By Taylor McCoy

Tyrannosaurus rex. While the owner of that name may be long gone, it’s so powerful that it can invoke fear and respect even today. And it’s been doing so since 1905.

The story of T. rex as we know it began with a skeleton known as the holotype. In biology, a holotype is a particular specimen of an organism with which the scientific name of that organism is formally attached. Essentially, a holotype is an example that serves to anchor the defining features of that particular species. The holotype, or original T. rex, is known as CM 9380.

The bones of CM 9380 were first found in 1902 by world renowned paleontologist Barnum Brown. It would be another three years before the partial skeleton was fully unearthed.

At the time, the skeleton was held at the American Museum of Natural History of New York City. It was first known as AMNH 973. While being held at the American Museum of Natural History, curator and paleontologist Henry Fairfield Osborn named the beast Tyrannosaurus rex and wrote a description paper on it.

There were hopes of a dynamic display showcasing AMNH 973 fighting with another famous specimen, AMNH 5027. However, technical difficulties kept this from taking place.

Following the entry of the United States into World War II in 1941, the specimen of AMNH 973 was sold to the Carnegie Museum of Natural History in Pittsburgh. Here it was prepared further and put on display as CM 9380.

The skeleton still resides at the Carnegie to this day, displayed fighting another Tyrannosaurus over the carcass of a hadrosaur. Estimates place CM 9380 at roughly 11.9 meters long, or 39 feet. It’s weight has been estimated anywhere between 7.4–14.6 tons, with an average weight of around 9.1 tons. This makes CM 9380 one of the heaviest and most robust specimens of T. rex known.

The skeleton itself is far from complete, with the legs and hips being one of the better preserved aspects. The skeleton was originally displayed in a tripedal posture with the tail dragging behind it.

CM 9380 has since been updated to a more accurate pose with its body parallel to the ground.

While it may not be the most complete or the largest Tyrannosaurus ever found, CM 9380 is significant for what it represents. As the holotype, CM 9380 essentially sets the standard for T. rex. It introduced the world to the tyrant lizard king.

References

• Norell, M. A.; Gaffney, E. S.; Dingus, L. (1995). Discovering Dinosaurs in the American Museum of Natural History. New York: Knopf.
• Brown, B. (1915). “Tyrannosaurus, a Cretaceous carnivorous dinosaur, the largest flesh-eater that ever lived”. Scientific American.
• Makovicky, Peter J.; Allen, Vivian; Molnar, Julia; Bates, Karl T.; Hutchinson, John R. (12 October 2011). “A Computational Analysis of Limb and Body Dimensions in Tyrannosaurus rex with Implications for Locomotion, Ontogeny, and Growth”. PLOS One.
• Osborn, H.F. (1913). “Tyrannosaurus: restoration and model of the skeleton”. Bulletin of the American Museum of Natural History.

About the Author

Taylor McCoy is a paleontology enthusiast and volunteer at the Carnegie Museum of Natural History. He does fossil preperation at the Paleolab in the museum and field experience working in the Hell Creek Formation of Montana, where he worked alongside his wife. Taylor has written a few articles for I Know Dino and appeared in episode 316. You can follow him on Twitter @TM9380.