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 holes in front of us were fossilized tracks, huge ones. Dinosaur tracks, no doubt. As we looked closer, we could see that there were both handprints and footprints, and some of them had finger and toe marks. They had the telltale shape of tracks left by sauropods. We had found a 170-million-year-old dinosaur dance floor, records left by colossal sauropods that were about fifty feet long and weighed as much as three elephants.

they considered the sauropod bones to belong to the one type of thing they knew could get so huge: whales. It was a few decades before that mistake was corrected. Amazingly, later discoveries would show that many sauropods got even bigger than most whales. They were the largest animals that ever walked the land, and they push the limit for what evolution can achieve.

how did sauropods become so large? It’s one of the great puzzles of paleontology.

Barosaurus.

Brontosaurus at the American Museum of Natural History in New York, with a human skeleton for scale.

The primitive proto-sauropods like Plateosaurus began to experiment with relatively large sizes in the Triassic, as some of them got up to about two or three tons in weight. That’s roughly equivalent to a giraffe or two. But after Pangea started to split, the volcanoes erupted, and the Triassic turned into the Jurassic, the true sauropods got much larger. The ones that left tracks in the Scottish lagoon weighed about ten to twenty tons, and later in the Jurassic, famous beasties like Brontosaurus and Brachiosaurus expanded to more than thirty tons. But that was nothing compared to some supersize Cretaceous species like Dreadnoughtus, Patagotitan, Argentinosaurus—members of an aptly named subgroup called the titanosaurs—which weighed in excess of fifty tons, more than a Boeing 737.

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. So they needed a way to gather and digest such vast quantities of grub. Secondly, they need to grow fast. Growing bit by bit, year by year is all well and good, but if it takes you over a century to get big, that’s many opportunities for a predator to eat you, or a tree to fall on you during a storm, or a disease to take you out long before you grow into your full-size adult body. Third, they must be able to breathe very efficiently, so they can take in enough oxygen to power all of the metabolic reactions in their immense bodies. Fourth, they need to be constructed in a way that their skeleton is strong and sturdy, but also not so bulky that it can’t move. Finally, they need to shed excess body heat, because in hot weather it is very easy for a big creature to overheat and die.

Studies of bone growth indicate that most sauropods matured from guinea-pig-size hatchlings to airplane-size adults in only about thirty or forty years,

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.

We know a lot about the dinosaurs of the Late Jurassic. That’s because there are abundant fossils from this time, in many parts of the world. It’s just one of those quirks of geology: some time periods are better represented in the fossil record than others. It’s usually because more rocks were being formed during that time, or rocks of that age have better survived the rigors of erosion, flooding, volcanic eruptions, and all of the other forces that conspire to make fossils difficult to find.

When it comes to the Late Jurassic, we enjoy two lucky breaks. First, there were hugely diverse communities of dinosaurs living alongside rivers, lakes, and seas all around the world—the perfect places to bury fossils in sediments that later turned to rock. Second, these rocks are today exposed in places convenient for paleontologists—in sparsely populated and dry regions of the United States, China, Portugal, and Tanzania, where annoyances like buildings, highways, forests, lakes, rivers, and oceans don’t cover up the fossil booty.

University of Chicago’s Paul Sereno,

like any academic paleontologist, Paul also had to spend time in the classroom. Each year he taught a popular undergraduate class called Dinosaur Science, which combined theory with practice.

the so-called Bone Wars led to the discovery of some of the most celebrated dinosaurs, the ones that roll off the tongue of every schoolchild: Allosaurus, Apatosaurus, Brontosaurus, Ceratosaurus, Diplodocus, Stegosaurus, just to name a few.

Barnum Brown, a New York paleontologist passing through town. We’ll meet Brown again in the next chapter, because much earlier in his career he discovered Tyrannosaurus rex.

Brown liked what he saw and stayed the week. What he found was promising enough to convince Sinclair Oil to fund a full-scale expedition in the summer of 1934, to dig up what is now called the Howe Quarry. It turned out to be one of the most fantastic dinosaur excavations of all time.

