Dilophosaurus
Dilophosaurus | |
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Reconstructed cast of the holotype specimen (UCMP 37302) in position of burial, Royal Ontario Museum
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Dinosauria |
Clade: | Saurischia |
Clade: | Theropoda |
Clade: | Neotheropoda |
Genus: | †Dilophosaurus Welles, 1970 |
Species: | †D. wetherilli
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Binomial name | |
†Dilophosaurus wetherilli (Welles, 1954)
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Synonyms | |
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Dilophosaurus (
At about 7 m (23 ft) in length, with a weight of about 400 kg (880 lb), Dilophosaurus was one of the earliest large predatory dinosaurs and the largest known land-animal in North America at the time. It was slender and lightly built, and the skull was proportionally large, but delicate. The snout was narrow, and the upper jaw had a gap or kink below the nostril. It had a pair of longitudinal, arched crests on its skull; their complete shape is unknown, but they were probably enlarged by
Dilophosaurus has been considered a member of the family
History of discovery
In the summer of 1942, the paleontologist
The nearly complete first specimen was cleaned and mounted at the UCMP under supervision of the paleontologist
Welles returned to Tuba City in 1964 to determine the age of the Kayenta Formation (it had been suggested to be Late Triassic in age, whereas Welles thought it was Early to Middle Jurassic), and discovered another skeleton about 400 m (1⁄4 mi) south of where the 1942 specimens had been found. The nearly complete specimen (catalogued as UCMP 77270) was collected with the help of William J. Breed of the Museum of Northern Arizona and others. During preparation of this specimen, it became clear that it was a larger individual of M. wetherilli, and that it would have had two crests on the top of its skull. Being a thin plate of bone, one crest was originally thought to be part of the missing left side of the skull, which had been pulled out of its position by a scavenger. When it became apparent that it was a crest, it was also realized that a corresponding crest would have been on the left side, since the right crest was right of the midline, and was concave along its middle length. This discovery led to re-examination of the holotype specimen, which was found to have bases of two thin, upwards-extended bones, which were crushed together. These also represented crests, but they had formerly been assumed to be part of a misplaced cheek bone. The two 1942 specimens were also found to be juveniles, while the 1964 specimen was an adult, about one-third larger than the others.[2][7][8] Welles later recalled that he thought the crests were as unexpected as finding "wings on a worm".[9]
New genus and subsequent discoveries
Welles and an assistant subsequently corrected the wall mount of the holotype specimen based on the new skeleton, by restoring the crests, redoing the pelvis, making the neck ribs longer, and placing them closer together. After studying the skeletons of North American and European theropods, Welles realized that the dinosaur did not belong to Megalosaurus, and needed a new genus name. At that time, no other theropods with large longitudinal crests on their heads were known, and the dinosaur had therefore gained the interest of paleontologists. A mold of the holotype specimen was made, and fiberglass casts of it were distributed to various exhibits; to make labeling these casts easier, Welles decided to name the new genus in a brief note, rather than wait until the publication of a detailed description. In 1970, Welles coined the new genus name Dilophosaurus, from the Greek words di (δι) meaning "two", lophos (λόφος) meaning "crest", and sauros (σαυρος) meaning "lizard": "two-crested lizard". Welles published a detailed
In 2001, the paleontologist Robert J. Gay identified the remains of at least three new Dilophosaurus specimens (this number is based on the presence of three pubic bone fragments and two differentially sized femora) in the collections of the Museum of Northern Arizona. The specimens were found in 1978 in the Rock Head Quadrangle, 190 km (120 mi) away from where the original specimens were found, and had been labeled as a "large theropod". Though most of the material is damaged, it is significant in including elements not preserved in the earlier specimens, including part of the pelvis and several ribs. Some elements in the collection belonged to an infant specimen (MNA P1.3181), the youngest known example of this genus, and one of the earliest known infant theropods from North America, only preceded by some Coelophysis specimens. The juvenile specimen includes a partial humerus, a partial fibula, and a tooth fragment.[12] In 2005, paleontologist Ronald S. Tykoski assigned a specimen (TMM 43646-140) from Gold Spring, Arizona, to Dilophosaurus, but in 2012, paleontologist Matthew T. Carrano and colleagues found it to differ in some details.[13][14]
