|Struthiomimus altus as imagined by Irwin Christman in 1921, courtesy of copyrightexpired.com.|
|A published figure incorporating data from the ROM Struthiomimus.|
• It is one of only two specimens referred to S. altus from the Belly River Group that has a precisely documented quarry locality (Currie & Koppelhus 2005, supplementary CD).
• It is the only specimen referred to S. altus from the Belly River Group to preserve certain portions of the skull.
• It is one of only a few specimens referred to S. altus that combines the cranial, axial and appendicular elements of a single individual.
These conditions make the ROM Struthiomimus an important specimen for evaluating the diagnostic characters of S. altus, and whether it is the same species as geologically younger occurences of Struthiomimus.
When Osborn (1917) named the genus Struthiomimus, he justified its distinction from the closely related Ornithomimus partly on the basis of its lower stratigraphic occurrence, which fit the pattern he had observed in other dinosaur groups. However, subsequent discoveries enlarged the stratigraphic ranges of both taxa, and they are now known to have overlapped (Kobayashi et al. 2006, Cullen et al. 2013). The current stratigraphic range of Struthiomimus is unusually long for a dinosaur genus, and the longevity of species, or rate of species turnover within Struthiomimus, if any, is poorly understood. The Oldman and Dinosaur Park Formations were not recognized as formally distinct until the 1990s (Eberth & Hamblin 1993), and it is therefore uncertain which formation(s) much of the S. altus material from the Belly River Group was collected from. I'll also be examining fragmentary ornithomimid material from the geologically older Milk River, Foremost and Oldman Formations to see if I can detect any changes in the taxonomic content or diversity of Albertan ornithomimids preceding S. altus in the fossil record.
Cullen, T. M., Ryan, M. J., Schröder-Adams, C., Currie, P.J. and Kobayashi, Y. 2013. An ornithomimid (Dinosauria) bonebed from the Late Cretaceous of Alberta, with implications for the behavior, classification, and stratigraphy of North American ornithomimids. PLoS One 8 (3, e58853):1-9.
Currie, P. J. and Koppelhus, E. B. (eds.) 2005. Dinosaur Provincial Park: A Spectacular Ancient Ecosystem Revealed. Indiana University Press, Bloomington.
Eberth, D. A. and Hamblin, A. P. 1993. Tectonic, stratigraphic, and sedimentologic significance of a regional discontinuity in the upper Judith River Group (Belly River wedge) of southern Alberta, Saskatchewan, and nothern Montana. Canadian Journal of Earth Sciences 30: 174-200.
Kobayashi, Y., Makovicky, P., and Currie, P. 2006. Ornithomimids (Theropoda: Dinosauria) from the Late Cretaceous of Alberta, Canada. Journal of Vertebrate Paleontology 26 (3): 86A.
Osborn, H. F. 1917. Skeletal adaptions of Ornitholestes, Struthiomimus and Tyrannosaurus. Bulletin of the American Museum of Natural History 35: 733-771.
Russell, D. A. 1972. Ostrich dinosaurs from the Late Cretaceous of western Canada. Canadian Journal of Earth Sciences 9: 375-402.