Struthiomimus

Taxobox
name = "Struthiomimus"
fossil_range = Late Cretaceous

---

image_width = 250px
image_caption = Illustration of "Struthiomimus altus"
regnum = Animalia
phylum = Chordata
classis = Sauropsida
superordo = Dinosauria
ordo = Saurischia
subordo = Theropoda
familia = Ornithomimidae
genus = "Struthiomimus"
genus_authority = Osborn, 1917
subdivision_ranks = Species
subdivision =
* "S. altus" (Lambe, 1902 [originally "Ornithomimus altus"] ) (type)
* "S. sedens" (Marsh, 1892 [originally "Ornithomimus sedens"] )

"Struthiomimus" (meaning "ostrich mimic", from the Greek "στρουθιον"/"strouthion" meaning "ostrich" and "μιμος"/"mimos" meaning "mimic" or "imitator") is a genus of ornithomimid dinosaur from the late Cretaceous of Alberta, Canada. It was a long-legged, ostrich-like dinosaur.

The bipedal "Struthiomimus" stood about 4.3 meters long (14 ft) and 1.4 meters (4.6 ft) tall at the hips and weighed around 150 kilograms (330 lb).cite book |last=Paul |first=Gregory S. |title=Predatory Dinosaurs of the World |year=1988 |publisher=Simon & Schuster |location=New York |isbn=0-671-61946-2 |chapter="Ornithomimus altus" |pages=pp. 387–389 ] "Struthiomimus" is one of the more common small dinosaurs in the Dinosaur Provincial Park; its abundance suggests that it was a herbivore or omnivore rather than a carnivore.Barrett, Paul M. (2005). " [http://www.blackwell-synergy.com/doi/abs/10.1111/j.1475-4983.2005.00448.x?cookieSet=1&journalCode=pala The diet of ostrich dinosaurs (Theropoda: Ornithomimosauria)] ". "Palaeontology" 48 (2), 347–358. DOI:10.1111/j.1475-4983.2005.00448.x]

Like many other dinosaur genera discovered in the 1800s, the history of "Struthiomimus" is convoluted. The first known fossils of "Struthiomimus" were named "Ornithomimus sedens" by Othniel Charles Marsh in 1892, and a subsequent species was named "O. altus" by Lawrence Lambe in 1902. It wasn't until 1917 that Henry Fairfield Osborn named "Struthiomimus" from fossils discovered in 1914 from the Red Deer River site in Alberta.

Description

"Struthiomimus" had a typical build and skeletal structure for an ornithomimid, differing from genera like "Ornithomimus" and "Dromiceiomimus" in proportions and anatomical details.cite book |last=Paul |first=Gregory S. |title=Predatory Dinosaurs of the World |year=1988 |publisher=Simon & Schuster |location=New York |isbn=0-671-61946-2 |chapter=Genus "Ornithomimus" |pages=pp. 384–394] It is known from several skeletons and skulls,cite book |last=Currie |first=Philip J. |authorlink=Philip J. Currie |editors=Currie, Phillip J., and Koppelhus, Eva (eds.) |title=Dinosaur Provincial Park: A Spectacular Ancient Ecosystem Revealed |chapter=Theropods, Including Birds |year=2005 |publisher=Indiana University Press |location=Bloomington |pages=pp. 367-397 |isbn=0-253-34595-2 ] and its size is estimated as about 4.3 meters long (14 ft) and 1.4 meters (4.6 ft) tall at the hips, with a weight of around 150 kilograms (330 lb). As with other ornithomimids, it had a small slender head on a long neck (which made up about 40% of the length of the body in front of the hips). Its eyes were large and its jaws were toothless. Its vertebral column had ten neck vertebrae, sixteen back vertebrae, six hip vertebrae, and an unknown number of tail vertebrae.cite book |last=Makovicky |first=Peter J. |coauthors=Kobayashi, Yoshitsugu; and Currie, Philip J. |year=2004 |chapter=Ornithomimosauria |editor=Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.) |title=The Dinosauria |edition=2nd |publisher=University of California Press |location=Berkeley |isbn=0-520-24209-2 |pages=137-150] The tail was stiff and was probably used for balance.cite journal |last=Osborn |first=Henry Fairfield |authorlink=Henry Fairfield Osborn |title=Skeletal adaptations of "Ornitholestes", "Struthiomimus", "Tyrannosaurus" |journal=Bulletin of the American Museum of Natural History |volume=35 |pages=733–771 |year=1917 |url=http://digitallibrary.amnh.org/dspace/bitstream/2246/1334/1/B035a43.pdf |format=pdf]