In 2020, the paleontologists Adam D. Marsh and Timothy B. Rowe comprehensively redescribed Dilophosaurus based on the by then known specimens, including specimen UCMP 77270 which had remained undescribed since 1964. They also removed some previously assigned specimens, finding them too fragmentary to identify, and relocated the type quarry with the help of a relative of Jesse Williams.[6][15] In an interview, Marsh called Dilophosaurus the "best worst-known dinosaur", since the animal was poorly understood despite having been discovered 80 years earlier. A major problem was that previous studies of the specimens did not make clear which parts were original fossils and which were reconstructed in plaster, yet subsequent researchers only had Welles' 1984 monograph to rely on for subsequent studies, muddling understanding of the dinosaur's anatomy. Marsh spent seven years studying the specimens to clarify the issues surrounding the dinosaur, including two specimens found two decades earlier by Rowe, his Ph.D. advisor.[16]
Formerly assigned species
In 1984, Welles suggested that the 1964 specimen (UCMP 77270) did not belong to Dilophosaurus, but to a new genus, based on differences in the skull, vertebrae, and femora. He maintained that both genera bore crests, but that the exact shape of these was unknown in Dilophosaurus.[2] Welles died in 1997, before he could name this supposed new dinosaur, and the idea that the two were separate genera has generally been ignored or forgotten since.[5] In 1999, amateur paleontologist Stephan Pickering privately published the new name Dilophosaurus "breedorum" based on the 1964 specimen, named in honor of Breed, who had assisted in collecting it. This name is considered a nomen nudum, an invalidly published name, and Gay pointed out in 2005 that no significant differences exist between D. "breedorum" and other D. wetherilli specimens.[17][18] In 2012, Carrano and colleagues found differences between the 1964 specimen and the holotype specimen, but attributed them to variation between individuals rather than species.[13] Paleontologists Christophe Hendrickx and Octávio Mateus suggested in 2014 that the known specimens might represent two species of Dilophosaurus based on different skull features and stratigraphic separation, pending thorough description of assigned specimens.[19] Marsh and Rowe concluded in 2020 that there was only one taxon among known Dilophosaurus specimens, and that differences between them were due to their different degree of maturity and preservation. They did not find considerable stratigraphic separation between the specimens either.[6]
A nearly complete theropod skeleton (KMV 8701) was discovered in the
Description
Dilophosaurus was one of the earliest large predatory
Skull
The skull of Dilophosaurus was large in proportion to the overall skeleton, yet delicate. The snout was narrow in front view, becoming narrower towards the rounded top. The
The outer surface of the premaxilla was covered in
Dilophosaurus bore a pair of high, thin, and arched (or plate-shaped) crests longitudinally on the skull roof. The crests (termed the nasolacrimal crests) began as low ridges on the premaxillae and were mainly formed by the upwards expanded
The orbit was oval, and narrow towards the bottom. The
Dilophosaurus had four teeth in each premaxilla, 12 in each maxilla, and 17 in each dentary. The teeth were generally long, thin, and recurved, with relatively small bases. They were compressed sideways, oval in cross-section at the base, lenticular (lens-shaped) above, and slightly concave on their outer and inner sides. The largest tooth of the maxilla was either in or near the fourth alveolus, and the height of the tooth crowns decreased hindwards. The first tooth of the maxilla pointed slightly forwards from its alveolus because the lower border of the premaxilla process (which projected backward towards the maxilla) was upturned. The teeth of the dentary were much smaller than those of the maxilla. The third or fourth tooth in the dentary of Dilophosaurus and some coelophysoids was the largest there, and seems to have fit into the subnarial gap of the upper jaw. Most of the teeth had serrations on the front and back edges, which were offset by vertical grooves, and were smaller at the front. About 31 to 41 serrations were on the front edges, and 29 to 33 were on the back. At least the second and third teeth of the premaxilla had serrations, but the fourth tooth did not. The teeth were covered in a thin layer of
Postcranial skeleton
Dilophosaurus had 10 cervical (neck), 14 dorsal (back), and 45 caudal (tail) vertebrae, and air sacs grew into the vertebrae. It had a long neck, which was probably flexed nearly 90° by the skull and by the shoulder, holding the skull in a horizontal posture. The cervical vertebrae were unusually light; their centra (the "bodies" of the vertebrae) were hollowed out by pleurocoels (depressions on the sides) and centrocoels (cavities on the inside). The arches of the cervical vertebrae also had pneumatic fossae (or chonoses), conical recesses so large that the bones separating them were sometimes paper-thin. The centra were plano-concave, flat to weakly convex at the front and deeply cupped (or concave) at the back, similar to Ceratosaurus. This indicates that the neck was flexible, though it had long, overlapping cervical ribs, which were fused to the centra. The cervical ribs were slender and may have bent easily.[2][31][6][15]
The
The
The
Classification
Welles thought Dilophosaurus a
In 1988, paleontologist
Lamanna and colleagues pointed out in 1998 that since Dilophosaurus was discovered to have had crests on its skull, other similarly crested theropods have been discovered (including Sinosaurus), and that this feature is, therefore, not unique to the genus, and of limited use for determining interrelationships within their group.
