Monday, 4 March 2013

O is for Ornithomimus

Last week we talked about a plesiosaur, Nichollssaura, but this week we're back to dinosaurs, with 'O is for Ornithomimus'. 

Ornithomimus was a theropod dinosaur that lived during the Late Cretaceous (75-66 million years ago) of western North America, including Alberta and Saskatchewan, as well as several states in the USA. The name means 'bird-mimic', and it was named in 1890 by Othniel Charles Marsh, one of the great American fossil hunters. Ornithomimids are characterised by 3-toed feet, long necks, and birdlike elongated, toothless beaks, hence the name 'bird-mimic'. They were bipedal, walking on the two hindlimbs, and were likely fast runners. Ornithomimus had longer, more slender forelimbs than other ornithomimids and have been estimated to be 3.8 m long and 170 kg (O. edmontonicus). Evidence of feathers has been found on several specimens (including the first ever definite dinosaur feathers from Alberta), and one study suggested that Ornithomimus was covered in pennaceous feathers throughout its life [1]. They also suggested that wing-like structures were only found in adults, and may be because these are used for a mating display. Although most theropods were carnivorous, the body of this dinosaur suggests it may have been largely herbivorous. Its large eyes tell us it had good vision, and may have used that great vision to catch small mammals or lizards to supplement its diet. 
A nearly complete (missing only a small portion at the end of the tail) of Ornithomimus from the Royal Tyrrell Museum of Palaeontology. Photo by Sebastian Bergman.

Currently, the number of valid species for Ornithomimus is debated. The type species, O. velox, is still valid, while O. edmontonicus is considered by some to be Dromiceiomimus, while other studies have suggested that there is no distinction between Dromiceiomimus and Ornithomimus, and that O. edmontonicus is a valid species [2]All in all, the taxonomic (as in how many species, and what is actually Ornithomimus) history has been very complicated. 

That's it for the bird-mimic. Next week, we'll move on to an interesting thick-skulled dinosaur! Stay tuned for more!

Other 'O' dinosaurs from Alberta:
Possibly Orodromeus, but that is unconfirmed

1. Zelenitsky, D.K., et al. 2012. Feathered non-avian dinosaurs from North America provide insight into wing origins. Science 338: 510. Can be downloaded as a PDF here.
2. Mackovicky, et al. 2004. Ornithomimosauria. In Weishampel, Dodson, and Osmolska (eds.), The Dinosauria Second Edition. University of California Press. 861 pages.

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