The diggers found an entire ecosystem preserved in stone: there were giant long-necked plant-eaters like Diplodocus and Barosaurus, entangled with sharp-toothed Allosauruses and smaller herbivores that walked on two legs, called Camptosaurus. Something horrible had happened here some 155 million years ago. Judging from the contorted angles of their skeletons, the deaths of these animals were neither quick nor painless. Some of the sauropods were found upright, their heavy legs standing tall like columns, stuck in the ancient mud. It seems that these dinosaurs survived a flood, but then were mired in the muck when they tried to run away after the waters receded.

fossil collector from Switzerland named Kirby Siber rolled into Wyoming in the late 1980s.

there is a whole spectrum of commercial paleontologists, ranging from gun-toting criminals who illegally export fossils to diligent, conscientious, well-trained collectors whose knowledge and experience rival that of academics. Siber is in this latter category. In fact, he’s the archetype of this kind of collector. He is well respected by researchers and even founded his own dinosaur museum east of Zurich, called the Saurier Museum, which has some of the most remarkable dinosaur exhibits in Europe.

Siber followed the spool-shaped bones, one by one, and before long it was clear that he had something special: the nearly complete skeleton of an Allosaurus, the top predator of the Morrison Formation ecosystem. It looked to be the single best fossil of this well-known dinosaur that had ever been found, more than 120 years after Marsh first named it during the heat of the Bone Wars.

Computer models find that the thin teeth of Allosaurus couldn’t bite very strongly on their own, but the skull could withstand massive amounts of impact force. We also know that Allosaurus could open its jaws obscenely wide, so we think a hungry Allosaurus would attack with mouth agape and slash down at its prey, slicing through the skin and muscle with its thin but sharp teeth, which were lined up along its jaws like the blades of scissors. Many a Stegosaurus and Brontosaurus probably breathed its last this way. If for some reason the blood-lusting Allosaurus couldn’t quite knock off its victim using only its jaws of death, it could always finish the job with a couple of swipes of its clawed, three-fingered arms, which were longer and more versatile than the stubby little forelimbs of T. rex.

A gorgeous dinosaur skeleton was sitting in the ground, and the people who had found it and begun to excavate it couldn’t finish the job. So the agency assembled a crack team led by legendary paleontologist Jack Horner’s crew at Montana’s Museum of the Rockies (Horner is best known for two things: discovering the first dinosaur nesting sites in the 1970s and being the science advisor for the Jurassic Park films).

The Late Jurassic, then, was a time of global uniformity. The same suite of dinosaurs ruled every corner of the globe. Majestic sauropods divided food among them, reaching a peak of diversity unmatched by any other large plant-eaters in Earth history. Smaller plant-chewers prospered in their shadows, and a motley crew of meat-eaters took advantage of all of that herbivore flesh. Some, like Allosaurus and Torvosaurus, were the first truly giant theropods. Others, like Ornitholestes, were the founding members of that dynasty that would eventually produce Velociraptor and birds. The planet was sweltering and the dinosaurs were able to move around wherever they wanted. This was the real Jurassic Park.

145 MILLION YEARS ago, the Jurassic Period transitioned into the final stage of dinosaur evolution, the Cretaceous Period. Sometimes the switch between geological periods happens with a flourish, as when the megavolcanoes closed out the Triassic. Other times, it’s barely noticeable, and more a matter of scientific bookkeeping, a way for geologists to break up long stretches of time without any major changes or catastrophes. The changeover between the Jurassic and Cretaceous is that type of boundary.

By about 125 million years ago, some 20 million years after the Jurassic ended, a new Cretaceous world had emerged, ruled by a very different suite of dinosaurs. The most obvious change had to do with the most prominent dinosaurs—the gargantuan sauropods. Once so diverse in the Late Jurassic Morrison ecosystems, the long-necks suffered a crash in the Early Cretaceous. Almost all of the familiar species like Brontosaurus, Diplodocus, and Brachiosaurus went extinct, while a new subgroup called the titanosaurs began to proliferate, eventually evolving into supergiants like the middle Cretaceous 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. But despite the outlandish sizes of the new Cretaceous species, never again would sauropods be as dominant as they were in the Late Jurassic; never again would they boast such a variety of necks and skulls and teeth that allowed them to exploit so many ecological niches.

My family tree of carcharodontosaurs helped me unravel their evolution. First, it clarified where these colossal carnivores came from and how they rose to glory. They got their start in the Late Jurassic and are very close relatives of that most terrifying predator of the Jurassic, the Butcher itself, Allosaurus. In effect, they evolved from a legion of hypercarnivores that was already incumbent in the apex predator niche, and then they escalated things further by becoming larger, stronger, and fiercer when their ancestors went extinct at the end of the Jurassic, 145 million years ago, during that long night of environmental and climate change. Did they drive these other allosaurs to extinction or take advantage when they succumbed for other reasons? We don’t yet know the answer. In either event, the carcharodontosaurs found a way to usurp the place of their forebears and, as the Cretaceous dawned, the kingdom was now theirs. For the next 50 million years or so, deep into the middle Cretaceous, the carcharodontosaurs ruled the world.