"Struthiomimus" had long slender arms and hands, with immobile forearm bones but limited opposability between the first finger and the other two.cite journal |last=Nicholls |first=Elizabeth L. |coauthors=and Russell, Anthony P. |year=1985 |title=Structure and function of the pectoral girdle and forelimb of "Struthiomimus altus" (Theropoda: Ornithomimidae) |journal=Palaeontology |volume=28 |pages=643–677] It had the longest hands of any ornithomimid, with particularly long claws. The three fingers were roughly the same length, and the claws were only slightly curved; Henry Fairfield Osborn, describing a skeleton in 1917, compared the arm to that of a sloth. Its shin was longer than its thigh, a cursorial feature. Among ornithomimids, though, its legs were only moderately elongate. Its feet were elongate, and the metatarsals were tightly appressed, with three toes tipped by claws with very slight curvature.

"Struthiomimus", being a member of Coelurosauria, probably had feathers.

Discovery and species

In 1901, Lawrence Lambe found some incomplete remains and named them "Ornithomimus altus", placing them in the same genus as material earlier described by Othniel Charles Marsh in 1890. The specific name "altus" is from Latin, meaning "lofty" or "noble". However, in 1914, a nearly complete skeleton was discovered by Barnum Brown at the Red Deer River site in Alberta, and officially described as the separate genus "Struthiomimus" by Henry Fairfield Osborn in 1917."Struthiomimus altus" comes from the Late Campanian (Judithian age) Dinosaur Park Formation. A species of "Struthiomimus" is also known from the Late Campanian/Early Maastrichtian (Edmontonian age) Horseshoe Canyon Formation.Longrich, N. (2008). "A new, large ornithomimid from the Cretaceous Dinosaur Park Formation of Alberta, Canada: Implications for the study of dissociated dinosaur remains." "Palaeontology, 54(1): 983-996.] Because dinosaur fauna show rapid turnover, it is possible that these younger "Struthiomimus" specimens will prove to be a species distinct from "S. altus", though no new name has been given to them. "Struthiomimus" specimens from the Hell Creek Formation are larger (similar to "Gallimimus" in size) and tend to have straighter and more elongate hand claws, similar to those seen in "Ornithomimus". They most likely represent a separate species of "Struthiomimus", named "Struthiomimus sedens" (again, originally named as a species of "Ornithomimus" by Marsh, in 1892).Marsh, O.C. (1892). "Notice of new reptiles from the Laramie Formation." "American Journal of Science", Series 3, 43: 449–453.]

Classification

clade| style=font-size:80%;line-height:80%
label1=Ornithomimosauria
1=clade
1="Pelecanimimus"
label2=unnamed
2=clade
1="Archaeornithomimus"
2="Shenzhousaurus"
label3=unnamed
3=clade
1="Harpymimus"
label2=unnamed
2=clade
1="Garudimimus"
label2=Ornithomimidae
2=clade
1="Struthiomimus"
2="Gallimimus"
label3= unnamed
3=clade
1="Ornithomimus"
2="Anserimimus" The cladogram presented here follows the one recovered by Turner, Clarke, Ericson and Norell, 2007.Turner, A.H., Pol, D., Clarke, J.A., Erickson, G.M., and Norell, M. (2007). "Supporting online material for: A basal dromaeosaurid and size evolution preceding avian flight". "Science", 317: 1378-1381. doi:10.1126/science.1144066 ( [http://www.sciencemag.org/cgi/data/317/5843/1378/DC1/1?ck=nck supplement] )] Clade names follow definitions provided by Sereno, 2005.Sereno, P. C. 2005. [http://www.taxonsearch.org/Archive/stem-archosauria-1.0.php Stem Archosauria—TaxonSearch] [version 1.0, 2005 November 7] ]

"Struthiomimus" is a member of the family Ornithomimidae, a group which also includes "Anserimimus ", "Archaeornithomimus", "Dromiceiomimus", "Gallimimus", "Ornithomimus", and "Sinornithomimus".

