STYRACOSAURUS

'''Styracosaurus''' (meaning "spiked lizard" from Greek ''styrax/στυραξ'' 'spike at the butt-end of a spear-shaft' and ''saurus/σαυρος'' 'lizard')^[1] was a genus of herbivorous ceratopsian dinosaur from the Cretaceous Period (Campanian stage), about 76.5 to 75.0 million years ago. It had four to six long horns extending from its neck frill, a smaller horn on each of its cheeks, and a single horn protruding from its nose, which was around 60 centimeters (2 ft) long and 15 centimeters (6 in) wide. The function or functions of the horns and frills have been the subject of debate for many years.
''Styracosaurus'' was a large dinosaur, reaching lengths of 5.5 meters (18 ft) and weighing nearly 3 tons. It stood about 1.8 meters (6 ft) tall. ''Styracosaurus'' possessed four short legs and a bulky body. Its tail was rather short. It also had a beak and flat cheek teeth, indicating that its diet was herbivorous. Like other ceratopsians, this dinosaur may have been a herd animal, traveling in large groups, as suggested by bonebeds.
Named by Lawrence Lambe in 1913, ''Styracosaurus'' is a member of the Centrosaurinae. Three species, ''S. albertensis'', ''S. ovatus'', and ''S. parksi'' are currently assigned to ''Styracosaurus'', though the last species may be synonymous with ''S. albertensis''. Other species assigned to the genus have since been reassigned elsewhere.

Contents

Description

Classification

Origins

Discoveries and species

Paleobiology

Dentition and diet

Horns and frill

In popular culture

References

External links

Description

Individuals of the ''Styracosaurus'' genus were approximately 5.5 m (18 ft) long as adults and weighed around 2.7 tons.^[2] The skull was massive, with a large nostril, a tall straight nose horn estimated at 50 centimeters long (19.7 in) in the type specimen,^[3] and a parietosquasomal frill (a neck frill) crowned with four to six spikes, depending on the species. Each of the four longest frill spines was comparable in length to the nose horn, at 50 to 55 centimeters long (19.7 to 21.7 in). The lower parts of the frill had smaller hornlets and frill hooks similar to, but smaller than, those seen in ''Centrosaurus''. Like most ceratopsids, it had large fenestrae (skull openings) in its frill. The front of the mouth had a toothless beak. ''Styracosaurus'' had tiny, undeveloped brow horns above the eyes.
The bulky body of ''Styracosaurus'' resembled that of a rhinoceros. It had powerful shoulders which may have been useful in intraspecies combat. ''Styracosaurus'' had a relatively short tail. Each toe bore a hooflike ungual which was sheathed in horn.
Various limb positions have been proposed for ''Styracosaurus'' and ceratopsids in general, including forelegs which were held underneath the body, or, alternately, held in a sprawling position. The most recent work has put forward an intermediate crouched position as most likely. Forelimb stance and step cycle in ''Chasmosaurus irvinensis'' (Dinosauria:Neoceratopsia Thompson, Stefan Paleontologists Gregory Paul and Per Christiansen of the Zoological Museum of the University of Copenhagen in Denmark proposed that large ceratopsians such as ''Styracosaurus'' were able to run at speeds exceeding that of an elephant, based on possible ceratopsian trackways which did not exhibit signs of sprawling forelimbs.^[4]

