One Dragons of the Prime " Brontosaurus " will always be special to me. For my younger self, especially, the shuffling, swamp-dwelling hulk was an icon of everything dinosaurs were supposed to be--big, scaly, and, most of all, so thoroughly bizarre that they could only have belonged to a primeval past. And, though dead for over 150 million years, " Brontosaurus " lived on in my imagination. From the time I was a toddler, I desperately wanted to meet the gigantic herbivore. In my preschool scribblings, I included a pet " Brontosaurus " in crayoned portraits of my family. I kept it reasonable. I knew we could never afford an eighty-foot dinosaur, so I went with a Bronto roughly the size of a Great Dane. She was big enough to let me ride on her back, but small enough that my parents wouldn't go poor providing appropriate forage for my friend. Resuscitating the dinosaur in Crayola colors barely even touched the depths of my dinomania. When my parents drove my siblings and me to Disney World for the first time, I so fiercely harried them about seeing the animatronic " Brontosaurus ," Stegosaurus , and kin at the Exxon-sponsored Universe of Energy attraction that Mom and Dad didn't even unpack the car before putting us on the right bus to see the dinosaurs. Forget Mickey and Minnie. The jerking, wailing robotic dinosaurs were at the top of my list. And while I would later curse being stuck in the mind-numbingly mundane confines of central New Jersey, my captivity in the suburban sprawl carried at least one advantage. There was scarcely a better place for a young dinosaur fan than the nearby American Museum of Natural History, just over the river in New York City. That's where I first met my favorite dinosaur. The museum no longer looks like it did when my parents guided my younger self up to the fourth-floor dinosaur halls in 1988. Today, the white walls, high ceilings, and ample illumination make the skeletons of Tyrannosaurus , Edmontosaurus , Triceratops , and other dinosaur celebrities stand out in sharp contrast from their surroundings. This open, airy vibe was created by a renovation project in the mid-1990s to adjust the prehistoric stars in accordance with new discoveries. Arranged in an evolutionary rank and file, the revised halls are a testament to how much dinosaurs have changed since nineteenth-century naturalists first recognized them. The AMNH dinosaurs stand alert, skeletal heads and tails at attention as if they're scanning a vanished landscape for food, friend, or foe. During my early twenties, when I had the freedom to visit whenever I pleased, I took any chance I could get to wander among these skeletons and imagine flesh on their bones. And, as I strolled through those halls, the floors scuffed by the feet of so many youngsters on their first trips into the presence of dinosaurs, what I missed most was the dim, dusty Jurassic Dinosaur Hall that I encountered so many years before. The old dinosaurs were horribly wrong when I viewed them back in the 1980s--awkward aberrations ultimately sent to the scientific trash heap--but that doesn't diminish my memory of seeing them for the first time. Way back then, in the forbidding gloom of the hall, my imagination gave the bones a thin cast of vitality. The skeletons felt less like perished monuments to paleontology and more like bony scaffolding waiting to be connected by sinew and wrapped in scaly hides. My young mind didn't see dead dinosaurs, but the osteological architecture of creatures that might walk again. * * * I was so consumed by the idea during my first trip to the AMNH that I can hardly remember my parents being there. Standing beneath the prehistoric skeletons, I was entranced. I couldn't take my eyes off the museum's " Brontosaurus ," with her neck stretched low, tipped with a moronic blunt skull full of spoon-shaped teeth. I was in the court of the queen of all sauropods--the long-necked, heavy-bodied dinosaurs that were the largest creatures ever to walk the Earth. After all, as my schoolbooks told me, " Brontosaurus " was so massive that her name meant "thunder lizard." When she walked, it must have sounded like a storm rolling across the Jurassic landscape. I imagined that sound as I admired her skeleton. She seemed poised to step off the platform, duck out the exit, and plod right down to the foliage along Central Park West. In the intense quiet of that moment, I could have sworn that I heard the ethereal remnant of the dinosaur's