Just as the fossil remains of "Struthiomimus" were incorrectly assigned to "Ornithomimus", the superfamily that "Struthiomimus" belongs to, the Ornithomimosauria, also underwent many changes over the years. For example, O.C. Marsh initially included "Struthiomimus" in the Ornithopoda, a large clade of dinosaurs not closely related to theropods.O. C. Marsh. 1890. Additional characters of the Ceratopsidae, with notice of new Cretaceous dinosaurs. American Journal of Science 39:418-426] Five years later, Marsh classified "Struthiomimus" in the Ceratosauria.O. C. Marsh. 1895. On the affinities and classification of the dinosaur reptiles. American Journal of Science.] O. C. Marsh. 1896. The dinosaurs of North America. United States Geological Survey, 16th Annual Report, 1894-95 55:133-244] In 1891, Baur placed the genus within Iguanodontia.G. Baur. 1891. Remarks on the reptiles generally called Dinosauria. The American Naturalist 25 (293) :434-454] As late as 1993, "Struthiomimus" was referred to Oviraptorosauria.D. A. Russell and Z.-M. Dong. 1993. The affinities of a new Theropod from the Alxa Desert, Inner Mongolia, People's Republic of China. Canadian Journal of Earth Sciences 30 (10-11) :2107-2127] However, by the 1990s, there were numerous studies that placed "Struthiomimus" within Coelurosauria.J. A. Gauthier and K. Padian. 1985. Phylogenetic, functional, and aerodynamic analyses of the origin of birds and their flight. In M. K. Hecht, J. H. Ostrom, G. Viohl, and P. Wellnhofer (eds.), The Beginnings of Birds: Proceedings of the International Conference Archaeopteryx, Eichstätt 1984. Freunde des Jura-Museums Eichstätt, Eichstätt 185-197] F. E. Novas. 1992. The evolution of carnivorous dinosaurs. In J. L. Sanz and A. D. Buscalioni (eds.), The Dinosaurs and Their Environment Biotic: Proceedings of the Second Year of Paleontology in Cuenca. Institute "Juan Valdez", Cuenca, Argentina 126-163] P. C. Sereno, J. A. Wilson, H. C. E. Larsson, D. B. Dutheil, and H.-D. Sues. 1994. Early Cretaceous dinosaurs from the Sahara. Science 266 (5183) :267-271] P. J. Makovicky, Y. Kobayashi, and P. J. Currie. 2004. Ornithomimosauria. In D. B. Weishampel, P. Dodson, & H. Osmólska (eds.), The Dinosauria (second edition). University of California Press, Berkeley 137-150]

Recognizing the difference between ornithomimids and other theropods, Rinchen Barsbold placed ornithomimids within their own infraorder, Ornithomimosauria, in 1976.R. Barsbold. 1976. K evolyutsii i sistematike pozdnemezozoyskikh khishchnykh dinozavrov [The evolution and systematics of late Mesozoic carnivorous dinosaurs] . In N. N. Kramarenko, B. Luvsandansan, Y. I. Voronin, R. Barsbold, A. K. Rozhdestvensky, B. A. Trofimov & V. Y. Reshetov (eds.), Paleontology and Biostratigraphy of Mongolia. The Joint Soviet-Mongolian Paleontological Expedition, 3:68-75 Transactions] The constituency of Ornithomimidae and Ornithomimosauria varied with different authors. Paul Sereno, for example, used Ornithomimidae to include all ornithomimosaurians in 1998, but subsequently changed to a more exclusive definition (advanced ornithomimosaurs) within Ornithomimosauria,P.C. Sereno. 1998. A rationale for phylogenetic definitions, with application to the higher-level taxonomy of Dinosauria. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 210 (1) :41-83] a classification scheme that was adopted by other authors at the beginning of the current century.

