Naming Day Celebrates 114 Years of Tyrannosaurus rex

It’s Saurian Saturday, but we’re going to keep our eye squarely on our namesake subject. On this day in 1905, Henry Fairfield Osborn’s article “Tyrannosaurus and Other Cretaceous Carnivorous Dinosaurs” was published in Journal of the American Museum of Natural History, volume 21. In the seven page paper, Osborn described several dinosaurs. But he led with a description of a dinosaur discovered in 1902 by Barnum Brown in Montana. He concluded the paragraph by stating “I propose to make this animal the type of the new genus Tyrannosaurus, in reference to its size, which greatly exceeds that of any carnivorous land animal hitherto described.”

Osborn went on to describe what he named Tyrannosaurus rex, a name he chose to accentuate the large size of the dinosaur in relation to other land animals. “When placed together, as provisionally outlined by Dr. W. D. Matthew, the enormous proportions of this animal become very evident as compared with the skeleton of a man, the total length being estimated at thirty-nine feet, the height of the skull above the ground at nineteen feet.”

The type specimen for Tyrannosaurus rex is now housed at the Carnegie Museum of Natural History in Pittsburgh, PA.

The type specimen for Tyrannosaurus rex is now housed at the Carnegie Museum of Natural History in Pittsburgh, PA.

In the same paper, Osborn described five dinosaurs, including Dryptosaurus and Deinodon. Then, after two pages of description and measurements of T. rex, he goes on to describe a jaw found by Brown in Wyoming in 1900. This order - whether intentional or by circumstance - would have a profound effect on the retention of T. rex as a name. In 1906, Osborn would clarify that this specimen, which he gave the name Dynamosaurus imperiosus, was actually the same species as T. rex. And by a simple order of the words on the pages, D. imperiosus would fade into obscurity, while T. rex would, well, do I really need to describe what happened?

CM 9380 - the holotype Tyrannosaurus rex (left) - along with a cast of Museum of the Rockies’ MOR 980 “Peck’s rex” (right) and a fallen hadrosaur.

CM 9380 - the holotype Tyrannosaurus rex (left) - along with a cast of Museum of the Rockies’ MOR 980 “Peck’s rex” (right) and a fallen hadrosaur.

In addition to T. rex and Dynamosaurus, Osborn’s paper also introduced the world to Albertosaurus, using the name to differentiate two skulls found in Alberta in 1886 and previously described to Dryptosaurus. And that’s a story for a different time.

Osborn’s paper also contained illustrations of the jaw of Dynamosaurus, and the expected full skeleton of T.rex, including an incorrectly shaped skull. Much to the pattern of paleontology of the time, Osborn mentions that the suppositions are because “The jaws and skull are not as yet prepared for description, so that comparison of these parts cannot be made at present with Dynamosaurus or Albertosaurus.” No doubt that led to the clarification the following year. The complete text of Osborn’s 1905 paper are archived by the American Museum of Natural History, and can be found by following this link.