In 2007, paleontologist Nathan D. Smith and colleagues found the crested theropod
Paleontologist Christophe Hendrickx and colleagues defined the Dilophosauridae to include Dilophosaurus and Dracovenator in 2015, and noted that while general uncertainty exists about the placement of this group, it appears to be slightly more derived than the Coelophysoidea, and the sister group to the
Neotheropoda |
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In 2019, paleontologists Marion Zahner and Winand Brinkmann found the members of the Dilophosauridae to be successive basal sister taxa of the Averostra rather than a
Ichnology
Various
The paleontologist Gerard Gierliński examined tridactyl footprints from the
The paleontologist Robert E. Weems proposed in 2003 that Eubrontes tracks were not produced by a theropod, but by a
In 2006, Weems defended his 2003 assessment of Eubrontes, and proposed an animal like Dilophosaurus as the possible trackmaker of numerous Kayentapus trackways of the Culpeper Quarry in Virginia. Weems suggested rounded impressions associated with some of these trackways to represent hand impressions lacking digit traces, which he interpreted as a trace of quadrupedal movement.
Paleobiology
Feeding and diet
Welles found that Dilophosaurus did not have a powerful bite, due to weakness caused by the subnarial gap. He thought that it used its front premaxillary teeth for plucking and tearing rather than biting, and the maxillary teeth further back for piercing and slicing. He thought that it was probably a scavenger rather than a predator, and that if it did kill large animals, it would have done so with its hands and feet rather than its jaws. Welles did not find evidence of
A 2005
Milner and paleontologist
In 2018, Marsh and Rowe reported that the holotype specimen of the sauropodomorph Sarahsaurus bore possible tooth marks scattered across the skeleton that may have been left by Dilophosaurus (Syntarsus was too small to have produced them) scavenging the specimen after it died (the positions of the bones may also have been disturbed by scavenging). An example of such marks can be seen on the left scapula, which has an oval depression on the surface of its upper side, and a large hole on the lower front end of the right tibia. The quarry where the holotype and paratype specimens of Sarahsaurus were excavated also contained a partial immature Dilophosaurus specimen.[54] Marsh and Rowe suggested in 2020 that many of the features that distinguished Dilophosaurus from earlier theropods were associated with increased body size and macropredation (preying on large animals). While Marsh and Rowe agreed that Dilophosaurus could have fed on fish and small prey in the fluvial system in its environment, they pointed out that the articulation between the premaxilla and maxilla of the upper jaw was immobile and much more robust than previously thought, and that large-bodied prey could have been grasped and manipulated with the forelimbs during predation and scavenging. They considered the large bite marks on Sarahsaurus specimens alongside shed teeth and the presence of a Dilophosaurus specimen within the same quarry as support for this idea.[6]
In a 2021 article, paleontologist Matthew A. Brown and Rowe stated that these remains showed that Dilophosaurus had jaws strong enough to puncture bone. The fleshy air sacs from its respiratory system that grew into the vertebrae both strengthened and lightened the skeleton, and allowed unidirectional airflow through its lungs, similar to birds and crocodiles, and thereby more oxygen than a bidirectional respiratory system of mammals (wherein the air flows in and out of the lungs). Unidirectional breathing indicates relatively high metabolic rates and therefore high levels of activity, indicating that Dilophosaurus was likely a fast, agile hunter. Brown and Rowe considered Dilophosaurus to have been an apex predator in its ecosystem, and not a scavenger.[15]
Motion
Welles envisioned Dilophosaurus as an active, clearly bipedal animal, similar to an enlarged ostrich. He found the forelimbs to have been powerful weapons, strong and flexible, and not used for locomotion. He noted that the hands were capable of grasping and slashing, of meeting each other, and reaching two-thirds up the neck. He proposed that in a sitting posture, the animal would rest on the large "foot" of its ischium, as well as its tail and feet.[2] In 1990, paleontologists Stephen and Sylvia Czerkas suggested that the weak pelvis of Dilophosaurus could have been an adaptation for an aquatic lifestyle, where the water would help support its weight, and that it could have been an efficient swimmer. They found it doubtful that it would have been restricted to a watery environment, though, due to the strength and proportions of its hind limbs, which would have made it fleet-footed and agile during bipedal locomotion.[55] Paul depicted Dilophosaurus bouncing on its tail while lashing out at an enemy, similar to a kangaroo.[56]
In 2005, paleontologists Phil Senter and James H. Robins examined the range of motion in the forelimbs of Dilophosaurus and other theropods. They found that Dilophosaurus would have been able to draw its humerus backward until it was almost parallel with the scapula, but could not move it forwards to a more than vertical orientation. The elbow could approach full extension and flexion at a right angle, but not achieve it completely. The fingers do not appear to have been voluntarily hyperextensible (able to extend backwards, beyond their normal range), but they may have been passively hyperextensible, to resist dislocation during violent movements by captured prey.[57] A 2015 article by Senter and Robins gave recommendations for how to reconstruct the fore limb posture in bipedal dinosaurs, based on examination of various taxa, including Dilophosaurus. The scapulae were held very horizontally, the resting orientation of the elbow would have been close to a right angle, and the orientation of the hand would not have deviated much from that of the lower arm.[58]