Paleobiology

Diet

There has been much discussion about the feeding habits of "Struthiomimus". Because of its straight-edged beak, "Struthiomimus" may have been an omnivore. Some theories suggest that it may have been a shore-dweller and may have been a filter feeder. Some paleontologists noted that it was more likely to be a carnivore because it is classified within the otherwise carnivorous theropod group. [cite journal|author=Osmólska H, Roniewicz E & Barsbold R|year=1972|title=A new dinosaur, "Gallimimus bullatus" n. gen.,n. sp. (Ornithomimidae) from the Upper Cretaceous of Mongolia|journal=Paleontol. Polonica|volume=27|pages=103–143] [cite journal|author=Russell D|year=1972|title=Ostrich dinosaurs from the Late Cretaceous of Western Canada|journal=Canadian Journal of Earth Sciences|volume=9|pages=375–402] This theory has never been discounted, but Osborn, who described and named the dinosaur, proposed that it probably ate buds and shoots from trees, shrubs and other plants, using its forelimbs to grasp branches and its long neck to enable it accurately to select particular items. This herbivorous diet is further supported by the unusual structure of its hands. The second and third fingers were of equal length, could not function independently, and were probably bound together by skin as a single unit. This indicates that the hand was used as a "hook", for bringing branches or fern fronds within reach.

peed

The legs (hind limbs) of "Struthiomimus" were long, powerful and seemingly well-suited to rapid running, much like an ostrich. The supposed speed of "Struthiomimus" was, in fact, its main defense from predators (although it may also have been able to lash out with its hind claws when cornered), such as the dromaeosaurids (e.g. "Saurornitholestes" and "Dromaeosaurus") and tyrannosaurs (e.g. "Daspletosaurus" and "Gorgosaurus"), which lived at the same time. It is estimated to have been able to run at speeds between 50 to 80 km/h (30 to 50 mph).Paul, regarding his comparative speed estimates, notes that "... just how swift is swift? In hard, precise measure, this can be a real can of worms; for just how fast living animals run is not well known." (Paul, G.S. 1988. "Predatory Dinosaurs of the World". New York: Simon & Schuster.)]

Posture

Early restorations depict a posture reminiscent of the "walking tripod" postures of "Tyrannosaurus" and "Iguanodon", before the later, more balanced depictions with stiffened horizontal tails and bodies were widely accepted. This newer view creates an image much more reminiscent of modern flightless birds, such as the ostrich to which this dinosaur's name refers.

Popular culture

The best-preserved skeleton of "Struthiomimus" is currently on display at the American Museum of Natural History, in Manhattan, New York, while the best-preserved skull is currently on display at the Royal Tyrrell Museum of Palaeontology, in Drumheller, Alberta, Canada.

"Struthiomimus" has appeared in several dinosaur-related films and television programs, such as the egg-napping villains in "". They played a prominent role in the Disney animated film "Dinosaur", and in 1985, "Struthiomimus" was featured in "Dinosaur!, a CBS television documentary hosted by Christopher Reeve. In a stop-motion animation sequence, a "Struthiomimus" was shown feeding on hadrosaurid eggs and escaping the angry mother, only to be preyed upon by a pair of "Deinonychus" moments later (though in reality, "Deinonychus" lived in the early Cretaceous Period and was not a contemporary of "Struthiomimus"). "Struthiomimus" toys were included in the Dino-Riders line by Tyco and was later re-released in the Smithsonian toy line.

References

*Russell, D. A. (1969). "A new specimen of "Stenonychosaurus" from the Oldman Formation (Cretaceous) of Alberta". "Canadian Journal of Earth Sciences" 6: 595-612.
*Cranfield, I. (2004). "The Illustrated Directory of Dinosaurs and other Prehistoric Creatures" (pp. 30-33). Greenwich Editions. ISBN 0-86288-662-7.