Styracosaurus was a genus of herbivorous ceratopsian dinosaurs 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 may have been up to 60 centimeters (2 ft) long and 15 centimeters (6 in) wide. The function or functions of the horns and frills have been debated for many years.
Styracosaurus was a relatively 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. The skull had a beak and shearing cheek teeth arranged in continuous dental batteries, suggesting that the animal sliced up plants. 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. Two species, S. albertensis and S. ovatus are currently assigned to Styracosaurus. Other species assigned to the genus have since been reassigned elsewhere.
Description[]
Size compared to a human
Individuals of the genus Styracosaurus were approximately 5.5 meters (18 ft) long as adults and weighed around 2.7 tonnes. The skull was massive, with a large nostril, a tall straight nose horn, and a parietosquamosal frill (a neck frill) crowned with at least four large spikes. Each of the four longest frill spines was comparable in length to the nose horn, at 50 to 55 centimeters (20 to 22 inches) long. The nasal horn was estimated by Lambe at 57 centimeters (22 inches) long in the type specimen, but the tip had not been preserved. Based on other nasal horn cores from Styracosaurus and Centrosaurus, this horn may have come to a more rounded point at around half of that length.
Life restoration
Aside from the large nasal horn and four long frill spikes, the cranial ornamentation was variable. Some individuals had small hook-like projections and knobs at the posterior margin of the frill, similar to but smaller than those in Centrosaurus. Others had less prominent tabs. Some, like the type individual, had a third pair of long frill spikes. Others had much smaller projections, and small points are found on the side margins of some but not all specimens. Modest pyramid-shaped brow horns were present in subadults, but were replaced by pits in adults. Like most ceratopsids, Styracosaurus had large fenestrae (skull openings) in its frill. The front of the mouth had a toothless beak.
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, alternatively, held in a sprawling position. The most recent work has put forward an intermediate crouched position as most likely.
History[]
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Excavation of the holotype specimen
The first fossils of Styracosaurus were found in Alberta, Canada by C.M. Sternberg (from a spot now known as Dinosaur Provincial Park, in what is now called the Dinosaur Park Formation) and named by Lawrence Lambe in 1913. In 1935, a Royal Ontario Museum crew went there and found the missing jaw and most of the skeleton. These fossils show that S. albertensis was 5.5-5.8 meters in length and stood 1.65 meters high at the hips.[1] An odd trait of this first skull is that the smallest frill spike on the left side is overlapped in part at its base by the next spike. It seems that the frill was hurt at this point in life and was shortened by about 2 in. The normal shape of this part is not known since the right side of the frill was not found.[2]
Styracosaurus "parksi" skeleton, specimen AM5372
In 1915, Barnum Brown and crew, who worked for the American Museum of Natural History in New York, found a nearly complete articulated skeleton with part of a skull in the Dinosaur Park Formation, near Steveville, Alberta. Brown and Erich Maren Schlaikjer saw that while both were from the same place, they were different enough to call for a new species, and described the fossils as Styracosaurus parksi, named in honor of William Parks.[3] Some of 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 had a stronger jaw, shorter teeth, and the frill differed in shape.[3] However, most of the skull is a plaster reconstruction, and the first 1937 paper did not describe the actual skull bones.[1] It is now accepted as a specimen of S. albertensis.[2][4]
In 2006, Darren Tanke of the Royal Tyrrell Museum of Palaeontology in Drumheller, Alberta found the long lost S. parksi site.[2] Parts of the skull, clearly abandoned by the 1915 crew, were found. These were collected and it is hoped more will be found, perhaps enough to re-describe the skull and test if S. albertensis and S. parksi are the same. The Tyrrell Museum has several partial Styracosaurus skulls.[5] At least one confirmed bone bed (bonebed 42) in Dinosaur Provincial Park has also been explored (other proposed Styracosaurus bone beds instead have fossils from a mix of animals, and nondiagnostic ceratopsian remains). Bonebed 42 is known to contain numerous pieces of skulls such as horncores, jaws and frill pieces. Holotype frill of S. ovatus, which was moved to Rubeosaurus
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 part of the frill, but one odd trait is that the pair of spikes near the midline merge towards the midline, not away from it as in S. albertensis. There may have been two sets of spikes on each side of the frill, not three. The spikes are much shorter than in S. albertensis, with the longest only 11.6 in long. A 2010 review of styracosaur skulls by Ryan, Holmes, and Russell found it to be a distinct species,[2] and in 2010 McDonald and Horner placed it in its own genus, Rubeosaurus.
