For most, dinosaurs are little more than useless trivia fodder leftover from elementary school days that have no bearing on modern life. They were dumb, slimy, vicious animals of gargantuan proportions that couldn’t figure out how to survive. But the cliches we’ve garnered from grade-school teachers and creature-feature monster movies are totally off-base. The study of dinosaurs is evolving rapidly as more dinosaurs are being discovered than ever before—a new species of dinosaur once a week, everywhere from South American deserts to the North American tundra to East Asian rice fields.

The surge of new discoveries is reshaping the way scientists think of these beasts, and new technologies are giving us fresh insight into what life was like then and how that world has shaped the world we live in today. The rise and fall of dinosaurs is a legacy that lives with us today—even 66 million years after they went extinct. During their 150 million-year rise to dominance, dinosaurs survived and adapted to dramatic changes, a process that produced a complex cast of zoological characters—including 10,000 species of birds that we have today. These are all modern-day dinosaurs, and it turns out that their primeval forbears had feathers, too—including the infamous Tyrannosaurus rex. These are just some of the many discoveries that the paladin of paleontology Steve Brusatte draws to our attention in his critically acclaimed book, The Rise and Fall of Dinosaurs.

Picture a world with no mice, no birds, and no mosquitoes. There are no dinosaurs in sight, but there are giant salamander-like creatures the size of dogs, portly hog-like creatures called dicynodonts that ripped up roots with their tusks, and gorgonopsians, ferocious apex predators that looked like a cross between a bear and a saber-tooth tiger. These were the curious characters who ruled the world before dinosaurs were on the scene.

This was 252 million years ago, and earth was a different place. It was right at the very end of the Paleozoic Era and right before the Mesozoic Era, the era when dinosaurs came to rule the planet. Back then, the continents we are familiar with today were still clumped together in one massive heap of terra firma called Pangea. One supercontinent meant there was also only one giant, unbroken ocean known as Panthalassa. (Geography exams would have been a breeze back then!) 

Rule by saber-tooth bears and giant salamanders ended when magma roiling in the Earth’s mantle (beneath the outer crust) began shooting up to the surface. These weren’t the volcanoes we’re familiar with, where a Vesuvius or Saint Helens boils over every few decades. These volcanoes (more like giant, miles-long cracks in the ground than the mountains we imagine) launched lava and ash consistently for millennia in modern-day Siberia. Picture a region the size of Western Europe, singed and buried under layer after layer of lava.

Worse than millennia of napalm-like spray were the poisonous gas, heat, and dust that encircled the globe. The plants that did survive the molten onslaught were not able to photosynthesize because of the ash and debris that completely obscured the sun. The staggering levels of carbon dioxide the volcanoes emitted dramatically raised the planet’s temperatures and made the ocean too acidic for most sea creatures to survive.

All this led to the single-most destructive mass extinction in Earth’s 4.5 billion-year history. (There have been five mass extinctions altogether.) About 90 percent of all species succumbed to the destruction.

After that, life improved around Planet Earth. The planet healed and stabilized over the course of five million years. Out of the ashes of this disaster came what we now call dinosaurs, but that didn’t happen all at once.

Dinosaurs lived within a timeframe called the Mesozoic Era, which can be divided into three main periods: the Triassic, the Jurassic, and the Cretaceous. Let’s set the scene for the beginning of the Triassic, when dinosaurs were far from a dominant force. What was that world like?

The climate would have been dramatically different in the beginning of the Triassic period. It would have been far hotter and far more humid—enough to make South Florida feel like the tundra. This was partly because there was far more carbon dioxide in the air. Another reason is the lack of polar ice caps in the Arctic and Antarctic. A giant ocean without interspersed continents like in the modern world meant that currents flowed across the globe without interruption. So these currents would pick up water from the sweltering equatorial regions and move unhindered toward the poles. With temperatures too warm for polar ice caps to form, the poles reached temperatures comparable to San Franciscan summers and dropped to just below freezing in the winters. If the weather was this temperate at the poles, imagine how hot it would have been at the equator! It would have been a tropical inferno. And all the warm air from the lower latitudes would have been a recipe for not just monsoons—but super-monsoons. Suffice it to say, Earth was not a hospitable place.

It can’t be stressed enough that dinosaurs were unlikely candidates for taking over the world. Notwithstanding the hostile climates and volatile weather, dinosaurs didn’t come out swinging the moment the dust and volcanic ash settled at the beginning of the Triassic. In fact, dinosaurs weren’t around at all yet. The closest resemblance to dinosaurs at that time were “dinosauromorphs” that started showing up about 240 million years ago. These proto-dinos looked like carnivorous, cat-sized lizards running around on their hind legs—not exactly ruler-of-the-world material. If these dinosauromorphs lingered too long by the shallows of lakes and ponds, they’d be readily snapped up by salamanders the size of humans, with rows of scalpel-sharp teeth or any number of superior predators.