breathing. In a place with so many prehistoric bones, there had to be ghosts. Yes, the old mounts of Tyrannosaurus and other dinosaurs were impressive, too. But they didn't stick with me quite like the " Brontosaurus ." I couldn't help but wonder what it would have been like to catch a glimpse of the dinosaur trundling down my street, picking succulent leaves from the oaks of my neighbors' lawns. I drew sluggish brontosaurs in my school art portfolios, made my plastic sauropod models bask in an improvised mud puddle I created in the driveway's storm drain, and dreamed of some far-off swamp where the dinosaur might still sun itself, enjoying a reprieve from extinction. And then I heard the bad news. * * * " Brontosaurus " was dead to begin with. My favorite dinosaur wasn't real, but only a misconstrued amalgamation that had been borne and slaughtered by science. The dinosaur's true name was Apatosaurus --a creature that paleontologists envisioned as vastly different from my brontosaur. Apatosaurus was not a waterlogged grubber of algae and water lilies, but in fact was a taut, active animal that trod Jurassic floodplains with its neck and extended whiplash tail held high off the ground. " Brontosaurus " as I knew the beast--a hulking pile of flesh and bone that bathed in Jurassic swamps--never actually existed. Almost everything about the monstrous creature--its lifestyle, its skull, and, most regrettably, its name--were human inventions drawn from prehistoric skeletons that actually supported a different form. I had been fooled! The dinosaur I met was a petrified museum zombie, shuffling on even though scientists had shot it down decades before. You see, the dinosaur's major makeover wasn't easy, and it wasn't fast. I had encountered the brontosaur only as it was slowly fading from books and museum halls. A few years before I made my first museum visit, a groundswell of scientific interest in sauropods, stegosaurs, tyrannosaurs, and their varied kin--given the dramatic title "The Dinosaur Renaissance"--had crushed the image of dinosaurs as stupid, abominable reptiles and recast them as animals that had more in common with birds than with any lizard or crocodylian (a term for the group encompassing alligators, crocodiles, and gharials). The fossil bones were the same as they ever were, but paleontologists saw the petrified remnants in a new light. And in the special case of " Brontosaurus ," the dinosaur's name, skull shape, and cultural identity are all bound together in a complicated knot where science and imagination meet. The story started over a century ago during one of the most fruitful times in the history of paleontological discovery. In 1877, the Yale paleontologist Othniel Charles Marsh applied the name Apatosaurus ajax to the partial skeleton of a juvenile sauropod that Arthur Lakes, later one of Marsh's field assistants, had discovered in Colorado. Two years later, Marsh coined Brontosaurus excelsus on the basis of a more complete skeleton his men had found, this time at Como Bluff, Wyoming. The dinosaurs were only subtly different, but in Marsh's day, paleontologists interpreted even the slightest of skeletal differences as indicators of previously unknown genera and species. After all, Marsh and his contemporaries were among the first to scientifically catalog a prehistoric lost world full of creatures no one had ever seen before. Who could say how many different forms there were? In 1896, the paleontologist O. C. Marsh published this reconstruction of " Brontosaurus " excelsus in his major monograph The Dinosaurs of North America . (Image from Wikimedia Commons: en.wikipedia.org/wiki/File:Brontosaurus_skeleton_1880s.jpg) In this case, though, what Marsh thought were two different dinosaur genera were merged into one. In 1903, the paleontologist Elmer Riggs argued that Marsh's " Brontosaurus " wasn't distinct enough from Apatosaurus to justify a new genus name. The " Brontosaurus ," Riggs reasoned, was only a new species of Apatosaurus , and since Apatosaurus was named first, it had priority of title. Thus " Brontosaurus " excelsus became Apatosaurus excelsus . The trouble was that the name change didn't filter from technical journals to pop culture (or, clearly, to museum displays). As institutions such as the AMNH erected Apatosaurus skeletons, they slapped the mounts with the old " Brontosaurus " label for reasons that have never been resolved. Maybe they thought the old name