The Rise and Fall of the Dinosaurs: A New History of a Lost World: The Definitive Dinosaur Encyclopedia with Stunning Illustrations, Embark on a Prehistoric Quest!

by Steve Brusatte

the supercontinent we call Pangea, and the ocean we call Panthalassa.

So why don’t we see them in Portugal? It could be, of course, that we just haven’t found them yet. Absence of evidence is not always evidence of absence, as all good paleontologists must continually remind themselves.

Across much of the postcard-pretty landscape of northern Arizona and New Mexico are hoodoos, badlands, and canyons carved out of colorful red and purple rocks. These are the sandstones and mudstones of the Chinle Formation, a third-of-a-mile-thick rock sequence formed from the ancient sand dunes and oases of tropical Pangea during the last half of the Triassic, from about 225 to 200 million years ago.

Petrified Forest National Park, which should be on the itinerary of any dino-loving tourist visiting the southwestern states, has one of the best exposures of the Chinle Formation, full of thousands of enormous fossilized trees that were uprooted and buried in flash floods right around the time that dinosaurs were starting to settle in the area.

The culprit was carbon dioxide. Jessica’s measurements show that there were somewhere around 2,500 molecules of carbon dioxide per every million molecules of air in the tropical regions of Pangea back when the Hayden Quarry animals were alive. That’s more than six times the amount of carbon dioxide today. Let that sink in for a minute—just think about how quickly temperatures are rising now and how anxious we are about future climate change, even though there is much less carbon dioxide in today’s atmosphere. The high concentration of carbon dioxide in the Late Triassic started a chain reaction: huge fluctuations in temperature and precipitation, raging wildfires during parts of the year but humid spells in others. Stable plant communities had a difficult time establishing themselves.

A trade secret among paleontologists is that many of the fantastical numbers you see in books and museum exhibits—Brontosaurus weighed a hundred tons and was bigger than a plane!—are pretty much just made up. Educated guesses or, in some cases, barely that.

Based on their sizes and the nutritional quality of the most common Jurassic foodstuffs, it’s estimated that a big sauropod like Brontosaurus probably needed to eat around a hundred pounds of leaves, stems, and twigs every day, maybe more.

The sauropods weren’t competing for the same plants, but dividing the resources among themselves. The scientific term for this is niche partitioning—when coexisting species avoid competing with each other by behaving or feeding in slightly different ways.

Landmasses can move apart from each other by only a few centimeters each year, about the same pace that our fingernails grow.

(South America and Africa remained connected to each other long after links with North America, Asia, and Europe were severed.)

Lowell Dingus,

I'm highlighting this because it is a spectacular name for a human being. Or an even better name for a dog.

When today’s birds—and also T. rex—breathe in, oxygen-rich air courses through the lungs as you would expect. However, some of the inhaled air doesn’t go through the lungs right away but is shunted into a system of sacs connected to the lung. There it waits, until it is released when the animal exhales, passing through the lungs and delivering its oxygen-rich hit even as carbon dioxide waste is being expelled. Birds get twice the bang for the buck, a continuous supply of energy-sustaining oxygen. If you’ve ever wondered how some birds can fly at tens of thousands of feet, in rarefied air where we would have a hard time breathing (just ask anyone who has experienced the oxygen masks coming down midflight), their lungs are their secret weapon.

there is a straightforward measure that scientists use to roughly compare the intelligence of different animals. It’s called the encephalization quotient (EQ). It’s basically a measure of the relative size of the brain compared to the size of the body (because, after all, bigger animals have bigger brains simply because of their body size: elephants have bigger brains than we do but are not more intelligent). The largest tyrannosaurs like T. rex had an EQ in the range of 2.0 to 2.4. By comparison, our EQ is about 7.5, dolphins come in around 4.0 to 4.5, chimps at about 2.2 to 2.5, dogs and cats are in the 1.0 to 1.2 range, and mice and rats languish around 0.5. Based on these numbers, we can say that Rex was roughly as smart as a chimp and more intelligent than dogs and cats. That’s a whole lot smarter than the dinosaurs of stereotype.