Even by the end of the late Triassic, dinosaurs were still scrappers that had not managed to claw themselves beyond a low- to mid-tier existence. There were no behemoths on the scene, like Brachiosauruses or T. rexes. They were not yet a force to be reckoned with, but were peripheral in the world of Pangea. If you had to place a bet on which group would gain the upper hand, the proto-crocodile groups looked like  stronger competitors. They were far bigger and tougher than the dinosaurs during the 30 million years that the dinosaurs and proto-crocodile groups overlapped.

What changed for dinosaurs? How did a rag-tag group of small and mid-sized animals go on to seize the Lost World’s crown when there were so many stronger contenders for the title? From what paleontologists can piece together through fossil records, it had a lot to do with the harrowing, volcano-inspired continental drift. The volcanic activity caused Pangea to begin breaking apart. It’s hard to imagine a world in which Morocco and New York City border each other, but at the end of the Triassic and beginning of the Jurassic, they were nestled next to each other.

If you view Newark from the New York City side, you see cliffs hundreds of feet tall known as the Palisades. These cliffs are a remnant of the volcanic inferno that raged at the tail-end of the Triassic period, and very close to the Palisades in the Newark Basin is a veritable dinosaur graveyard.

Before that volcanic activity, dinosaurs comprised only 20 percent of the fossil record. After the volcanic inferno that jump-started the continental drift, dinosaurs made up over 50 percent of the fossil record—and then more! Apparently, the volcanic activity and Pangea getting ripped apart was the chaos that the dinosaurs needed to upend the primordial pecking order.

Scientists wish they understood better exactly how this great reversal happened, but fossils from before and after the cataclysm tell us that the impossible happened: Apex predators that dominated dinosaurs began dying out—often very suddenly, while dinosaurs became more prevalent and dominant, even under harrowing conditions. They grew larger and wildly diverse, and they did so quickly—at least in evolutionary terms. Through analysis of limb-bone thickness and 3-D software that can calculate body mass based on the size of samples, scientists have been able to accurately estimate the weight of these dinosaurs and how dramatically that weight and size increased over the course of the Jurassic and Cretaceous periods.

Sauropods are a prime example of dinosaurs’ staggering growth. Sauropods are the iconic family of pot-bellied, long-necked dinosaurs like Brontosauruses and Brachiosauruses. Their ancestors in the late Triassic maxed out at two or three tons—the same size as a giraffe, maybe slightly bigger. Once Pangea began coming unglued, they got significantly bigger—around 20 tons. By the end of the Jurassic when Brachiosauruses and Brontosauruses were on the scene, 30 tons was not out of the question. By the Cretaceous period (after the Jurassic), some sauropods (fittingly called “titanosaurs”) could weigh in at over 50 tons. Compare that to today’s adult elephants that average a “mere” five to six tons, and you get a sense of these dinosaurs’ enormity.

No history of the dinosaurs would be complete without tipping our hats to the King of the Beasts itself: the Tyrannosaurus rex, the largest land predator in the planet’s 4.5 billion-year history.

An adult T. rex could grow up to 42 feet long (longer than a city bus!) and weighed between seven and eight tons. Even the closest rivals, like the Allosaurus or the Giganotosaurus were still smaller by a few tons. T. rex had laughably puny arms, but powerful haunches and a head like a battering ram full of pincers. Its skull alone was longer than your average human, and its mouth was filled with over 50 serrated teeth, as big as bananas but rock-hard. A T. rex eyeball would have been the same size as a grapefruit, and its ear hole the same size as a bottle cap.

What most people don’t know about T. rexes is that they had feathers—just a light layer of fluff akin to hair that helped retain body heat, attract mates, and intimidate rivals. T. rexes also had similar lung structure to birds. Like birds, the T. rex’s lungs were anchored to its backbone and it could take in oxygen on the inhale and the exhale. The T. rex needed all the help it could get: There’s no doubt that Jurassic Park’s chase scenes made for exciting cinema, but the T. rex wouldn’t have been able to sprint or turn quickly. It would have waited for the right moment to take a swift strike.   