Classification

''Styracosaurus'' is a member of the Centrosaurinae, a subfamily of large North American horned dinosaurs characterized by their "prominent nasal horns, subordinate brow horns, short squamosals in a short frill, a tall, deep face relative to the ceratopines, and a projection into the rear of the nasal fenestra."^[5] Other members of the clade include ''Centrosaurus'' (from which the group takes its name),^[6][7] ''Pachyrhinosaurus'',^[8] ''Avaceratops'', ''Einiosaurus'', ''Albertaceratops'',^[9] ''Achelousaurus'', ''Brachyceratops'',Dodson, P., Forster, C. A, and Sampson, S. D. (2004) ''Ceratopsidae''. In: Weishampel, D. B., Dodson, P., and Osmólska, H. (eds.), ''The Dinosauria'' (second edition). University of California Press:Berkeley, pp. 494–513. ISBN 0-520-24209-2. and ''Monoclonius'', although these last two are dubious. Because of the variation between species and even individual specimens of centrosaurines, there has been much debate over which genera and species are valid, particularly whether ''Centrosaurus'' and/or ''Monoclonius'' are valid genera, undiagnosable, or possibly members of the opposite sex. In 1996, Peter Dodson found enough variation between ''Centrosaurus'', ''Styracosaurus'', and ''Monoclonius'' to warrant separate genera, and that ''Styracosaurus'' resembled ''Centrosaurus'' more closely than either resembled ''Monoclonius''. Dodson also believed one species of ''Monoclonius'', ''M. nasicornis'', may actually have been a female ''Styracosaurus''.^[10] His assessments have been partially followed, with other researchers not accepting ''Monoclonius nasicornis'' as a female ''Styracosaurus'', or ''Monoclonius'' as a valid genus. Dinosaur Provincial Park: A Spectacular Ancient Ecosystem Revealed, , Michael J., Ryan, Indiana University Press, 2005, While sexual dimorphism has been proposed for an earlier ceratopsian ''Protoceratops'',^[11] there is no firm evidence for sexual dimorphism in any ceratopsids.Forster, C. A. (1990). The cranial morphology and systematics of ''Triceratops'', with a preliminary analysis of ceratopsian phylogeny. Ph.D. Dissertation. University of Pennsylvania, Philadelphia. 227 pp.^[12] Craniofacial ontogeny in centrosaurine dinosaurs (Ornithischia: Ceratopsidae): taphonomic and behavioral phylogenetic implications, , S. D., Sampson, Zoological Journal of the Linnean Society, 1997

Origins

The evolutionary origins of ''Styracosaurus'' were not understood for many years because fossil evidence for early ceratopsians was sparse. The discovery of ''Protoceratops'', in 1922, shed light on early ceratopsid relationships,^[13] but several decades passed before additional finds filled in more of the blanks. Fresh discoveries in the late 1990s and 2000s, including ''Zuniceratops'', the earliest known ceratopsian with brow horns, and ''Yinlong'', the first known Jurassic ceratopsian, indicate what dinosaurs related to the ancestors of ''Styracosaurus'' may have looked like. These new discoveries have been important in illustrating the origins of horned dinosaurs in general, and suggest that the group originated during the Jurassic in Asia, and the appearance of truly horned ceratopsians by the beginning of the late Cretaceous in North America.Dodson, P., Forster, C. A, and Sampson, S. D. (2004) ''Ceratopsidae''. In: Weishampel, D. B., Dodson, P., and Osmólska, H. (eds.), ''The Dinosauria'' (second edition). University of California Press:Berkeley, pp. 494–513. ISBN 0-520-24209-2.