A lot of 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 kind of Monoclonius and based on a broken Styracosaurus-like straight nose horn, was attributed to Styracosaurus in 1915.[6] "S. makeli", mentioned informally by amateur paleontologists Stephen and Sylvia Czerkas in 1990 in a caption to an illustration, is an old name for Einiosaurus.[7] "S. borealis" is an old informal name for S. parksi.[8]
Classification[]
Styracosaurus is in the Centrosaurinae, a subfamily of large North American horned dinosaurs marked by their "[prominent nose horns, lack of brow horns, a tall, deep face, and a projection in the rear of the nostril.]"[9] Some members of the clade are Centrosaurus (from which the group takes its name),[10][11] Pachyrhinosaurus,[10][12] Avaceratops,[10] Einiosaurus,[12][13] Albertaceratops,[13] Achelousaurus,[12] Brachyceratops,[4] and Monoclonius,[10] but these last two are dubious. Due to variation from species and even individual specimens of centrosaurines, there has been much debate on which genera and species are valid, especially if Centrosaurus and/or Monoclonius are valid genera, undiagnosable, or members of the opposite sex. In 1996, Peter Dodson found enough differences between Centrosaurus, Styracosaurus, and Monoclonius to call for separate genera, and that Styracosaurus looked more like Centrosaurus than either looked like Monoclonius.[14] Dodson also believed one species of Monoclonius, M. nasicornis, may actually have been a female Styracosaurus. However, most other researchers have not accepted Monoclonius nasicornis as a female Styracosaurus, instead regarding it as a synonym of Centrosaurus apertus. While sexual dimorphism has been proposed for an earlier ceratopsian, Protoceratops, there is no firm evidence for sexual dimorphism in any ceratopsid.
Goodwin and colleagues proposed in 1992 that Styracosaurus was part of the lineage leading to Einiosaurus, Achelousaurus and Pachyrhinosaurus. This was based on a series of fossil skulls from the Two Medicine Formation of Montana. The position of Styracosaurus in this lineage is now equivocal, as the remains that were thought to represent Styracosaurus have been transferred to the genus Rubeosaurus.
Ceratopsid skull casts positioned in a phylogenetic tree, in the Natural History Museum of Utah, with Styracosaurus at the far left
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Skull of the holotype specimen
Below is a cladogram by Andrew T. McDonald in 2011.
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Origins[]
Biogeography of centrosaurine dinosaurs during the Campanian
The evolutionary origins of Styracosaurus were not known for years since fossils for early ceratopsians were sparse. When Protoceratops was found in 1922, it shed light on early ceratopsid relationships,[15] but a few decades passed till more finds filled the gap. New findings in the late 1990s and 2000s, such as Zuniceratops, the first known ceratopsian with brow horns, and Yinlong, the first known Jurassic ceratopsian, show what the ancestors of Styracosaurus may have looked like. These new findings have shed light on the origins of horned dinosaurs as a whole, and suggest that the group originated in the Jurassic in Asia, with true horned ceratopsians appearing by the start of the late Cretaceous in North America.[4]
Paleobiology[]
Restoration
Styracosaurus and other horned dinosaurs are often depicted in popular culture as herd animals. A bonebed composed of Styracosaurus remains is known from the Dinosaur Park Formation of Alberta, about halfway up the formation. This bonebed is associated with different types of river deposits. 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.
Paleontologists Gregory Paul and Per Christiansen proposed that large ceratopsians such as Styracosaurus were able to run faster than an elephant, based on possible ceratopsian trackways which did not exhibit signs of sprawling forelimbs.
Horns and frill[]
Close-up of the AM5372 skull, American Museum of Natural History
The large nasal horns and frills of Styracosaurus are one of the most distinct face adornments of all dinosaurs. Their role has been discussed since the first horned dinosaurs were found. Early in the 20th century, paleontologist R. S. Lull proposed that the frills of ceratopsians served to anchor their jaw muscles. He later noted that for Styracosaurus, the spikes would give it a formidable appearance. In 1996, Dodson supported the idea of muscle attachments in part and created detailed layouts of likely muscle attachments in the frills of Styracosaurus and Chasmosaurus, but did not subscribe to the idea that they completely filled in the fenestrae.[16] But, C.A. Forster found no evidence of large muscle attachments on the frill bones.[17]
It was long thought that ceratopsians like Styracosaurus used their frills and horns in defense against the large meat-eating dinosaurs of the time. While pitting, holes, lesions, and all kinds of harm on ceratopsid skulls are often attributed to horn damage in combat, a 2006 study found no evidence for horn thrust injuries that caused 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.[18]
The large frill on Styracosaurus and their relatives may have helped raise body area to regulate body temperature,[19] like the ears of the modern elephant. A similar theory has tried to explain the plates of Stegosaurus,[20] but just this use would not account for the bizarre arrangements seen in Ceratopsians.[21] This suggests that the main function was display.
