Struthiomimus

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

The bipedal *Struthiomimus* stood about 14 ft long and 4.6 ft tall at the hips and weighed around 330 pounds. *Struthiomimus* is one of the more common small dinosaurs in the Provincial Park; its abundance suggests that it was a herbivore or omnivore rather than a carnivore.

Like many other dinosaur genera discovered in the 19th century, 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 size and anatomical details. It is known from some skeletons and skulls, and its size is about 14 ft long and 4.6 ft tall at the hips, with a weight of around 330 pounds.  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 had no teeth. Its spine had 10 neck vertebrae, 13 back vertebrae, 6 hip vertebrae, and about 35 tail vertebrae. The tail was stiff and was likely used for balance.

*Struthiomimus* had long arms and hands, with still forearm bones and limited opposability between the first finger and the other two. It had the longest hands of any ornithomimid, with particularly long claws. The three fingers were roughly the same length, and the claws had a slight curve; Henry Fairfield Osborn, describing a skeleton in 1917, said the arm was like that of a sloth. Its shin was longer than its thigh, a feature for running. Among ornithomimids, though, its legs were of moderate length.  Its feet were long, with three toes tipped by claws with a slight curve.

*Struthiomimus*, being a relative of the definitely plumed *Ornithomimus*, was most likely feathered to some extent.

## History

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 subgenus *Struthiomimus* by Henry Fairfield Osborn in 1917.

In years to come William Arthur Parks named four more species of *Struthiomimus*: *Struthiomimus brevetertius* Parks 1926, *Struthiomimus samueli* Parks 1928, *Struthiomimus currellii* Parks 1933 and *Struthiomimus ingens* Parks 1933. These are now thought to either come from to *Dromiceiomimus* or to *Ornithomimus*.

In 1997 Donald Glut mentioned the name *Struthiomimus lonzeensis*. This was probably a mistake for *Ornithomimus lonzeensis*{C
(Dollo 1903) Kuhn 1965. {C
*Struthiomimus altus* comes from the Dinosaur Park Formation and a species of *Struthiomimus* is known from the Horseshoe Canyon Formation. Since dinosaur fauna show rapid turnover, it could be that these younger *Struthiomimus* specimens will prove to be a species distinct from *S. altus*, though they have no new name. *Struthiomimus* specimens from the Hell Creek Formation are larger (similar to *Gallimimus* in size) and tend to have straighter and longer hand claws, like those seen in *Ornithomimus*. They most likely represent a separate species of *Struthiomimus*, in 2001 by James Orville Farlow named *Struthiomimus sedens* (again, first named as a species of *Ornithomimus* by Marsh, in 1892).

In 2010 Gregory S. Paul renamed *Ornithomimus edmontonicus* Sternberg 1933 to a *Struthiomimus edmontonicus*, but this has found no acceptance by other workers.

## Classification

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

Just as the bones of *Struthiomimus* were wrongly assigned to *Ornithomimus*, the larger group that *Struthiomimus* belongs to, the Ornithomimosauria, also went thorugh many changes over the years. For example, O.C. Marsh at first included *Struthiomimus* in the Ornithopoda, a large clade of dinosaurs not closely related to theropods.  Five years later, Marsh classified Struthiomimus in the Ceratosauria.   In 1891, Baur placed the genus in Iguanodontia. As late as 1993, *Struthiomimus* was referred to Oviraptorosauria. However, by the 1990s, there were a lot of studies that placed *Struthiomimus* in Coelurosauria.

In 1976, Rinchen Barsbold saw the difference between ornithomimids and other theropods, and placed ornithomimids in their own infraorder, Ornithomimosauria. 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, a classification scheme that other authors took up at the beginning of the current century.

## Paleobiology

### Diet

There has been much talk of what *Struthiomimus* ate. Its straight-edged beak shows that *Struthiomimus* may have been an omnivore. Some theories suggest that it may have shore-dweller and may have been a filter feeder.  Some paleontologists note that it was more likely that it ate meat as it is classified in the otherwise meat-eating theropod group.  This theory has not 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 front limbs to grasp branches and its long neck to let it take particular things. This plant-based diet is backed up by the strange structure of its hands. The second and third fingers were of the same length, could not work on their own, and were probably bound together by skin as a single unit. The structure of the shoulder girdle did not allow a high elevation of the arm nor was optimised for a low reach. The hand could not be fully flexed for a grasping motion or spread for raking. This is a sign that the hand was used as a "hook" or "clamp", to bring branches or fern fronds at shoulder height within reach.