sounded better, or were unsure about rebranding one of the most famous dinosaurs in their halls. Whatever the reason, " Brontosaurus " was given a second life. For the moment, let's follow the lead of Riggs's stubborn contemporaries and call the animal " Brontosaurus. " In general form, the " Brontosaurus " skeletons museums so proudly displayed weren't very different from other huge sauropods, such as Diplodocus . These two dinosaurs--who lived alongside each other in western North America about 150 million years ago--shared the same body plan, with " Brontosaurus " being a bit bulkier than its more slender counterpart. What made " Brontosaurus " different, and seemed to characterize the dinosaur's personality, was its skull. When I met the skeletal " Brontosaurus " in 1988, the dinosaur's neck was capped with a skull that made it look about as dumb as early-twentieth-century scientists insisted the animal must have been. As the AMNH paleontologist William Diller Matthew wrote, "We can best regard the Brontosaurus as a great, slow-moving animal automaton, a vast storehouse of organized matter directed chiefly or solely by instinct, and to a very limited degree, if at all, by conscious intelligence." To my mind, this man, who oversaw the construction of the mount I was so fascinated by, viewed the dinosaur as a bad evolutionary joke, a heavyweight that was all brawn and no brain. Unbeknownst to me at the time of my first museum trip, this reptile's skull was a conglomeration of bone fragments and speculation. * * * When Marsh's field crew discovered the original " Brontosaurus " material at Como Bluff, they were frustrated that the specimen lacked a cranium. (Sauropods had a habit of losing their heads between their death and burial.) So, when it came time for Marsh to commission an illustration of what the animal's skeleton would have looked like, he drew on several skull bones found at another Como Bluff quarry. These pieces actually came from a different animal--a short-snouted, high-skulled sauropod called Camarasaurus that lived at the same time--but Marsh didn't know that. He assumed that the skull and skeleton belonged to the same animal, and so he used the fragments to re-create a " Brontosaurus " skull. Other museums followed suit. It was years before anyone found the dinosaur's true skull. * * * The beginning of the end for " Brontosaurus " goes back to Dinosaur National Monument, one of the richest boneyards ever found. You know you're getting close to the park when goofy, tourist-trap dinosaurs start appearing along Highway 40 in Vernal, Utah. You can't miss them. Some of them snarl, others pose outside hotels, and my favorite--a rendition of the town's long-necked mascot Dinah--wears a polka-dot bikini and stands above a sign that reads: "Let's swim!" Dinosaurs didn't have mammary glands, so I'm not sure what good a bikini top would do. Maybe that's just the Utah sense of modesty at work. Vernal's dinosaurs have a gleefully outdated feel. They're mostly holdouts from an earlier era, from a tourism boom after a glass-walled museum was erected over Dinosaur National Monument's quarry of bones in 1957. The protected excavation was the dream of Earl Douglass--the man who struck a rich vein of fossils among the area's rocky hills in 1909, and extensively quarried the site under the employ of Pittsburgh's Carnegie Museum of Natural History. Even though Douglass shipped tons of bones back east, he wanted the enormous bonebed to become a living museum where visitors could come and see paleontology in action. Some of his dreams--such as an airstrip on the site and fine dining for high-class clientele--didn't come to pass, but the heart of his vision was realized and continues to show visitors that prehistory can seem as alien as another world. Cruise past decaying rock shops, a few more cracked and faded dinosaurs, and emerald swaths of farmland that spring from the banks of the Green River, and you'll finally arrive at the park. A dopey Diplodocus grins sheepishly at visitors from a parking lot just outside the park limits. And if you know your geology, the winding drive to the recently renovated museum is a literal trip through time. Millions of years of deposition, uplift, and erosion cracked the depths of the earth into a series of sharp slices, each sliver older than the last. Remnants of ancient oceans transition into traces of fern-covered floodplains, divided from the vestiges of dune-filled