Styracosaurus
| Styracosaurus Temporal range: Late Cretaceous
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| Model Styracosaurus, Bałtów Jurassic Park, Poland. | |
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| Genus: | Styracosaurus Lambe, 1913
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S. albertensis | |
Styracosaurus (meaning "spiked lizard" from Greek styrax/στυραξ 'spike at the butt-end of a spear-shaft' and saurus/σαυρος 'lizard') was a genus of herbivorous ceratopsian dinosaur from the Cretaceous Period (Campanian stage), about 80 million years ago. It had six long horns extending from its neck frill, a smaller horn above each of its eyes and a single horn protruding from its nose, at 60 centimeters (2 feet) long and 15 centimeters (6 inches) wide. The exact function of the horns and frills have been the subject of debate for many years.
Styracosaurus was a large dinosaur, reaching lengths of 5 meters (18 feet) and weighing as much as 3 tons. It stood about 1.8 meters (6 feet) 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 was most likely a herd animal, traveling in large groups and caring for its young after they hatched.
Description
Individuals of the Styracosaurus genus were approximately 5.5 meters (18 ft) long and weighed around 2.7 tons.[1] The skull was massive, with a large naris, a big nose horn, and a parietosquasomal frill crowned with four to six (depending on the species) spikes. Each of the four longest frill spines was as long as a human arm. The lower parts of the frill had small frill hooks smiliar to, but smaller than, those seen in Centrosaurus. Unlike Triceratops, Styracosaurus had large fenestrae (skull openings) in its frill. The front of the mouth had a toothless beak. Above the eyes, Styracosaurus had tiny, undeveloped brow horns.
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.[1]
Posture
Various limb positions have been proposed for Styracosaurus. Paleontologists Gregory Paul and Per Christiansen of the Zoological Museum of Denmark proposed large that ceratopsians such as Styracosaurus were able to run at speeds exceding that of an elephant, based on possible ceratopsian trackways which did not exhibit signs of sprawling forelimbs.[2]
Classification
Styracosaurus is a member of the Centrosaurinae, a family 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. Other members of the clade include Centrosaurus (from which the group takes its name), Monoclonius, Brachyceratops, Pachyrhinosaurus, Avaceratops, Einiosaurus, Albertaceratops, and Achelousaurus. 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. Dodson (1996) found enough variation between Centrosaurus, Styracosaurus, and Monoclonius to warrant seperate genera, and that Styracosaurus resembled Centrosaurus more closely than either resembled Monoclonius. Dodson also believes one species of Monoclonius, "M". nasicornis, may actually have been a female Styracosaurus.[3]
Origins
The exact origins of Styracosaurus were not understood for many years because fossil evidence for early ceratopsians was sparce. The discovery of Protoceratops, in 1922, shed some light on early ceratopsid relationships,[4] but several decades passed before additional finds came to light. However, fresh discoveries in the late 1990s and 2000s, including Zuniceratops, the earliest known ceratopsian with brow horns, and Yinlong, the first known Jurassic ceratopsian, in 2005, 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 a Jurassic origin for the group in Asia, and the appearance of truly horned ceratopsians by the beginning of the late Cretaceous in North America.[5]
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) and named by 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 m high at the hips.[6]
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 found in the Judith River formation, near Steveville, Alberta. Brown and Schlaikjer compared the finds, and, though they allowed that both specimens were from the same geological formation and from the same general locality, they considered the specimen sufficiently distinct from the holotype to warrant erecting a new genus, and described the fossils as Styracosaurus parksi. Among the differences between the specimens cited by Brown and Schlaikjer were a jugal quite different from that of S. albertensis, and smaller caudal vertebrae. S. parksi also had a more robust jaw, a shorter dentary, and the frill differed in shape from that of the type species.[7] However, Peter Dodson (1996) states that much of the skull consisted of plaster reconstruction, and the original 1937 paper did not illustrate the actual skull bones.[6] 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 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 one confirmed bonebed (bonebed 42) in Dinosaur Provincial Park has also been explored. That site contains numerous pieces of skulls such as horncores, jaws and frill pieces.
The third currently recognised species, S. ovatus, from Montana, was described by Gilmore in 1930. The fossil material is limited 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 were also only two sets of spikes on each side of the frill.
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, may be a specimen of Monoclonius, but the fossils, a partial snout and nasal horn core, are fragmentary. S. makeli, described by amateur paleontologists Stephen and Sylvia Czerkas in 1990, is now considered a specimen of Einiosaurus. "S. borealis" is S. parksi.
Paleobiology
Styracosaurus are often depicted in popular culture as herding animals, although no solid evidence suggests that they lived in groups. All Styracosaurus specimens have been found in isolation, although the closely-related Centrosaurus has been found in bonebeds containing multiple individuals.
Dentition and diet
Stegosaurus were herbivorous dinosaurs; they probably fed mostly on low growth because of the position of the head. They may, however, have been able to knock down taller plants with their horns, beak, and bulk.[8][5] The jaws were tipped with a deep, narrow beak, believed to have been better at grasping and plucking than biting.[9]
Ceratopsid teeth, including those of Styracosaurus, were arranged in groups called batteries. Older teeth on top were continually replaced by new teeth underneath; this occurred throughout the life of the animal. Some scientists have suggested ornithopods like Styracosaurus ate palms and cycads,[10] while others have suggested ferns.[11] One author has proposed that Late Cretaceous ceratopsians may have eaten the leaves and twigs of angiosperm trees based on a study of the jaw muscles of Triceratops, Chasmosaurus, and Styracosaurus.[6]
Horns and frill
The most obvious features of Styracosaurus were their large horns and frills. The function of these facial adornments has been the subject of debate ever since the first specimen of Styracosaurus was discovered.