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

as ferocious as these carcharodontosaurs were, they wouldn’t stay on top forever. Living alongside them, in their shadows, was another breed of carnivore. Smaller, faster, brainier. Their name, the tyrannosaurs. They would soon make their move and begin a new dinosaur empire.

T. rex itself has been in the limelight for over a century, since it was first discovered in the early 1900s. It’s the king of dinosaurs, a forty-foot-long, seven-ton behemoth on a first-name basis with almost everyone on the planet. Later during the twentieth century, scientists discovered a few close relatives of T. rex that were also impressively large and realized that these big predators formed their own branch of dinosaur genealogy, a group that we called the tyrannosaurs (or Tyrannosauroidea in formal scientific parlance). However, paleontologists struggled to understand when these fantastic dinosaurs originated, what they evolved from, and how they were able to grow so large and reach the top of the food chain. These questions have remained unanswered until now.

Over the last fifteen years, researchers have recovered nearly twenty new tyrannosaur species at locations the world over. The dusty southern Chinese construction site that yielded Qianzhousaurus is one of the least unusual places where a new tyrannosaur has been found. Other new species have been pried from the sea-battered cliffs of southern England, the frigid snowfields of the Arctic Circle, and the sandy expanses of the Gobi Desert. These finds have allowed my colleagues and me to build a family tree of tyrannosaurs in order to study their evolution. The results are surprising.

Brown will always be remembered as the man who discovered Tyrannosaurus rex, but this was just the start of his career. He developed such an eye for fossils that he steadily progressed from a fossil-collecting grunt worker to the curator of vertebrate paleontology at the American Museum, the scientist in charge of the world’s finest dinosaur collection. Today, if you visit its spectacular dinosaur halls, many of the fossils you’ll see were collected by Brown and his teams. No wonder that Lowell Dingus, one of my former colleagues in New York who wrote a biography of Brown, refers to him as “the best dinosaur collector who ever lived.” This sentiment is shared by many of my fellow paleontologists.

Barnum Brown, who worked for Osburn.

our new understanding of tyrannosaur evolution stems from a wealth of new fossils. Many of these have come from unexpected locales, perhaps none more so than what is currently recognized as the very oldest tyrannosaur, a modest little critter called Kileskus that was discovered in 2010 in Siberia. When you think of dinosaurs, Siberia is probably not a place that comes to mind, but their fossils are now being found throughout the world, even the far northern reaches of Russia, where paleontologists need to cope with harsh winters and humid, mosquito-infested summers.

To me, though, Kileskus is one of the most interesting discoveries of the last decade, because it is clear proof that tyrannosaurs had gotten an early evolutionary start. Kileskus was found in rocks formed during the middle part of the Jurassic Period, about 170 million years ago, more than 100 million years before T. rex and its colossal cousins were at the top of their game in North America and Asia.

Sinotyrannus lived about 60 million years before T. rex, a time when every other tyrannosaur we knew of could fit in the back of a pickup truck. Could this one find really rewrite tyrannosaur history? I had the sinking feeling that this fossil would remain a problem for a long time. This happens all too often in the field of dinosaur research: a single fossil emerges that hints at a major evolutionary story—the oldest member of a major group, or the first fossil to exhibit a really important behavior or feature of the skeleton—but it’s too broken or incomplete or poorly dated to be certain. Then another fossil is never found and it’s just left hanging, a cold case waiting to be solved.

There was something else peculiar about Yutyrannus.

These are feathers. Not the quill-pen feathers that make up the wings of today’s birds but simpler ones that look more like strands of hair. These were the ancestral structures that bird feathers evolved from, and it is now known that many (and perhaps all) dinosaurs had them. Yutyrannus and Dilong establish beyond a doubt that tyrannosaurs were among these feathered dinosaurs. Unlike birds, tyrannosaurs certainly were not flying. Instead, they probably used their feathers for display or to keep warm. And because both a large tyrannosaur like Yutyrannus and a small tyrannosaur like Dilong have feathers, this implies that the common ancestor of all tyrannosaurs had feathers, and therefore that the great T. rex itself was most likely feathered, too.