In 2018, Senter and Corwin Sullivan examined the range of motion in the fore limb joints of Dilophosaurus by manipulating the bones, to test hypothesized functions of the fore limbs. They also took into account that experiments with
Senter and Sullivan concluded that Dilophosaurus was able to grip and hold objects between two hands, to grip and hold small objects in one hand, to seize objects close beneath the chest, to bring an object to the mouth, to perform a display by swinging the arms in an arc along the sides of the ribcage, to scratch the chest, belly, or the half of the other forelimb farthest from the body, to seize prey beneath the chest or the base of the neck, and to clutch objects to the chest. Dilophosaurus was unable to perform scratch-digging, hook-pulling, to hold objects between two fingertips of one hand, to maintain balance by extending the arms outwards to the sides, or to probe small crevices like the modern
The Dilophosauripus footprints reported by Welles in 1971 were all on the same level, and were described as a "chicken yard hodge-podge" of footprints, with few forming a trackway. The footprints had been imprinted in mud, which allowed the feet to sink down 5–10 cm (2–4 in). The prints were sloppy, and the varying breadth of the toe prints indicates that mud had clung to the feet. The impressions varied according to differences in the substrate and the manner in which they were made; sometimes, the foot was planted directly, but often a backward or forward slip occurred as the foot came down. The positions and angles of the toes also varied considerably, which indicate they must have been quite flexible. The Dilophosauripus footprints had an offset second toe with a thick base, and very long, straight claws that were in line with the axes of the toe pads. One of the footprints was missing the claw of the second toe, perhaps due to injury.
Milner and colleagues examined the possible Dilophosaurus trackway SGDS 18.T1 in 2009, which consists of typical footprints with tail drags and a more unusual resting trace, deposited in
Crouching is a rarely captured behavior of theropods, and SGDS 18.T1 is the only such track with unambiguous impressions of theropod hands, which provides valuable information about how they used their forelimbs. The crouching posture was found to be very similar to that of modern birds, and shows that early theropods held the palms of their hands facing medially, towards each other. As such a posture therefore evolved early in the lineage, it may have characterized all theropods. Theropods are often depicted with their palms facing downwards, but studies of their functional anatomy have shown that they, like birds, were unable to pronate or supinate their arms. The track showed that the legs were held symmetrically with the body weight distributed between the feet and the metatarsals, which is also a feature seen in birds such as
Crest function
Welles conceded that suggestions as to the function of the crests of Dilophosaurus were conjectural, but thought that, though the crests had no grooves to indicate vascularization, they could have been used for
In 2011 the paleontologists
In 2013, paleontologists David E. Hone and Darren Naish criticized the "species recognition hypothesis", and argued that no extant animals use such structures primarily for species recognition, and that Padian and Horner had ignored the possibility of mutual sexual selection (where both sexes are ornamented).[63] Marsh and Rowe agreed in 2020 that the crests of Dilophosaurus likely had a role in species identification or intersexual/intrasexual selection, as in some modern birds.[6] It is unknown if the air sacs in the crests supported such functions.[15]
Development
Welles originally interpreted the smaller Dilophosaurus specimens as juveniles, and the larger specimen as an adult, later interpreting them as different species.[2][7] Paul suggested that the differences between the specimens was perhaps due to sexual dimorphism, as was seemingly also apparent in Coelophysis, which had "robust" and "gracile" forms of the same size, that might otherwise have been regarded as separate species. Following this scheme, the smaller Dilophosaurus specimen would represent a "gracile" example.[24]
In 2005 Tykoski found that most Dilophosaurus specimens known were juvenile individuals, with only the largest an adult, based on the level of co-ossification of the bones.[14] In 2005 Gay found no evidence of the sexual dimorphism suggested by Paul (but supposedly present in Coelophysis), and attributed the variation seen between Dilophosaurus specimens to individual variation and ontogeny (changes during growth). There was no dimorphism in the skeletons, but he did not rule out that there could have been in the crests; more data was needed to determine this.[17] Based on the tiny nasal crests on a juvenile specimen, Yates had tentatively assigned to the related genus Dracovenator, he suggested that these would have grown larger as the animal became adult.[36]
The paleontologist J.S. Tkach reported a