Discoveries and species

The first fossil remains of ''Styracosaurus'' were collected in Alberta, Canada by C.M. Sternberg (from an area now known as the Dinosaur Provincial Park, in a formation now called the Dinosaur Park Formation) and named by Lawrence Lambe in 1913. This quarry was revisited in 1935 by a Royal Ontario Museum crew who found the missing lower jaws and most of the skeleton. These fossils indicate that ''S. albertensis'' was around 5.5 to 5.8 meters in length and stood about 1.65 meters high at the hips.
Barnum Brown and Erich Maren Schlaikjer, working for the American Museum of Natural History in New York, collected a nearly complete articulated skeleton with a partial skull in 1915. These fossils were also found in the Dinosaur Park Formation, near Steveville, Alberta. Brown and Schlaikjer compared the finds, and, though they allowed that both specimens were from the same general locality and geological formation, they considered the specimen sufficiently distinct from the holotype to warrant erecting a new species, and described the fossils as ''Styracosaurus parksi'', named in honor of William Parks.^[14] Among the differences between the specimens cited by Brown and Schlaikjer were a cheekbone quite different from that of ''S. albertensis'', and smaller tail vertebrae. ''S. parksi'' also had a more robust jaw, a shorter dentary, and the frill differed in shape from that of the type species. However, much of the skull consisted of plaster reconstruction, and the original 1937 paper did not illustrate the actual skull bones. Until a specimen in a better state of preservation is found, there are some lingering doubts amongst paleontologists about the validity of ''S. parksi''.
In the summer of 2006, Darren Tanke of the Royal Tyrrell Museum of Palaeontology in Drumheller, Alberta relocated the long lost ''S. parksi'' site. Pieces of the skull, evidently abandoned by the 1915 crew, were found in the quarry. These were collected and it is hoped more pieces will be found, perhaps enough to warrant a redescription of the skull and test whether ''S. albertensis'' and ''S. parksi'' are the same. The Tyrrell Museum has also collected several partial ''Styracosaurus'' skulls, and two confirmed bonebeds (bonebeds 42 and 156) in Dinosaur Provincial Park has also been explored. Bonebed 42 is known to contain numerous pieces of skulls such as horncores, jaws and frill pieces.
A third species, ''S. ovatus'', from the Two Medicine Formation of Montana, was described by Gilmore in 1930. The fossil material is limited, with the best being a portion of the parietal bone of the frill, but one unusual feature is that the pair of spikes closest to the midline converge towards the midline, rather than away from it as in ''S. albertensis''. There also may only have been two sets of spikes on each side of the frill, instead of three. The spikes are much shorter than in ''S. albertensis'', with the longest only 295 millimeters (11.6 in) long.^[15]
Several other species which were assigned to ''Styracosaurus'' have since been assigned to other genera. ''S. sphenocerus'', described by Edward Drinker Cope in 1890 as a species of ''Monoclonius'' and based on a nasal bone with a broken ''Styracosaurus''-like straight nose horn, was attributed to ''Styracosaurus'' in 1915.^[16] "S. makeli", mentioned informally by amateur paleontologists Stephen and Sylvia Czerkas in 1990 in a caption to an illustration, is an early name for ''Einiosaurus''. Dinosaurs: The Encyclopedia, , Donald F., Glut, McFarland & Co, 1997, "S. borealis" is an early informal name for ''S. parksi''. Dinosaurs: The Encyclopedia, , Donald F., Glut, McFarland & Co, 1997,

Paleobiology

''Styracosaurus'' and other horned dinosaurs are often depicted in popular culture as herding animals. Two bonebeds composed of ''Styracosaurus'' remains are known from the Dinosaur Park Formation of Alberta, about halfway up the formation. These bonebeds are associated with different types of river deposits. Dinosaur Provincial Park: A Spectacular Ancient Ecosystem Revealed, , David A., Eberth, Indiana University Press, 2005, The mass deaths may have been a result of otherwise non-herding animals congregating around a waterhole in a period of drought, with evidence suggesting the environment may have been seasonal and semiarid. Taphonomy of three dinosaur bone beds in the Upper Cretaceous Two Medicine Formation, northwestern Montana: Evidence for drought-related mortality, , R. R., Rogers, Palaios, 1990
''Styracosaurus'' is known from higher in the formation than the closely-related ''Centrosaurus'', suggesting that ''Styracosaurus'' displaced ''Centrosaurus'' as the environment changed over time. Dinosaur Provincial Park: A Spectacular Ancient Ecosystem Revealed, , Michael J., Ryan, Indiana University Press, 2005,

Dentition and diet

''Styracosaurus'' were herbivorous dinosaurs; they probably fed mostly on low growth because of the head's position. They may, however, have been able to knock down taller plants with their horns, beak, and bulk.^[17] The jaws were tipped with a deep, narrow beak, believed to have been better at grasping and plucking than biting.^[18]
Ceratopsid teeth, including those of ''Styracosaurus'', were arranged in groups called batteries. Older teeth on top were continually replaced by the teeth underneath them; this occurred throughout the life of the animal. Unlike hadrosaurids, which also had dental batteries, ceratopsid teeth sliced but did not grind. Some scientists have suggested ceratopsids like ''Styracosaurus'' ate palms and cycads,^[19] while others have suggested ferns.^[20] Dodson has proposed that Late Cretaceous ceratopsians may have knocked down angiosperm trees and then sheared off leaves and twigs.^[21]

