Styracosaurus
| Styracosaurus | ||||||||||||
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Live reconstruction of Styracosaurus |
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| Temporal occurrence | ||||||||||||
| Upper Cretaceous (late Campanium ) | ||||||||||||
| 76.4 to 72 million years | ||||||||||||
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| Scientific name | ||||||||||||
| Styracosaurus | ||||||||||||
| Lambe , 1913 | ||||||||||||
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Styracosaurus is a genus of pelvic dinosaurs from the group of Ceratopsidae within the Ceratopsia . This dinosaur, characterized by its nasal horn and its horns on the edge of the neck shield, lived in the Upper Cretaceous in what is now North America .
features
Styracosaurus reached a length of around 5.5 meters and an estimated weight of 3 tons, making it a medium-sized Ceratopsidae. His physique resembled that of the other members of this group, they were sturdy animals with large, massive skulls and powerful limbs, the hind legs being significantly longer than the front legs.
Styracosaurus is counted among the Centrosaurinae , which are usually characterized by a long nasal horn, short or missing super-eye horns and a short neck shield. The skull was very large, up to 2 meters in length (including the neck shield). The snout was pointed and parrot-like, it was formed as with all Ceratopsia from the rostral bone (in front of the upper jaw) and the predentals (in front of the lower jaw). The cheek region was expansive, making the skull almost triangular from above. As with all Ceratopsidae, the dentition consisted of tooth batteries, these are teeth arranged in rows, which were replaced by the following tooth when they were worn out. The occlusal surfaces of the dentition were almost vertical, which suggests that the teeth were mainly used for cutting.
The nasal bone carried a nasal horn up to 50 centimeters long, the longest known of all Centrosaurinae. The neck shield typical of the Ceratopsidae was formed from the parietal and scaled bones and had two paired openings. There were four or six long spines on the rear edge of the shield, and there were other small bony bumps or spines on the edge of the shield.
The first cervical vertebrae had fused to form the syncervical . There were 46 caudal vertebrae , the highest known number of all ceratopsids. The limbs were sturdy, the feet short and strong. The front feet had five and the hind feet four hoof-like toes.
Paleobiology
Some of the remains of Styracosaurus were found in bone beds , which means that the fossils of numerous animals from different ages lay together. These mass deposits could be an indication of possible life in associations; But it is also possible that in periods of drought, many otherwise solitary animals came together at watering holes and died there due to the drying up of the spring.
Horns and neck shields of the Ceratopsidae are often associated with the defense against predators. However, the rearward protruding horns from the edge of the shield may not have been very well suited for defensive purposes. The neck shield was also too thin to act as a protection against neck bites. According to today's perspective, the headdress primarily served to identify the individual species as well as to interact with conspecifics - either through display, threatening gestures or in fights. It may have been about territorial boundaries or mating privileges.
The Styracosaurus tooth batteries with the vertical occlusal surfaces were designed for a cutting, but not a grinding movement. The pointed muzzle is an indication of an ability to selectively eat food, the structure of the lower jaw indicates a high bite force. This dinosaur probably lived on tough, fibrous plants.
Discovery and naming
The fossil remains of Styracosaurus come from the Judith River Group in western North America. The finds are dated in the Upper Cretaceous (late Campanium ) to an age of about 76 to 72 million years.
The genus was first described in 1913 by Lawrence Lambe based on a find in Alberta (Canada) . The name is derived from the Greek words στύραξ / styrax (= "sting") and σαῦρος / sauros (= "lizard"). The type species is S. albertensis . In 1930, S. ovatus was described as a second species that originated in the US state of Montana . S. ovatus is only known from a part of the neck shield in which the horns at the edge of the shield were bent towards each other and not away from each other as in S. albertensis . Overall, however, the findings are too meager, so that S. ovatus was considered a nomen dubium . In 2010, McDonald and Horner described new fossil material that justified the assignment of S. ovatus to its own genus ( Rubeosaurus ). The genus Styracosaurus has since been considered monotypical again .
Systematics
Styracosaurus is classified within the Ceratopsidae in the subfamily of Centrosaurinae . Together with Centrosaurus (and possibly the little-known genus Monoclonius ) it often forms the tribe of Centrosaurini.
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| Systematic position of Styracosaurus according to Evans & Ryan (2015). |
In 2015, the family tree of the Centrosaurinae was revised by Evans & Ryan (2015) on the occasion of the first description of the Wendiceratops found in Canada . Accordingly, Styracosaurus is the sister genus to Coronosaurus , the common taxon is compared to a sister group of Centrosaurus and Spinops . In a phylogenetic analysis in 2012 it was still considered a sister species of the Coronosaurus , the Centrosaurus was considered the sister taxon of the two genera.
literature
- Peter Dodson , Catherine A. Forster, Scott D. Sampson: Ceratopsidae. 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. 494-513.
- Michael J. Ryan, Anthony P. Russell: A new centrosaurine ceratopsid from the Oldman Formation of Alberta and its implications for centrosaurine taxonomy and systematics. In: Canadian Journal of Earth Sciences. Vol. 42, No. 7, 2005, ISSN 0008-4077 , pp. 1369–1387, doi : 10.1139 / e05-029 , here p. 1370, digitized (PDF; 1.9 MB) ( Memento from February 25, 2012 in the Internet Archive ).
Web links
Individual evidence
- ^ Gregory S. Paul : The Princeton Field Guide To Dinosaurs. Princeton University Press, Princeton NJ et al. 2010, ISBN 978-0-691-13720-9 , pp. 261-262 ( online ).
- ^ AT McDonald & JR Horner: New Material of "Styracosaurus" ovatus of the Two Medicine Formation of Montana. In: MJ Ryan, BJ Chinnery-Allgeier & DA Eberth: New Perspectives on Horned Dinosaurs: The Royal Tyrrell Museum Ceratopsian Symposium , pp. 156-168, Indiana University Press, 2010. ISBN 978-0-253-35358-0 (reading sample )
- ↑ David C. Evans , Michael J. Ryan : Cranial Anatomy of Wendiceratops pinhornensis gen. Et sp. nov., a Centrosaurine Ceratopsid (Dinosauria: Ornithischia) from the Oldman Formation (Campanian), Alberta, Canada, and the Evolution of Ceratopsid Nasal Ornamentation. PLOS ONE 10 (7): e0130007. doi : 10.1371 / journal.pone.0130007 .
- ↑ Michael J. Ryan, David C. Evans, Kieran M. Shepherd: A New Ceratopsid from the Foremost Formation (Middle Campanian) of Alberta. In: Canadian Journal of Earth Sciences , Vol. 49, No. 11, 2012, ISSN 0008-4077 , pp. 1251-1262, doi : 10.1139 / e2012-056 .