Welles found that the replacement teeth of Dilophosaurus and other theropods originated deep inside the bone, decreasing in size the farther they were from the alveolar border. There were usually two or three replacement teeth in the alveoli, with the youngest being a small, hollow
Paleopathology
Welles noted various
In 2016 Senter and Sara L. Juengst examined the paleopathologies of the holotype specimen and found that it bore the greatest and most varied number of such maladies on the pectoral girdle and forelimb of any theropod dinosaur so far described, some of which are not known from any other dinosaur. Only six other theropods are known with more than one paleopathology on the pectoral girdle and forelimbs. The holotype specimen had eight afflicted bones, whereas no other theropod specimen is known with more than four. On its left side, it had a fractured scapula and radius, and fibriscesses (like abscesses) in the ulna and the outer
The number of traumatic events that led to these features is not certain, and it is possible that they were all caused by a single encounter, for example by crashing into a tree or rock during a fight with another animal, which may have caused puncture wounds with its claws. Since all the injuries had healed, it is certain that the Dilophosaurus survived for a long time after these events, for months, perhaps years. The use of the forelimbs for prey capture must have been compromised during the healing process. The dinosaur may therefore have endured a long period of fasting or subsisted on prey that was small enough for it to dispatch with the mouth and feet, or with one forelimb.[67]
According to Senter and Juengst, the high degree of pain the dinosaur might have experienced in multiple locations for long durations also shows that it was a hardy animal. They noted that paleopathologies in dinosaurs are underreported, and that even though Welles had thoroughly described the holotype, he had mentioned only one of the pathologies found by them. They suggested that such features may sometimes be omitted because descriptions of species are concerned with their characteristics rather than abnormalities, or because such features are difficult to recognize.[67] Senter and Sullivan found that the pathologies significantly altered the range of motion in the right shoulder and right third finger of the holotype, and that estimates for range of motion may therefore not match those made for a healthy forelimb.[59]
Paleoenvironment
Dilophosaurus is known from the Kayenta Formation, which dates to the
The Kayenta Formation has yielded a small but growing assemblage of organisms. Most fossils are from the siltstone facies.
Taphonomy
Welles outlined the
Cultural significance
According to
The cliffs in Arizona that contained the bones of Dilophosaurus also have
Dilophosaurus was proposed as the state dinosaur of Arizona by a nine-year-old boy in 1998, but lawmakers suggested Sonorasaurus instead, arguing that Dilophosaurus was not unique to Arizona. A compromise was suggested that would recognize both dinosaurs, but the bill died when it was revealed that the Dilophosaurus fossils had been taken without permission from the Navajo Reservation, and because they did not reside in Arizona anymore (an 11-year-old boy again suggested Sonorasaurus as Arizona's state dinosaur in 2018). Navajo Nation officials subsequently discussed how to get the fossils returned.[85][86] According to Mayor, one Navajo stated that they do not ask to get the fossils back anymore, but wondered why casts had not been made so the bones could be left, as it would be better to keep them in the ground, and a museum built so people could come to see them there.[82] Further field work related to Dilophosaurus in the Navajo Nation was conducted with permission from the Navajo Nation Minerals Department.[15]
Jurassic Park
Dilophosaurus was featured in the 1990 novel
The geologist J. Bret Bennington noted in 1996 that though Dilophosaurus probably did not have a frill and could not spit venom like in the movie, its bite could have been venomous, as has been claimed for the Komodo dragon. He found that adding venom to the dinosaur was no less allowable than giving a color to its skin, which is also unknown. If the dinosaur had a frill, there would have been evidence for this in the bones, in the shape of a rigid structure to hold up the frill, or markings at the places where the muscles used to move it were attached. He also added that if it did have a frill, it would not have used it to intimidate its meal, but rather a competitor (he speculated it may have responded to a character in the movie pulling a hood over his head).[90] In a 1997 review of a book about the science of Jurassic Park, the paleontologist Peter Dodson likewise pointed out the wrong scale of the film's Dilophosaurus, as well as the improbability of its venom and frill.[91] Bakker pointed out in 2014 that the movie's Dilophosaurus lacked the prominent notch in the upper jaw, and concluded that the movie-makers had done a good job at creating a frightening chimaera of different animals, but warned it could not be used to teach about the real animal.[92] Brown and Marsh stated that while these traits were fictitious, they were made believable by being based on the biology of real animals.[15] Welles himself was "thrilled" to see Dilophosaurus in Jurassic Park: he noted the inaccuracies, but found them minor points, enjoyed the movie, and was happy to find the dinosaur "an internationally known actor".[93]
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- .
