How Was Tyrannosaurus Rex Discovered?

Tyrannosaurus Sue at the Field Museum of Natural History (Fritz Geller-Grimm).

Easily the most famous dinosaur that ever lived, Tyrannosaurus Rex is a case study in how much we know, and how much we don’t know, about how dinosaurs behaved millions of years ago. For example, while we have a pretty good idea what T. Rex looked like, we’re still not sure whether it actively hunted its food, whether it was warm- or cold-blooded (or something in between), or even whether it could run faster than a little old lady on a three-speed bike.

Tyrannosaurus Rex: The Early Years

Some of the first, fragmentary fossils of Tyrannosaurus Rex were discovered by the famous paleontologist Edward Drinker Cope (with Othniel. C. Marsh, one of the participants in the notorious 19th-century Bone Wars) in South Dakota in 1892. Drinker promptly named his find Manospondylus gigax, which translates roughly as “giant thin vertebra”—and who knows how history might have changed if that colorless name had stuck. (In retrospect, because they were only classified years after the event, various T. Rex fragments were discovered before 1892: scattered teeth in Colorado, in 1874, and skull fragments in Wyoming around 1890.)

Fortunately, a succession of more complete fossil discoveries in Wyoming shortly after the turn of the century (by Barnum Brown, the assistant curator of the American Museum of Natural History who was named after the circus impresario P.T.

Barnum) spared the king of dinosaurs from being saddled with the plebeian name Manospondylus. In 1905, the patrician president of Brown's museum, Henry Fairfield Osborn, officially dubbed this dinosaur Tyrannosaurus Rex, Greek for “tyrant lizard king.”

The Tyrannosaur Family Grows

Technically, Tyrannosaurus Rex is a species (and the only known species) of the genus Tyrannosaurus.

However, paleontologists have since discovered the fossils of numerous related genera, from various parts of the world, which all fall under the general category of tyrannosaurs. Additional tyrannosaur discoveries from North America--including Gorgosaurus, Albertosaurus and Appalachiosaurus--proved different enough from T. Rex to merit being assigned to their own genera, and tyrannosaurs have since been discovered across the expanse of Eurasia, including a few extremely tiny, primitive members of the breed (such as Dilong) from China.

A brief word about another genus that's often included in this list of tyrannosaurs, Nanotyrannus (literally, “tiny tyrant.”) It’s still a matter of some dispute whether this dinosaur, which was identified on the basis of a single fossilized skull discovered in the 1940’s, represents a genuinely new, pint-sized species of tyrannosaur or was simply an unfortunate T. Rex juvenile who happened to die young. It's also possible that Nanotyrannus wasn't a true tyrannosaur at all, but a modestly proportioned theropod of the raptor family.

A Girl (or Boy) Tyrannosaurus Rex Named Sue

The most spectacular Tyrannosaurus Rex discovery to date was made by the (then) amateur fossil hunter Sue Hendrickson, who unearthed a near-complete Tyrannosaurus Rex skeleton in South Dakota in 1990.

Named “Sue” in Hendrickson’s honor, this individual apparently perished at the age of around 30 from a bite to the head (which counts as natural causes during the Cretaceous period), making it the oldest T. Rex yet identified. (By the way, don’t let the name fool you—it’s unknown whether Dinosaur Sue was male or female, though paleontologists now believe that female tyrannosaurs tended to be bigger than males.)

Proving that no good T. Rex deed goes unpunished, Hendrickson spent the next few years after her discovery immersed in legal proceedings pertaining to Sue’s provenance and ownership--kind of like the custody battle in Kramer vs. Kramer, but with a very, very big child at stake. A court finally ruled that Sue’s bones belonged to the person who owned the piece of land where she was discovered, and in 1997 the remains were auctioned off to Chicago’s Field Museum of Natural History for $8 million, at the time a record amount of cash for a single dinosaur.

So Many Tyrannosaurus Rex Questions…

In a way, the popularity of Tyrannosaurus Rex has been both a blessing and a curse for paleontologists. On the plus side, any scientist who makes a major discovery about T. Rex behavior or physiology is sure to land herself front-page headlines around the world. On the minus side, people don’t like it when their idols are tampered with, especially if a supposedly fearsome, unstoppable dinosaur is shown to be, well, kind of a wimp, or even (heavens forfend) covered with feathers. (There is now some indirect evidence, extrapolated from feathered tyrannosaurs like Yutyrannus, that T. Rex was feathered during at least some part of its life cycle, possibly when it was a hatchling or juvenile.)

For example, nothing gets a Tyrannosaurus Rex fan’s blood boiling like the theory that T. Rex scavenged for its food rather than actively hunting it down (the evidence today points to this dinosaur indulging in both behaviors, making Rex an opportunistic predator; see Was T. Rex a Hunter or Scavenger?)), or that this dinosaur was slower than a New York City bus during rush hour, rather than the speedy menace of the Jurassic Park movies (see How Fast Could Dinosaurs Run?). No matter what the experts say, though, you can be sure that Hollywood will go on portraying Tyrannosaurus Rex the old-fashioned way--as the perpetually grumpy, hungry, fleet-footed king of the dinosaurs.