Currie, Eva B. Koppelhus (Eds.): Dinosaur Provincial Park. A Spectacular Ancient Ecosystem Revealed. Indiana University Press, Bloomington IN et al. 2005, ISBN 0-253-34595-2 , p. 553.
  40. ^ A b David P. Simpson: Cassell's Latin - English, English - Latin Dictionary. 5th edition. Cassell et al., London et al. 1979, p. 883.
  41. ^ John Harold Ostrom: A new species of hadrosaurian dinosaur from the Cretaceous of New Mexico. In: Journal of Paleontology. Vol. 35, No. 3, 1961, pp. 575-577.
  42. ↑ David B. Weishampel, James A. Jensen: Parasaurolophus (Reptilia; Hadrosauridae) from Utah. In: Journal of Paleontology. Vol. 53, No. 6, 1979, pp. 1422-1427.
  43. ↑ Andrew A. Farke, Derek J. Chok, Annisa Herrero, Brandon Scolieri, Sarah Werning: Ontogeny in the tube-crested dinosaur Parasaurolophus (Hadrosauridae) and heterochrony in hadrosaurids. In: PeerJ . , October 22, 2013, 1: e182 doi : 10.7717 / peerj.182 .
  44. ^ The "In a Land Before Our Time" DVD ( Memento from February 17, 2009 in the Internet Archive )
  45. ↑ Fantasia (1940). In: Movie Mistakes. Retrieved October 24, 2014 .
  46. ↑ Parasaurolophus. In: Park Pedia. Retrieved October 24, 2014 .
  47. ↑ Disney Dinosaur Interviews David Krentz. In: Dave Hone's Archosaur Musings. Retrieved October 24, 2014 .
This article was added to the list of excellent articles on August 25, 2009 in this version .