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- JSTOR 4523755.
- ISBN 978-0-253-33907-2.
- ISBN 978-0-253-33907-2.
- ^ PMID 26909701.
- .
- ISSN 1731-3708.)
{{cite journal}}
: CS1 maint: DOI inactive as of January 2024 (link - ^ a b Harshbarger, J. W.; Repenning, C. A.; Irwin, J. H. (1957). "Stratigraphy of the uppermost Triassic and the Jurassic rocks of the Navajo country". New Mexico Geological Society. 291: 98–114.
- ^ a b c Lucas, S.G.; Heckert, A. B.; Tanner, L.H. (2005). "Arizona's Jurassic fossil vertebrates and the age of the Glen Canyon Group". New Mexico Museum of Natural History Bulletins. 29: 95–104.
- ^ a b c Luttrell, P.R.; Morales, M. (1993). "Bridging the gap across Moenkopi Wash: a lithostratigraphic correlation". Museum of Northern Arizona Bulletin. 59: 111–127.
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- ^ Rigby, J.K.; Hamblin, W.K.; Matheny, R.; Welsh, S.L. (1971). "Guidebook to the Colorado river: Part 3, Moab to Hite, Utah through Canyonlands National Park" (PDF). Brigham Young University Research Studies, Geology Series. 18 (2): 7. Archived from the original (PDF) on November 25, 2020. Retrieved February 15, 2018.
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- ^ Curtis, K.; Padian, K. (1999). "An Early Jurassic microvertebrate fauna from the Kayenta Formation of northeastern Arizona: microfaunal change across the Triassic-Jurassic boundary". PaleoBios. 19 (2): 19–37.
- ^ S2CID 35607107.
- ISBN 978-0-557-46616-0.
- PMID 20926438.
- ISBN 978-1-882054-10-7.
- S2CID 129785393.
- ^ JSTOR j.ctt4cgcs9.10.
- ^ Stone, M. (2017). "Connecticut welcomes its new state dinosaur". CTBoom.com. Archived from the original on September 25, 2017. Retrieved February 13, 2018.
- ^ Rogers, O. (2016). "Discovered dinosaur tracks re-route highway and lead to state park". Connecticut History. Retrieved January 3, 2018.
- ^ Moeser, C. (April 26, 1998). "Arizona dinosaur debate becomes real Godzilla". The Arizona Republic. Deseret News. Retrieved May 12, 2020.
- ^ Gebers, S. (February 19, 2018). "Arizona has no official state dinosaur, so an 11 year-old proposed one – the Sonorasaurus". The Republic. Retrieved February 20, 2018 – via AZ Central.
- ISBN 978-0-394-58816-2.
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- ^ Bennington, J.B. (1996). "Errors in the movie Jurassic Park". American Paleontologist. 4 (2): 4–7. Archived from the original on October 2, 2018. Retrieved December 28, 2017.
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- ^ Bakker, R.T. (2014). "A tale of two compys: What Jurassic Park got right – and wrong – about dino anatomy". blog.hmns.org. The Houston Museum of Natural Science. Retrieved August 18, 2020.
- ^ Welles, S.P.; Guralnick, R.P. (1994). "Dilophosaurus, the actor". ucmp.berkeley.edu. University of California, Berkeley. Archived from the original on January 4, 2018. Retrieved February 13, 2018.
External links
- "Dilophosaurus! A Narrated Exhibition". With Samuel P. Welles.
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: CS1 maint: others (link)