Scientists Say Dinosaurs Were Likely Different From What Most of Us Picture

UC Berkeley paleontologist Jack Tseng explains how new discoveries challenge our long-held beliefs about the world of paleontology.

For a long time, paleontologists thought that the famous, long-extinct apex predator, the Tyrannosaurus rex, may have chased its prey at high speeds. Children’s books and movies often showed the dinosaur sprinting at a terrifying pace; you might remember scenes from the 1993 film Jurassic Park in which a massive T. rex chases characters who are escaping in a Jeep that they’re driving as fast as they can.

But in the past few decades, paleontologists have found that this wasn’t exactly accurate — and it’s one of a number of ideas we’ve long held about these ancient creatures that are being reshaped by modern science. 

“After really sort of ground truthing, figuring out how much bone and tissue needs to be on the animal to reach a particular speed with enough power, people realized Tyrannosaurus probably didn’t run more than 20, 25 miles per hour,” says Jack Tseng, a UC Berkeley vertebrate paleontologist and functional morphologist. 

This article was adapted from a Berkeley Voices podcast episode. Listen to the original episode here.

Tseng, who studies the relationship between an organism’s physical structure and its function in the environment, says paleontologists figured out that T. rexes were slower than once believed by studying living bipedal birds, like chickens and ostriches. Because paleontologists can’t study the soft tissue of extinct animals, like their muscles or their digestive physiology, they rely instead on living animals, like birds, crocodiles and mammals, to provide clues.

In the past few decades, with the advance of imaging technology and the ability to share research across the globe, paleontologists have made leaps in their knowledge of prehistoric animals. It’s changing the popular images we hold about what dinosaurs looked like and how they lived. 

And those findings, Tseng says, also hold powerful lessons for what it means to imagine our earth millions of years in the future.

Studying living animals to understand ancient ones

In the Department of Integrative Biology, associate professor Tseng teaches a handful of classes related to paleontology, including Life During the Age of Dinosaurs. 

In one of his lectures about sauropods — the huge, plant-eating dinosaurs with super long necks — Tseng discusses a working recent hypothesis about how these gigantic animals, the biggest to ever walk the earth, were able to take in adequate oxygen through their necks, which could reach lengths of up to 50 feet. 

Researchers started by looking at living animals that move at extreme speeds and needed an elevated air supply, like peregrine falcons, which reach speeds of more than 200 miles per hour when diving to capture prey, or cheetahs, which can accelerate from 0 to 60 miles per hour in just three seconds. 

They found that many birds — the only living dinosaurs today — have hollow bones, not just to make them lighter for flight, but also around their lungs, allowing them to expand their aerobic capacity more than they could otherwise. Sauropods had a similar hollowness in the bones of their vertebral columns, which paleontologists now believe acted as pseudo lung systems, helping them get enough oxygen down their necks all the way to their lungs. 

“We can really start to conclude some seemingly impossible inferences about extinct animals just by understanding how living animals work,” says Tseng, “creating this bridge from biology to paleontology.”

Our ever-evolving ideas of dinosaurs

Tseng’s office is in the campus’s Valley Life Sciences Building, which houses the university’s Museum of Paleontology. It holds one of the largest paleontological collections of any university museum in the world. 

While most of the collection is open only for research, there is a huge replica of a T. rex nicknamed Osborn in the lobby right when visitors walk in. It’s one of the most complete T. rex skeletons ever reconstructed. The specimen was originally discovered in the Hell Creek formation, a rock formation in Montana famous for producing a large number of dinosaur fossils. 

If you look at books from 50 years ago, they postured dinosaurs very differently from the way we do it today.

In addition to studying living animals in order to understand how extinct animals functioned, Tseng says on-the-ground, field research-based discoveries have fundamentally changed how we think about the appearance of dinosaurs. 

In a lot of books, most dinosaurs look kind of like giant, dull-colored lizards. They’re often scaly, in muted shades of brownish green. But in the past several decades, says Tseng, paleontologists around the world have uncovered dinosaur bones with feathers around them, representing species they didn’t realize were feathered before, including tyrannosaurs, the group of predatory dinosaurs that the T. rex belonged to.

“In some paleoartistic reconstructions, you will see furry T. rex,” says Tseng. “We think it’s likely that at least at one point in their lives, they probably had bodies that were partially or completely covered in feathers. … Maybe they were more like modern birds, which are among the most extravagant animals.” 

To complicate our image of the T. rex even more, some researchers posit that T. rexes were actually scavengers instead of active hunters, based in part on the preservation of tooth bite and scratch marks on fossils of their potential prey. Tseng has studied the bite mechanics of Jane, a juvenile Tyrannosaurus rex, to learn more about the forces involved in biting prey. 

“Modern scavengers, as we understand them, tend to go for carcasses, which are either decomposing or hardened. It involves different forces and sharpness of the teeth vs. active predators going after moving prey and potentially having access to fresh tissues.

“If they didn’t hunt and were scavengers, it would blow everyone’s mind,” I say.  

“Yeah,” he admits. “That would be very disappointing for a lot of kids.” 

Unlike other sciences, paleontology and its evolving knowledge is documented at length in the popular record, especially in children’s books. 

“If you look at books from 50 years ago, they postured dinosaurs very differently from the way we do it today,” Tseng says. “The dinosaurs are still the same dinosaurs, but the way we understand them as living animals has changed dramatically over the past several decades. It’s a lovely way to sort of see how this science has progressed.”

Fossils hold clues about our future

Tseng says there are increasingly practical aspects of paleontology that can be applied to what we’re facing as a species today with climate change. 

In paleontology, he says, everything has already happened. Dinosaurs and other animals and many plants went extinct, and it’s recorded in rocks for us to study. We know the outcomes of evolutionary history. 

Bu we don’t necessarily know how they got to that point. And fossils — of vertebrates, like dinosaurs, fish and mammals, but also especially of plants and invertebrates, like mollusks — hold a lot of these clues.

“The questions we ask of them have to do with how different species sometimes survive when others go extinct,” he says. “How they adapt to environmental changes — warming and cooling cycles, habitat disturbances or dispersals of species from one continent to another. 

“In a way, paleontology is sort of pre-adapted to plug in to understanding the future of Earth because we have billions of years of the fossil record to learn from.”

Tseng says he can imagine a figure where, if the human species goes extinct, paleontology will live on, perhaps practiced by another species who can look back and see our fossil record — “a tiny slice of time in which our species lived on this earth,” says Tseng. 

“It makes you wonder what they are going to see when all is said and done. Are they going to see a species that drove ourselves to extinction? Are they going to see one that actually managed somehow to coexist with other life on Earth, maybe even improving things and creating new biodiversity? 

“Even though, as far as we know, the human species is the first one to do science and record history on this planet, we might not be the last.”