There’s another scene in Jurassic Park where the freaked-out humans are told to stay still, because if they don’t move, then the T. rex can’t see them. Nonsense—because it could sense depth, a real Rex would have made an easy meal out of those sad, misinformed people.

Birds are dinosaurs. Yes, it can be hard to get your head around. I often get people who try to argue with me: sure, birds might have evolved from dinosaurs, they say, but they are so different from T. rex, Brontosaurus, and the other familiar dinosaurs that we shouldn’t classify them in the same group. They’re small, they have feathers, they can fly—we shouldn’t call them dinosaurs. On the face of it, that may seem like a reasonable argument. But I always have a quick retort up my sleeve. Bats look and behave a whole lot differently than mice or foxes or elephants, but nobody would argue that they’re not mammals. No, bats are just a weird type of mammal that evolved wings and developed the ability to fly. Birds are just a weird group of dinosaurs that did the same thing.

We’re so used to saying that dinosaurs are extinct, but in reality, over ten thousand species of dinosaurs remain, as integral parts of modern ecosystems, sometimes as our food and our pets, and in the case of seagulls, sometimes as pests.

The more fossils we find—particularly in Liaoning—the more complex the story gets. The early development of flight appears to have been chaotic. There was no orderly progression, no long evolutionary march in which one subgroup of dinosaurs was refined into ever better aeronauts. Instead, evolution had produced a general type of dinosaur—small, feathered, winged, fast-growing, efficient-breathing—that had all of the attributes needed to start playing around in the air. There seems to have been a zone on the dinosaur family tree where this type of animal had free reign to experiment. Flight probably evolved many times in parallel, as different species of these dinosaurs—with their different airfoil and feather arrangements—found themselves generating lift from their wings as they leaped from the ground, scurried up trees, or jumped between branches.

WHAT HAPPENED ON that day—when the Cretaceous ended with a bang and the dinosaurs’ death warrant was signed—was a catastrophe of unimaginable scale that, thankfully, humankind has never experienced. A comet or an asteroid—we aren’t sure which—collided with the Earth, hitting what is now the Yucatán Peninsula of Mexico. It was about six miles (ten kilometers) wide, or about the size of Mount Everest. It was probably moving at a speed of around 67,000 miles per hour (108,000 kilometers per hour), more than a hundred times faster than a jet airliner. When it slammed into our planet, it hit with the force of over 100 trillion tons of TNT, somewhere in the vicinity of a billion nuclear bombs’ worth of energy. It plowed some twenty-five miles (forty kilometers) through the crust and into the mantle, leaving a crater that was over 100 miles (160 kilometers) wide. The impact made an atom bomb look like a Fourth of July cherry bomb. It was a bad time to be alive.

When there is sudden global environmental and climate change, what lives and what dies? It’s case studies in the history of life—recorded by fossils, like the end-Cretaceous extinction—that provide critical insight. The first thing we have to realize is that, although some species did survive the immediate hellfire of the impact and the longer-term climate upheaval, most did not. It’s estimated that some 70 percent of species went extinct. That includes a whole lot of amphibians and reptiles and probably the majority of mammals and birds, so it’s not simply “dinosaurs died, mammals and birds survived,” the line often parroted in textbooks and television documentaries. If not for a few good genes or a few strokes of good luck, our mammalian ancestors might have gone the way of the dinosaurs, and I wouldn’t be here typing this book.

While dinosaurs bested their early crocodile competitors, sailed through the end-Triassic extinction, and then grew to colossal sizes and spread throughout the land, mammals remained in the shadows. They became adept at surviving in anonymity, learning how to eat different foods, hide in burrows, and move around undetected, some even figuring out how to glide through the canopy and others how to swim. All the while, they remained small. No mammal living with dinosaurs got bigger than a badger. They were bit players in the Mesozoic drama.

We humans now wear the crown that once belonged to the dinosaurs. We are confident of our place in nature, even as our actions are rapidly changing the planet around us. It leaves me uneasy, and one thought lingers in my mind as I walk through the harsh New Mexican desert, seeing the bones of dinosaurs give way so suddenly to fossils of Torrejonia and other mammals. If it could happen to the dinosaurs, could it also happen to us?