deserts by the incursion of another vanished sea, and so on down through time. Even if you're not well versed in the paleontological particulars, you can follow the changes by color. Each formation is set off from the others by its own range of hues, from mint green to rust red. I could never dream of a more wondrous landscape. This is one of the most beautiful places on Earth. The road leading up to the quarry wall is a mixture of maroon slices interspersed through grayish-purple stacks. This is the classic color scheme of the Morrison Formation, the roughly 150-million-year-old deposits that herald the presence of dinosaur giants. This was the era of Stegosaurus , Allosaurus , Diplodocus , Brachiosaurus , Ceratosaurus , and many other favorites, including--of course--the dinosaur formerly known as " Brontosaurus ." Picking out each species on the sheltered quarry wall isn't easy for anyone who doesn't have an encyclopedic knowledge of dinosaur anatomy. The exposed rock face is a logjam of bones created by an unfortunate twist of Mesozoic fate. Dozens of dinosaurs died in a Jurassic drought, and when the rainy season finally broke the dry spell, the bodies of the poor dinosaurs were washed together into this one place. Disembodied limbs and segments of tail are interspersed with isolated skeletal elements in a slurry of tan-shaded bone. Bad luck for the dinosaurs, but a bonanza for Earl Douglass and other paleontologists that followed him. The quarry was bigger a century ago. The slanted bonebed extended another one hundred feet upward, and another hundred feet to either side. Those portions were uncovered, excavated, and shipped to museums long ago. And while most dinosaurs in the quarry wound up as isolated bones and body parts, Douglass also exhumed a few complete skeletons. In September of 1909, not long after he stumbled on the string of dinosaur vertebrae that first called his attention to this place, Douglass excitedly picked away at what appeared to be a complete " Brontosaurus " skeleton. "We evidently have the most complete of the huge Dinosaurs that ever was found, at least I haven't heard of any other so complete as this appears to be," Douglass wrote back to the Carnegie staff. There was even the possibility that the dinosaur's long-lost skull might be at the end of the neck. "I am not sure," Douglass confided, "but believe now that we will get the head." The arc of the dead dinosaur's body pointed the way for Douglass. After two more months of excavating the skeleton, he found that the dinosaur's neck was thrown backward over the rest of the spinal column--the classic dinosaur death pose. If the skull was there, surely it would have been at the end of the arched neck. Douglass and his crew carefully uncovered the remainder of the neck "with beating hearts," and as he recounted to his boss William Holland, "I could almost see the skull I was so sure of it for was there not a series of 8 cervicals undisturbed and in natural position." But the neck stopped at the third or fourth neck vertebra. There was nothing else. "How disappointing and sickening," Douglass sighed. Douglass pushed forward regardless, continuing his work through the coming seasons. He even set up a permanent residence among the colorful outcrops, toiling through the brutal summer heat and enduring the winter chills that annually closed his field operations. And while no skull was ever found attached to a " Brontosaurus " neck, Douglass turned up a few isolated skulls of the hefty, long-necked sauropod dinosaurs. Most of these resembled the profile of Diplodocus . Instead of having blunt heads with spoon-shaped teeth, like Camarasaurus , Diplodocus had elongated, shallow skulls tipped with a squared muzzle of pencil-shaped teeth. But Douglass wasn't entirely sure all the skulls really belonged to Diplodocus . Perhaps some of the craniums in his collection truly belonged to " Brontosaurus "--still a headless dinosaur at the time. "Can we be positively certain that the supposed skull of Diplodocus is not that of Brontosaurus?" he wondered. Specifically, in 1910 Douglass discovered a puzzling skull very close to the neck of a second " Brontosaurus " specimen simply titled No. 40. Douglass believed that the fossilized cranium was a Diplodocus head that had rolled away from its owner after death, "though I would be glad to give a fellow [a] crown of glory if he'd convince me otherwise." He wasn't quite ready to go out on a limb and say that he had found--at long last!