In Depth
Struthiomimus remains were actually known all the way back to 1901, but were interpreted by Lawrence Lambe to belong to Ornithomimus altus, the first ornithomimid to be named. In 1917 however, Henry Fairfield Osborn (the man who is perhaps best remembered for naming Tyrannosaurus) identified key differences in the bones, especially the hands and renamed the remains as a new genus, Struthiomimus. Despite the difference, Struthiomimus and Ornithomimus are still very much like one another, and between them they seem to have been the two most common types of ornithomimid active in North America.
The signature feature of Struthiomimus is the hand size in that the hands are proportionately longer in relation to the rest of the arm than in other known ornithomimid genera. With this feature in mind, it’s possible that Struthiomimus may have had a greater reliance upon using its hands for feeding, although like with other ornithomimids this, what Struthiomimus ate remains a mystery to be certain.
Like with its close relatives, Struthiomimus had a keratinous toothless beak in life, which could have been used for a variety of different feeding strategies. Osborn speculated that Struthiomimus was a selective browser that used this narrow beak to pick out the most nutritious parts of plants. The hands could also have been used to reach around branches and pull down more of the plant to be within range of the mouth. Other palaeontologists however have speculated that Struthiomimus may have been more insectivorous, using the beak to pick out large grubs and insects, while others have gone even further by suggesting that small reptiles like snakes and lizards as well as small primitive mammals may have also been tackled. Today however most prefer to think of Struthiomimus as an omnivore which could adapt to whatever food was available.
Omnivory however is the most likely dietary preference for a relatively small dinosaur like Struthiomimus. The strictly herbivore niche would have been filled by large numbers of ceratopsian dinosaurs like Chasmosaurus as well as other dinosaur types like ankylosaurs such as Euoplocephalus and hadrosaurs like Edmontonsaurus. The predatory niche would have also been filled by large tyrannosaurs such as Albertosaurus as well as smaller dromaeosaurs like Dromaeosaurus. But by moving between these groups and adapting to different conditions, Struthiomimus would be able to coexist with these other forms, perhaps going some way to explain the large number of ornithomimid remains in general.
The classification of Struthiomimus is a little muddled with many of the named species that were named throughout the twentieth century being reassigned to other ornithomimid genera. The 2010 renaming of Ornithomimus edmontonicus to Struthiomimus edmontonicus by Gregory S. Paul has so far not found wide acceptance amongst palaeontologists and as such edmontonicus usually remains attributed to Ornithomimus.
Further Reading
– Skeletal adaptations of Ornitholestes, Struthiomimus, Tyrannosaurus. – Bulletin of the American Museum of Natural History 35(43):733-771 – H. F. Osborn – 1916. – 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. – W. A. Parks – 1926. – Struthiomimus samueli, a new species of Ornithomimidae from the Belly River Formation of Alberta. – University of Toronto Studies, Geology Series 26:1-24. – W. A. Parks – 1928. – A new specimen of Struthiomimus altus from Alberta, with comments on the classificatory characters of Upper Cretaceous ornithomimids. – Canadian Journal of Earth Sciences 18:518-526. – E. L. Nicholls & A. R. Russel – 1981.