Horns and frill

The large nasal horns and frills of ''Styracosaurus'' are among the most distinctive facial adornments of all dinosaurs. Their function has been the subject of debate ever since the first horned dinosaurs were discovered.
Early in the 20th century, paleontologist R. S. Lull put forth the hypothesis that the frills of ceratopsian dinosaurs acted as anchor points for their jaw muscles. The cranial musculature and the origin of the frill in the ceratopsian dinosaurs, , R.S., Lull, American Journal of Science, 1908 He later noted that for ''Styracosaurus'', the spikes would have given it a formidable appearance.^[22] In 1996, Dodson supported the idea of muscle attachments in part and created detailed diagrams of possible muscle attachments in the frills of ''Styracosaurus'' and ''Chasmosaurus'', but did not subscribe to the idea that they completely filled in the fenestrae.^[23] C.A. Forster, however, found no evidence of large muscle attachments on the frill bones.^[24]
It was long believed ceratopsians like ''Styracosaurus'' used their frills and horns in defence against the large predatory dinosaurs of the time. Although pitting, holes, lesions, and other damage on ceratopsid skulls are often attributed to horn damage in combat, a 2006 study found no evidence for horn thrust injuries causing these forms of damage (for example, there is no evidence of infection or healing). Instead, non-pathological bone resorption, or unknown bone diseases, are suggested as causes.^[25]
The large frill on ''Styracosaurus'' and related genera also may have helped to increase body area to regulate body temperature,^[26] like the ears of the modern elephant. A similar theory has been proposed regarding the plates of ''Stegosaurus'',^[27] although this use alone would not account for the bizarre and extravagant variation seen in different members of the Ceratopsidae. This observation is highly suggestive of what is now believed to be the primary function, display.
The theory of frill use in sexual display was first proposed in 1961 by Davitashvili. This theory has gained increasing acceptance. The Theory of sexual selection, Davitashvili L, , , Izdatel'stvo Akademii Nauk SSSR, 1961, Evidence that visual display was important, either in courtship or in other social behavior, can be seen in the fact that horned dinosaurs differ markedly in their adornments, making each species highly distinctive. Also, modern living creatures with such displays of horns and adornments use them in similar behavior.^[28]

In popular culture

Because of the distinctive frill and horns of ''Styracosaurus'', the genus is easily recognizable. The spines, hooks, and horns attached to the head of this dinosaur sparked the imagination of filmmakers during the earliest days of motion pictures, and this has led to its appearance in films ever since. Among the most notable motion pictures in which styracosaurs have appeared are: ''The Son of Kong'' (1933), where a ''Styracosaurus'' battles the movie's heroes;^[29] ''The Valley of Gwangi'' (1969), where ''Styracosaurus'' is pitted against a carnivorous dinosaur;^[30] and Disney's CGI film ''Dinosaur'' (2000), where an anthropomorphic ''Styracosaurus'' named Eema has a pet ''Ankylosaurus''.^[31] The genus also appeared in the novel of ''Jurassic Park'', in the list of dinosaurs present in the park, but was not seen in the film adaptation.
On the small screen, ''Styracosaurus'' has appeared in many cartoons and anime, including ''Dinosaucers''^[32] and ''Zoids''.^[33] ''Styracosaurus'' has also been featured in various video games, including the popular ''Jurassic Park'', ''Turok'', and '' game franchises.

References

1. Greek-English Lexicon, Abridged Edition, Liddell & Scott, , , Oxford University Press, Oxford, UK, 1980, ISBN 0-19-910207-4
2. Lambert, D. (1993). ''The Ultimate Dinosaur Book.'' Dorling Kindersley: New York, 152–167. ISBN 1-56458-304-X.
3. The Horned Dinosaurs: A Natural History, , P., Dodson, Princeton University Press, ,
4.
5. Centrosaurinae
6. Dinosaur Systematics: Perspectives and Approaches, , P., Dodson, Cambridge University Press, 1990,
7. New centrosaurine ceratopsids from the late Campanian of Alberta and Montana and a review of contemporaneous and regional patterns of centrosaurine evolution, , M.J., Ryan, Journal of Vertebrate Paleontology,
8. A new centrosaurine ceratopsid from the Oldman Formation of Alberta and its implications for centrosaurine taxonomy and systematics, , M.J., Ryan, Canadian Journal of Earth Sciences,
9. A new basal centrosaurine ceratopsid from the Oldman Formation, southeastern Alberta, , M.J., Ryan, Journal of Paleontology,
10. Dodson, P. (1996). ''The Horned Dinosaurs: A Natural History''. Princeton University Press: Princeton, New Jersey, p. 197–199. ISBN 0-691-02882-6.
11. Quantitative aspects of relative growth and sexual dimorphism in ''Protoceratops'', , P., Dodson, Journal of Paleontology,

