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

Everything I describe above is what we call a body fossil, an actual part of a plant or animal that turns into stone. But there is another type: a trace fossil, which records the presence or behavior of an organism or preserves something that an organism produced. The best example is a footprint; others are burrows, bite marks, coprolites (fossilized dung), and eggs and nests.

He developed a particular talent for finding a type that many paleontologists ignore: trace fossils. Footprints, hand impressions, tail drags: the marks dinosaurs and other animals left when they moved across mud or sand, going about their daily business of hunting, hiding, mating, socializing, feeding, and loitering.

Early in the Triassic, archosaurs split into two major clans: the avemetatarsalians, which led to dinosauromorphs and dinosaurs, and the pseudosuchians, which gave rise to crocodiles. During the dizzying splurge of postextinction evolution, the pseudosuchian tribe also produced a number of other subgroups that diversified in the Triassic but then went extinct.

Ecosystems on land and in the oceans couldn’t cope with such rapid change. The much hotter temperatures made it impossible for many plants to grow, and indeed upwards of 95 percent of them went extinct.

Putting it all together, that’s how you can build a supergiant dinosaur. If sauropods had lacked any one of these features—the long neck, the fast growth rates, the efficient lung, the system of skeleton-lightening and body-cooling air sacs—then they probably would not have been capable of becoming such behemoths.

Argentinosaurus, which at more than a hundred feet (thirty meters) long and fifty tons in mass was the largest animal known to have ever lived on land.

Iguanodon

Tyrannosaurus rex—a beautiful combination of Greek and Latin that means “tyrant lizard king”—and

Maybe you’ve heard the rumor that T. rex liked its meat dead and rotten, that Rex was a scavenger, a seven-ton carcass collector too slow, too stupid, or too big to hunt for its own fresh food. This accusation seems to make the rounds every few years, one of those stories that science reporters can’t get enough of. Don’t believe it.

Not, as it turns out, with exceptional speed. T. rex was a special dinosaur in many ways, but one thing it could not do is move very fast. There’s a famous scene in Jurassic Park where the bloodthirsty T. rex, convulsed by its insatiable appetite for human flesh, chases down a jeep driving at highway speeds. Don’t believe the movie magic—the real T. rex likely would have been left in the dust once the jeep got up to third gear. It’s not that Rex was a plodding slouch that waddled through the forest. Far from it—T. rex was agile and energetic, and it moved with purpose, its head and tail balancing each other as it tiptoed through the trees, stalking its prey. But its maximum speed was probably in the ballpark of ten to twenty-five miles per hour. That’s faster than we can run, but it’s not as quick as a racehorse or, certainly, a car on the open road.

Vision, too: the huge eyeballs of T. rex faced partially to the side and partially to the front, meaning that they were capable of binocular vision. The King could see in three dimensions and perceive depth, just like us. 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.

None of these reptiles were dinosaurs—even though they are often mistaken for dinosaurs in popular books and movies, they were merely distant reptilian cousins. For whatever reason—and we don’t yet know the answer—no dinosaurs were able to do what whales did: start on the land, change their bodies into swimming machines, and make a living in the water.

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.

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.