The theory of frill use in sexual display was first proposed in 1961 by Davitashvili. This theory has gained much acceptance.[17][22] Proof that visual display was important, 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.[23]
Paleoecology[]
Depiction of the megaherbivores in the Dinosaur Park Formation, Styracosaurus third from left, with herd in the right background
Styracosaurus is known from the Dinosaur Park Formation, and was a member of a diverse and well-documented fauna of prehistoric animals that included horned relatives such as Centrosaurus and Chasmosaurus, duckbills such as Prosaurolophus, Lambeosaurus, Gryposaurus, Corythosaurus, and Parasaurolophus, tyrannosaurids Gorgosaurus, Daspletosaurus, and armored Edmontonia and Euoplocephalus.
The Dinosaur Park Formation is interpreted as a low-relief setting of rivers and floodplains that became more swampy and influenced by marine conditions over time as the Western Interior Seaway transgressed westward. The climate was warmer than present-day Alberta, without frost, but with wetter and drier seasons. Conifers were apparently the dominant canopy plants, with an understory of ferns, tree ferns, and angiosperms.
JPInstitute.com Description[]
Styracosaurus is an ancestor of the Triceratops. It lived about 10 million years before its more famous relative. Not as large as Triceratops, Styracosaurus had a row of long spikes around its frill. It also had a long horn between its eyes and nose. This plant-eater was designed to chew up the very tough leaves of low-growing plants.
The long spikes and horn would have made it difficult for the predators of that time, such as the early tyrannosaur, Albertosaurus, to take on an adult Styracosaurus. This creature had the typical features of the ceratopsian dinosaurs - a beak that would have been used to cut the leaves from the plants and a row of densely packed teeth to chew them into pulp.
There are several theories as to the use of the spikes on the frill of Styracosaurus. In addition to a defensive weapon, they may have served to make the creature look larger and more formidable or they may have been brightly colored for display during mating rituals.
Appearance in other media[]
Jurassic Park[]
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Read more Styracosaurus on Jurassic Park Wiki |
The Land Before Time[]
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Read more Styracosaurus on Land Before Time Wiki |
Links[]
References[]
- ↑ 1.0 1.1 Dodson, P. (1996). The Horned Dinosaurs: A Natural History. Princeton: Princeton University Press. pp. 165–169. ISBN 0-691-05900-4.
- ↑ 2.0 2.1 2.2 2.3 Ryan, Michael J.; Holmes, Robert; and Russell, A.P. (2007). "A revision of the late Campanian centrosaurine ceratopsid genus Styracosaurus from the Western Interior of North America". Journal of Vertebrate Paleontology 27 (4): 944–962. doi:10.1671/0272-4634(2007)27[944:AROTLC]2.0.CO;2. Retrieved 2010-08-19.
- ↑ 3.0 3.1 Template:Cite journal
- ↑ 4.0 4.1 4.2 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). Berkeley: University of California Press, pp. 494–513. ISBN 0-520-24209-2.
- ↑ Eberth, David A.; and Getty, Michael A. (2005). "Ceratopsian bonebeds: occurrence, origins, and significance". In Currie, Phillip J., and Koppelhus, Eva. Dinosaur Provincial Park: A Spectacular Ancient Ecosystem Revealed. Bloomington: Indiana University Press. pp. 501–536. ISBN 0-253-34595-2.
- ↑ Template:Cite journal
- ↑ Template:Cite book
- ↑ Template:Cite book
- ↑ Template:Cite web
- ↑ 10.0 10.1 10.2 10.3 Template:Cite book
- ↑ Template:Cite journal
- ↑ 12.0 12.1 12.2 Template:Cite journal
- ↑ 13.0 13.1 Template:Cite journal
- ↑ Dodson, P. (1996). The Horned Dinosaurs: A Natural History. Princeton University Press: Princeton, New Jersey, pp. 197–199. ISBN 0-691-02882-6.
- ↑ Dodson, P. (1996). The Horned Dinosaurs: A Natural History. Princeton University Press: Princeton, New Jersey, p. 244. ISBN 0-691-02882-6.
- ↑ Dodson, P. (1996). The Horned Dinosaurs: A Natural History. Princeton University Press: Princeton, New Jersey, p. 269. ISBN 0-691-02882-6.
- ↑ 17.0 17.1 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
- ↑ 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.
- ↑ Template:Cite journal
- ↑ Template:Cite journal
- ↑ 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). Berkeley: University of California Press, pp. 494–513. ISBN 0-520-24209-2.
- ↑ Template:Cite book
- ↑ Template:Cite journal