12. A gigantic skull and skeleton of the horned dinosaur ''Pentaceratops sternbergi'' from New Mexico, , T. M., Lehman, Journal of Paleontology, 1998
13. Dodson, P. (1996). ''The Horned Dinosaurs: A Natural History''. Princeton University Press: Princeton, New Jersey, p. 244. ISBN 0-691-02882-6.
14. The skeleton of ''Styracosaurus'' with the description of a new species, , Barnum, Brown, American Museum novitates,
15. On dinosaurian reptiles from the Two Medicine Formation of Montana, , Charles W., Gilmore, Proceedings of the United States National Museum, 1930
16. On ''Eoceratops canadensis'', gen. nov., with remarks on other genera of Cretaceous horned dinosaurs, , L. M., Lambe, Canada Geological Survey Bulletin, Geological Series, 1915
17. Tait J., and Brown, B. (1928). How the Ceratopsia carried and used their head. ''Transactions of the Royal Society of Canada.'' '22':13–23.
18. Functional morphology and evolution of the ceratopsian dinosaurs, Ostrom, J. H., , , Evolution,
19. Weishampel, D. B. (1984). Evolution of jaw mechanisms in ornithopod dinosaurs. ''Advances in Anatomy, Embryology, and Cell Biology'' '87':1–110.
20. Coe, M. J., Dilcher, D. L., Farlow, J. O., Jarzen, D. M., and Russell, D. A. (1987). Dinosaurs and land plants. In: Friis, E. M., Chaloner, W. G., and Crane, P. R. (eds.) ''The Origins of Angiosperms and their Biological Consequences'' Cambridge University Press, pp. 225–258. ISBN 0-521-32357-6.
21. Dodson, P. (1996). ''The Horned Dinosaurs: A Natural History''. Princeton University Press: Princeton, New Jersey, p. 266. ISBN 0-691-02882-6.
22. A revision of the Ceratopsia or horned dinosaurs, , R.S., Lull, Memoirs of the Peabody Museum of Natural History, 1933
23. Dodson, P. (1996). ''The Horned Dinosaurs: A Natural History''. Princeton University Press: Princeton, New Jersey, p. 269. ISBN 0-691-02882-6.
24. Forster, C. A. (1990). The cranial morphology and systematics of ''Triceratops'', with a preliminary analysis of ceratopsian phylogeny. Ph.D. Dissertation. University of Pennsylvania, Philadelphia. 227 pp. OCLC 61500040
25. Tanke, D. H, and Farke, A. A. (2006). Bone resorption, bone lesions, and extracranial fenestrae in ceratopsid dinosaurs: a preliminary assessment. in: Carpenter, K. (ed.). ''Horns and Beaks: Ceratopsian and Ornithopod Dinosaurs'' Indiana University Press: Bloomington. pp. 319–347. ISBN 0-253-34817-X.
26. Elaborate CNS cooling structures in large dinosaurs, Wheeler, P.E., , , Nature,
27. Plates of the dinosaur ''Stegosaurus'': Forced convection heat loss fins?, Farlow, J. O., Thompson, C. V., and Rosner, D. E., , , Science,
28. The behavioral significance of frill and horn morphology in ceratopsian dinosaurs, Farlow, J. O., and Dodson, P., , , Evolution,
29. DVD Savant Review: ''The Son of Kong''
30. The Styracosaurus 1969
31. Dinosaur
32. Dinosaucers Cast and Crew
33. Red Horn

External links

★ ''Styracosaurus'', from the Dinosaur Encyclopaedia