The King was also a wanderer. Fossil records suggest that T. rexes originated in China, crossed the land bridge connecting Russia and Alaska, and meandered south through Canada into the middle of what today is called America. This was the ultimate invasive species. The T. rexes had no significant competition and readily displaced the diminutive apex predators that had ruled North America.

The King’s reign was short and sweet—starting about 68 million years ago and lasting about 2 million years. In the end, it took something extraterrestrial to dethrone the King.

What happened the day the dinosaurs died? Evidence points very strongly to a comet or asteroid crashing into today’s Yucatan Peninsula in Mexico. The asteroid was about 6 miles wide, roughly the same size as Mount Everest. It was moving at a velocity 100 times faster than a jet (almost 70,000 miles per hour), and it smashed into Earth with the equivalent power of a billion atom bombs. It crashed through the Earth’s crust and was buried 25 miles below the surface, well-ensconced in the mantle. To this day, there’s an enormous crater in Cancún, Mexico, half on land, half in the water, where the asteroid made landfall.

What would the moment of extinction have been like if you were there 66 million years ago? Let’s say you were a sentient, self-aware T.rex, living in the North American West, about 2,000 miles away from Cancún, Mexico, at that time. The asteroid has been visible to you weeks leading up to the moment of impact, a glowing, growing dot in the sky.

On the day of impact, the asteroid looms large and is bright enough to light up the sky to the south. At the moment of impact, you see a flash. It’s perfectly silent, but the sky immediately turns bright yellow. Then, there’s a second, more intense flash of light. The rays are bright enough to burn your retinas. A few seconds later there’s still no sound, but the ground beneath you begins to tremor slightly, then violently. A throbbing energy moves across the ground in wave-like undulations, sending rocks, trees, and even your 7-ton self hurtling through the air. At this point, most of the dinosaurs around you are dead—skulls cracked and spines split.

The bright yellow sky turns orange and then red. The red becomes more and more saturated and brighter. Then commences a shower of tiny, white-hot glass shards from the asteroid that burn and slash through dinosaurs. These shards give off their heat to the atmosphere as they break off from the asteroid and are launched into space, turning the planet into an oven. It’s hot enough for forests to spontaneously combust. The sky turns black from all the dust and smoke that’s been kicked up from the asteroid and the wildfires.

It’s only been 15 minutes since you first saw the light. The temperature is dropping again, it’s no longer raining glass, and the earthquakes have stopped. After two more halcyon hours, the winds pick up: tornados and hurricanes, followed by a boom that is so loud, it ruptures the ear drums of any animal that didn’t take shelter underground. It’s the sonic boom emanating out from the epicenter in Mexico, reaching the Northwestern United States well after the first frightening visuals. Near the surrounding coasts, tsunamis are growing to heights double that of the Empire State Building.

This gives us an idea of what it might have been like that day. It’s slightly dramatized, but not exaggerated. This scene is the most likely scenario, based on scientists’ best understanding of physics, astronomy, and meteorological principles. And this was thousands of miles away from the epicenter. Researchers suspect that everything within 600 miles of the point of impact was completely vaporized on impact. For a T.rex in Montana, the fallout (blinding flash of light, earthquakes, wildfires, hurricanes, tornados, earsplitting sonic booms, extreme heat and extreme cold) was all relatively minor.

This goes over most people’s heads (pun intended), but there are still plenty of dinosaurs around. Anytime you hear gulls screeching along the coast or a songbird chirping in the trees overhead, you are encountering surviving dinosaurs. Sure, they look completely different from the dinosaurs that populate popular imagination, but the link is there. In the same way that bats look nothing like cheetahs or elephants, but are still classified as mammals, birds belong to the dinosaur family even though they look dramatically different than Stegosauruses or Brontosauruses. They’re just a strange subset of dinosaurs that managed to develop wings, fly, and survive the apocalypse that took out just about everything else.

The connection between birds and dinosaurs is more robust than you might think. There’s fossil evidence that birds weren’t the only dinosaurs with feathers: As mentioned earlier, T. rex and others had feathers, too. Velociraptors would have been covered in feathers—rather than scaled from head to claw like we see in movies. The idea of feathered dinos has been floating around since Darwin’s day in the mid-1800s, but it’s only been the past several decades that have confirmed the link between birds and dinosaurs, with fossils showing wings and feathers of a bird, with the tail and razor-like teeth of a reptile.

The discovery that birds are dinosaurs could be the most important piece of the evolutionary puzzle that dinosaur hunters have made in the history of the field.

These insights are just an introduction. If you're ready to dive deeper, pick up a copy of The Rise and Fall of the Dinosaurs here. And since we get a commission on every sale, your purchase will help keep this newsletter free.