### Speed

The legs (hind limbs) of *Struthiomimus* were long, strong, and seemed to be well-suited to run fast, much like an ostrich. The supposed speed of *Struthiomimus* was, in fact, its main defense from predators (though it may also have been able to lash out with its hind claws when trapped), such as the dromaeosaurids (e.g. *Saurornitholestes* and *Dromaeosaurus*) and tyrannosaurs (e.g. *Daspletosaurus* and *Gorgosaurus*), which lived at the same time. It is thought to have been able to run at speeds from 31 to 50 mph.

### Posture

*Struthiomimus* was one of the first theropods pictured from the start with a horizontal posture. Osborn in 1916 let the animal intentionally be drawn with a raised tail. This newer view created an image much more similar to modern flightless birds, such as the ostrich to which this dinosaur's name comes from, but would only much later be accepted for all theropods.

## External links

* Details on DinoRuss *Struthiomimus*
* *Struthiomimus* illustrations in The Natural History Museum's Dino Directory

1. ↑ Paul, Gregory S. (1988). "Ornithomimus altus". Predatory Dinosaurs of the World. New York: Simon & Schuster. pp. 387–389. ISBN 0-671-61946-2.
2. ↑ Barrett, Paul M. (2005). "The diet of ostrich dinosaurs (Theropoda: Ornithomimosauria)". Palaeontology 48 (2), 347–358. DOI:10.1111/j.1475-4983.2005.00448.x
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10. ↑ Osborn, Henry Fairfield (1917). "Skeletal adaptations of Ornitholestes, Struthiomimus, Tyrannosaurus" (pdf). Bulletin of the American Museum of Natural History 35: 733–771.
11. ↑ Parks, W.A., 1926, "*Struthiomimus brevetertius* - A new species of dinosaur from the Edmonton Formation of Alberta", *Transactions of the Royal Society of Canada*, series 3. **20**(4): 65-70
12. ↑ Parks, W.A., 1928, "*Struthiomimus samueli*, a new species of Ornithomimidae from the Belly River Formation of Alberta", *University of Toronto Studies, Geology Series*. **26**: 1-24
13. ↑ Parks, W.A., 1933, "New species of dinosaurs and turtles from the Upper Cretaceous formations of Alberta", *University of Toronto Studies, Geological Series*, **34**: 1-33
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25. ↑ 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
26. ↑ 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
27. ↑ 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
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30. ↑ Makovicky, Peter J.; Kobayashi, Yoshitsugu; and Currie, Philip J. (2004). "Ornithomimosauria". In Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.). The Dinosauria (2nd ed.). Berkeley: University of California Press. pp. 137–150. ISBN 0-520-24209-2.
31. ↑ Osmólska H, Roniewicz E & Barsbold R (1972). "A new dinosaur, Gallimimus bullatus n. gen.,n. sp. (Ornithomimidae) from the Upper Cretaceous of Mongolia". Paleontol. Polonica 27: 103–143.
32. ↑ Russell D (1972). "Ostrich dinosaurs from the Late Cretaceous of Western Canada". Canadian Journal of Earth Sciences 9 (4): 375–402. doi:10.1139/e72-031.
33. ↑ Paul, Gregory S. (1988). "Genus Ornithomimus". Predatory Dinosaurs of the World. New York: Simon & Schuster. pp. 384–394. ISBN 0-671-61946-2.
34. ↑ Nicholls, Elizabeth L.; and Russell, Anthony P. (1985). "Structure and function of the pectoral girdle and forelimb of Struthiomimus altus (Theropoda: Ornithomimidae)". Palaeontology 28: 643–677.
35. ↑ 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.)
36. ↑ Osborn, Henry Fairfield (1917). "Skeletal adaptations of Ornitholestes, Struthiomimus, Tyrannosaurus" (pdf). Bulletin of the American Museum of Natural History 35: 733–771.