Early in the 20th Century, paleontologist R. S. Lull put forth the theory that the frills of ceratopsian dinosaurs acted as anchor points for their jaw muscles.[12] Dodson (1996) supported this idea and created detailed diagrams of possible muscle attachments in the frills of Styracosaurus and Chasmosaurus. C.A. Forster, however, found no evidence of large muscle attachments on the frill bones.[13]
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.[14]
The large frill on Styracosaurus and related genera also may have helped to increase body area to regulate body temperature.[15] A similar theory has been proposed regarding the plates of Stegosaurus,[16] although this use alone would not account for the bizarre and extravagant variation seen in different members of the Ceratopsidae.[5] 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.[17][13][18] Evidence that visual display was important, either in courtship or in other social behaviour, 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 behaviour.[19]
In popular culture
Styracosaurus has appeared in many dinosaur films, most notably The Son of Kong, The Valley of Gwangi, and Disney's Dinosaur. The video games Styracosaurus has been featured in include: Vivendi Universal's Jurassic Park: Operation Genesis, Banjo-Tooie, Turok: Evolution, Turok 2: Seeds of Evil, Zoo Tycoon, and Zoo Tycoon 2: Dino Danger Pack. Styracosaurus has appeared in several cartoons and animes, including Dinosaucers and Zoids.
The Japanese Beast Wars Transformer Killerpunch is a Styracosaurus, and is a slight remold of Triceradon/Guiledart.
References
- ^ a b Lambert, D. (1993). The Ultimate Dinosaur Book. Dorling Kindersley: New York, 152-167. ISBN 1-56458-304-X.
- ^ Paul, Gregory (September 2000). "Forelimb posture in neoceratopsian dinosaurs: implications for gait and locomotion". Paleobiology. 26 (3). BioOne: 450–465. doi:10.1666/0094-8373(2000)026<0450:FPINDI>2.0.CO;2. Retrieved 2007-02-25.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ Dodson, P. (1996). The Horned Dinosaurs. Princeton University Press:Princeton, New Jersey, p. 197-199. ISBN 0-691-02882-6.
- ^ Dodson, P. (1996). The Horned Dinosaurs. Princeton University Press:Princeton, New Jersey, p. 244. ISBN 0-691-02882-6.
- ^ a b c 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.
- ^ a b c Dodson, Peter (1996). The Horned Dinosaurs. Princeton: Princeton University Press. pp. 165–169. ISBN 0-691-05900-4.
{{cite book}}: Cite has empty unknown parameter:|coauthors=(help) - ^ Brown, Barnum (1937). "The skeleton of Styracosaurus with the description of a new species". American Museum novitates. no. 955. New York City : The American Museum of Natural History: 12. doi:http://hdl.handle.net/2246/2191. Retrieved 2007-03-29.
{{cite journal}}:|volume=has extra text (help); Check|doi=value (help); External link in|doi=|coauthors=ignored (|author=suggested) (help) - ^ Tait J., and Brown, B. (1928). How the Ceratopsia carried and used their head. Transactions of the Royal Society of Canada. 22:13–23.
- ^ Ostrom, J. H. (1966). "Functional morphology and evolution of the ceratopsian dinosaurs". Evolution. 20 (3): pp. 290–308.
{{cite journal}}:|pages=has extra text (help) - ^ Weishampel, D. B. (1984). Evolution of jaw mechanisms in ornithopod dinosaurs. Advances in Anatomy, Embryology, and Cell Biology 87:1-110.
- ^ 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.
- ^ Lull, R. S. (1908). The cranial musculature and the origin of the frill in the ceratopsian dinosaurs. American Journal of Science 4(25):387–399.
- ^ a b 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.
- ^ 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.
- ^ Wheeler, P.E. (1978). "Elaborate CNS cooling structures in large dinosaurs". Nature (275): 441–443.
- ^ Farlow, J. O., Thompson, C. V., and Rosner, D. E. (1976). "Plates of the dinosaur Stegosaurus: Forced convection heat loss fins?". Science. 192: pp. 1123–1125.
{{cite journal}}:|pages=has extra text (help)CS1 maint: multiple names: authors list (link) - ^ Davitashvili L (1961). The Theory of sexual selection. Izdatel'stvo Akademia nauk SSSR. pp. p. 538.
{{cite book}}:|pages=has extra text (help) - ^ Cite error: The named reference
TML90was invoked but never defined (see the help page). - ^ Farlow, J. O., and Dodson, P. (1975). "The behavioral significance of frill and horn morphology in ceratopsian dinosaurs". Evolution. 29 (2): pp. 353–361.
{{cite journal}}:|pages=has extra text (help)CS1 maint: multiple names: authors list (link)
- Dodson, P. (1996). The Horned Dinosaurs. Princeton University Press, Princeton, New Jersey. ISBN 0-691-05900-4.
- Liddell & Scott (1980). Greek-English Lexicon, Abridged Edition. Oxford University Press, Oxford, UK. ISBN 0-19-910207-4.
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