During the final 20 million years of the Cretaceous, tyrannosaurs flourished, ruling the river valleys, lakeshores, floodplains, forests, and deserts of North America and Asia. There is no mistaking their signature look: huge head, athletic body, sad arms, muscular legs, long tail. They bit so hard that they crunched through the bones of their prey; they grew so fast that they put on about five pounds every day during their teenage years; and they lived so hard that we have yet to find an individual that was more than thirty years old when it died. And they were impressively diverse: we have found nearly twenty species of these big-boned tyrannosaurs from the latest Cretaceous, and there are surely many more out there waiting to be discovered. The Pinocchio-nosed Qianzhousaurus, so fortuitously discovered by that still-anonymous backhoe operator at the Chinese construction site, is one of the latest examples.

A map from this time would have looked quite a bit like today’s globe. There were, however, some major differences. Due to sea-level rise in the Late Cretaceous, North America was bisected by a seaway stretching from the Arctic to the Gulf of Mexico, and a flooded Europe was reduced to a smattering of small islands. T. rex’s Earth was a fragmented planet, with different groups of dinosaurs living in separate areas. As a result, champions in one region might not be able to conquer another for one simple reason: they couldn’t get there. Colossal tyrannosaurs never seemed to gain a foothold in Europe or the southern continents, where other groups of large predators prospered, but in North America and Asia, tyrannosaurs were unrivaled.

its mouth, there were about fifty pointy teeth inside, each the size of a railroad spike.

T. Rex. Tyrannosaurus Rex.

Tyrannosaurus rex—the King of the Dinosaurs, the largest predator that has ever lived on land in the 4.5-billion-year history of Earth.

T. REX IS a celebrity character—the nightmare haunter—but it was also a real animal. Paleontologists know quite a lot about it: what it looked like, how it moved and breathed and sensed its world, what it ate, how it grew, and why it was able to get so big. In part, that’s because we have a lot of fossils: over fifty skeletons, some nearly complete, more than for almost any other dinosaur.

T. rex was huge: adults were about forty-two feet (thirteen meters) long and weighed in the ballpark of seven or eight tons, based on those equations from a few chapters ago, which calculate body weight from the thickness of the thighbone.

Giganotosaurus, for example, was about as long as T. rex and may have reached about six tons. But that’s still a good ton or two lighter than Rex, so the King stands alone as the biggest purely meat-eating animal that lived on land during the time of dinosaurs, or indeed at any time in the history of our planet.

T. rex lived from about 68 to 66 million years ago, and its dominion was the forest-covered coastal plains and river valleys of western North America.

Then one day it all ended. T. rex was there when the asteroid fell down from the sky 66 million years ago, putting a violent end to the Cretaceous, exterminating all of the nonflying dinosaurs.

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. It defies common sense that an agile and energetic animal with a knife-toothed head nearly the size of a Smart car wouldn’t use its well-endowed anatomy to take down prey but would just walk around picking up leftovers. It also runs against what we know about modern carnivores: very few meat-eaters are pure scavengers, and the outliers that do it well—vultures, for instance—are fliers that can survey wide areas from above and swoop down whenever they see (or smell) a decaying body. Most carnivores, on the other hand, actively hunt but also scavenge whenever they have the chance.

T. rex was probably both a hunter and an opportunistic scavenger.

There’s fossil evidence that proves T. rex hunted, at least part of the time. Many of those Triceratops and Edmontosaurus bones pockmarked with T. rex tooth impressions show signs of healing and regrowth, so they must have been attacked while alive but survived.

dinosaurs could replace their teeth throughout life (unlike us), no predator would want to break its chompers every time it ate. T. rex was different, though. Its bite marks are more complex: they start with a deep circular puncture, like a bullet hole, which grades into an elongate furrow. This is a sign that Rex bit deeply into its victim, often right through the bones, and then ripped back. Paleontologists have come up with a special term for this style of eating: puncture-pull feeding.

Thick peg-like teeth, huge jaw muscles, and a rigidly constructed skull: that was the winning combination. Without any of these things, T. rex would have been a normal theropod, slicing and dicing its prey with care. That’s how the other big boys did it—Allosaurus, Torvosaurus, and the carcharodontosaurs—because they didn’t have the arsenal necessary for bone-crunching. Once again, the King stands alone.