Gallimimus was a theropod dinosaur that lived in what is now Mongolia during the late Cretaceous, about 70 million years ago. Adults could grow to about twenty feet long from beak to tail. The genus name translates to "chicken mimic" because the neck bones were particularly similar to those of modern chickens and other galliform birds, like pheasants and turkeys. The species name is in reference to a bulla, a locket-like piece of jewelry worn by young boys in ancient Rome. The back part of Gallimimus' skull reminded some scientists of the shape of these pieces of jewelry. When alive, Gallimimus shared its environment with other dinosaurs, including Therizinosaurus, Tarbosaurus, and fellow ornithomimid, Deinocheirus.
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| Life reconstruction of Gallimimus in watercolors by Christopher DiPiazza |
Gallimimus was a member of the family of theropod dinosaurs, called ornithomimidae. Ornithomimids all had long arms, long necks, and proportionally small heads. Most of them also had long legs and a sleek build, suggesting they could run fast. Struthiomimus, which lived what is now North America, is another famous member of this family. (Deinocheirus, the largest known ornithomimid, was an exception to the sleek part of the description.) Gallimimus was probably a very fast runner when it was alive, using its long powerful legs to take huge strides and its proportionally long tail to keep balance as it ran. Like birds today, Gallimimus had hollow chambers in its bones, which would have been filled with air sacs in life. These sort of adaptation allows the dinosaur to intake more oxygen into its body than it would if it was only relying on its lungs. Gallimimus also probably had a one-way breathing system, where fresh air cycled through its body in one direction, instead of in and out like the respiratory systems of mammals. Having a more efficient way to oxygenate the body means that Gallimimus could likely run faster for longer periods of time before it got tired. Being able to outrun predators, like Tarbosaurus, was probably Gallimimus' primary defense.
Gallimimus is known from adult and baby individuals. What is interesting is that the baby Gallimimus, have different skull shapes than the adults, with a much shorter snouts and proportionally larger eyes. This is consistent with many baby animals today that are cared for by their parents. Baby crocodilians and baby birds being the two best examples to compare here.
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| Baby Gallimimus skeleton on display in Cosmo Caixa Science Museum in Barcelona. Photo credit Edward Sola. |
As an adult, Gallimimus had a very long, toothless snout which was tipped with a beak. The shape of Gallimimus' beak is more broad than those of many other ornithomimids, like Struthiomimus. The underside of the beak possessed a series of thin tube-shaped structures, which some paleontologists suggest were adaptations for filter feeding water plants and small aquatic animals, since modern ducks and geese have similar structures in their beaks for feeding this way. Other paleontologists think the structures in Gallimimus' beak were more adapted for cutting through tough vegetation on land, instead. In addition to plants, Gallimimus, may very well have also eaten meat in some forms, like insects and other small animals it was able to snap up. Gallimimus also had large eye sockets, suggesting it had good vision, which it probably used to help pick out food and look out for potential predators.
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| Adult Gallimimus skeleton on display at the Natural History Museum in London. Photo credit" Drow male. |
The arms of Gallimimus were proportionally long, but its fingers were short compared to the fingers of other known ornithomimids. Its arms also don't show signs of being as strong as those of other ornithomimids either. This means that unlike many of its relatives, which probably relied on their arms and hands for manipulating food more, Gallimimus may have relied on its beak and neck for foraging more.
That is all for this week! As always feel free to comment below!
References
Hurum, J. 2001. Lower jaw of Gallimimus bullatus. pp. 34–41. In: Mesozoic Vertebrate Life. Ed.s Tanke, D. H., Carpenter, K., Skrepnick, M. W. Indiana University Press.
Makovicky, P. J.; Kobayashi, Y.; Currie, P. J. (2004). "Ornithomimosauria". In Weishampel, D. B.; Dodson, P.; Osmolska, H. The Dinosauria (2 ed.). Berkeley: University of California Press. pp. 137–150.
Nicholls, E. L.; Russell, A. P. (1985). "Structure and function of the pectoral girdle and forelimb of Struthiomimus altus (Theropoda: Ornithomimidae)". Palaeontology. 28 (4): 64 –677.
Osmolska, H.; Roniewicz, E.; Barsbold, R. (1972). "A new dinosaur, Gallimimus bullatus n. gen., n. sp. (Ornithomimidae) from the Upper Cretaceous of Mongolia" (PDF). Palaeontologia Polonica. 27: 103–143.
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