It’s been over 30 years since the discovery of the Nation’s Tyrannosaurus rex. The fossil, now on display in the “David H. Koch Hall of Fossils - Deep Time” at the Smithsonian’s National Museum of Natural History has been around for at least 66 million years. But much of what scientists know about it and its family members has changed over the decades.
"There have been huge discoveries over the last three decades. We didn’t have a great understanding of these animals, but now, for any topic we might want to explore in dinosaurs, there’s somebody who has already thought about studying it in a T. rex,” said Matthew Carrano, paleontologist and curator of Dinosauria at the museum.
Here are some key discoveries paleontologists have made about the “tyrant lizard king” over the last 30 years.
It had a short reign
Back when the first T. rex skeleton was found, scientists didn’t know its age very precisely. They didn’t have the necessary technology to date fossil rocks so old. And with so few specimens to study, it was impossible to figure out how long the species existed before it went extinct.
“They just didn’t have a very good way of specifying its age,” said Carrano.
Now, researchers use technology like radiometric dating to analyze the rock beds surrounding dinosaur fossils to find out when different dinosaur species were alive.
“This is usually done in parallel with geologists who are working to more broadly understanding the ages of different rocks on Earth,” said Carrano.
Since 1988 when the Nation’s T. rex was discovered, scientists have revealed that Tyrannosaurus rex roamed Western North America around 68 to 66 million years ago, or at the tail end of the Cretaceous. The species survived no more than 2 million years — and perhaps even less — a fairly short time geologically speaking.
It belonged to one big, global family
Three decades ago, scientists believed T. rex’s taxonomic family, Tyrannosauridae, was relatively small. They were only certain that it had a few relatives in Canada and Central and East Asia, but they suspected other related species existed too.
“These were a group of fossils that looked pretty similar, so we had a vague sense that they might be related to T. rex on the tree of life,” said Carrano. “But now there are many more.”
In fact, Tyrannosaurus rex was part of a very big group of dinosaurs. One early relative was Proceratosaurus bradleyi, a small form that lived in what is now Europe 100 million years before T. rex evolved. Two larger species, called Appalachiosaurus montgomeriensis and Dryptosaurus aquilunguis, were found in present-day southern United States and New Jersey respectively.
“It’s become clear in Eastern North America that there were actually two tyrannosaur species,” said Carrano. “But because Eastern and Western North America were separated by an ocean at the time, these tyrannosaurs never encountered the giant Tyrannosaurus rex of the West.”
It could have had feathers
From the 1960s onwards, scientists suspected there was an evolutionary link between ancient dinosaurs and modern birds. Today, even more evidence suggest birds are descendants of predatory dinosaurs. For example, a new study in the 2000s on fossilized members of the tyrannosaur family found that two of T.rex’s Asian relatives, the tiny Dilong paradoxus and the much larger Yutyrannus huali, had feathers.
“This was a really big deal and it allowed paleobiologists to start answering new questions about what these animals looked like,” said Carrano.
The finding revolutionized how researchers visualized all tyrannosaurs, leading them to wonder whether T. rex. also may have had feathers. But recent skin impressions taken from T. rex and its closest relatives have shown only scale patterns, so the feather debate continues for now.
Its fossilized bones may hold traces of blood
Fossils are usually thought of as the mineralized skeletons of organisms with no soft tissue. But for dinosaur fossils, that may not always be true.
During the 1990s and 2000s, a paleontologist named Mary Schweitzer began to explore whether there was hemoglobin, a protein found in blood cells, in Tyrannosaurus rex fossils.
“These discoveries overlap with a period in paleontology where lots of new techniques and possibilities were coming online, so to speak,” said Carrano. “So, some of this knowledge comes from new ways of thinking about how to look at the past.”
For Schweitzer, this meant dissolving T.rex fossil specimens in acid to distill any remaining soft tissue samples. After finding traces of hemoglobin, she published her first paper in 1997 to much controversy. The unorthodox process had destroyed ancient fossil material and no one was able to replicate her dinosaur protein analysis experiments.
“This famous study and the fact that people debate it is less relevant than the fact that it has encouraged people to look for things like this,” said Carrano. “Beforehand, you’d never in a million years even think you’d find blood vessels in a dinosaur bone.”
It’s now a model organism for research
Although its original discovery was nearly 100 years ago, scientific interest in T. rex hasn’t dimmed. Paleontologists continue to use the species to find out more about tyrannosaurs, and dinosaurs in general.
“A lot of experiments for determining shape, size, speed and weight for dinosaurs were refined using Tyrannosaurus rex as a model,” said Carrano.
While the Nation’s T. rex teaches visitors at the National Museum of Natural History about past life on Earth, its relatives keep inspiring researchers to examine ancient dinosaurs in new ways.
“Studying Tyrannosaurus rex has historically had a ripple effect for changing how we ask and answer future paleontological questions,” said Carrano.
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