--the head of " Brontosaurus ." William Holland didn't think Douglass had found another Diplodocus noggin. He believed that his man in the Jurassic had indeed found the long-lost " Brontosaurus " head. The skull was similar to that of Diplodocus , so it was no surprise that Douglass's doubts threw him off the trail, but the " Brontosaurus " cranium looked a little wider and bulkier, befitting the heavier stature of the dinosaur. Holland argued that the established " Brontosaurus " skull form--assembled by Marsh from only a few fossil scraps--was totally wrong. The stout skull Douglass had found near dinosaur No. 40, Holland thought, truly did belong to the "deceptive lizard," properly called Apatosaurus . Scientific uncertainties and paleontological politics continued to complicate the legacy of Apatosaurus . Despite arguing that Douglass had finally found the dinosaur's skull, Holland decided to leave his museum's mount of the dinosaur headless, and the reconstruction stood that way for twenty years. Only in 1934, two years after Holland passed away, did the Carnegie Apatosaurus get a head, and it was a blunt Camarasaurus -like stand-in. No one seems to know who made the decision, but the choice reflected the consensus of the time--similar to Marsh's view--that Apatosaurus was a close relative of Camarasaurus . Due to their presumed affinity, the two dinosaurs would be expected to have similar skulls. The Carnegie dinosaur, along with its counterparts at Yale and the AMNH, smiled at visiting masses with a substitute head for years. And that peculiar skull Douglass had found next to skeleton No. 40 was placed in the collections of the Carnegie with Diplodocus on its label. Eventually, Douglass's tentative hunch and Holland's assertions were proven correct. In 1975, a physicist turned self-trained sauropod expert by the name of John McIntosh reviewed the various letters, notes, and quarry maps Douglass had composed and confirmed that Douglass's strange " Diplodocus " head was found right up against an Apatosaurus skeleton. McIntosh described the skull in a paper outlining the fossil's distinct anatomy, and finally put the last, essential piece of Apatosaurus in place. On October 20, 1979, the Carnegie officially replaced the incorrect skull with a cast of the rediscovered Apatosaurus fossil. Other museums took a little bit longer to fix their mounts. Yale's Peabody Museum exchanged skulls in 1981 ("This is the first head transplant that I've ever performed," the paleontologist John Ostrom quipped as he put the new skull on the skeleton), and the AMNH fixed theirs much later on, during the mid-nineties revamp. Sure, paleontologists already knew that Apatosaurus was the proper name for the dinosaur when the skull switches happened. Riggs had settled that issue in 1903, and various papers cemented the technicality, but even though Riggs made it crystal clear, " Brontosaurus " lived on. Tyrannosaurus rex might be the undisputed favorite now, but " Brontosaurus " ruled the early days of cinema and has left a sizable imprint on the cultural landscape. Gertie the Dinosaur , one of the first animated features, starred a frisky dinosaur based on the American Museum of Natural History's " Brontosaurus ." More monstrous brontosaurs would later threaten humans in 1925's The Lost World and the 1933 classic King Kong . (Not to mention Cary Grant's frustrated search for the dinosaur's "intercostal clavicle"--a bone that doesn't actually exist--in 1938's Bringing Up Baby .) And that galumphing, sometimes aggressive personality was encapsulated by that fabricated skull. When the proper skull was placed on the dinosaur's body--just as paleontologists were revising the essence of what dinosaurs were--the animal's entire demeanor changed. Apatosaurus excelsus as we know the dinosaur today. (Illustration by Scott Hartman) By now, we know that Apatosaurus is the dinosaur's proper name. If you note the wrong term in front of a young fossil fan, you'll get a swift correction. But you can't keep a brontosaur down. Everyone knows the dinosaur's name and we want " Brontosaurus " to exist. Even though some of my paleontologist friends have tried to match the name's popularity by spreading the name of a previously unknown sauropod, Brontomerus --or "thunder thighs"--there isn't going to be another dinosaur that can fill the cultural gap " Brontosaurus " left behind, which is funny, since it's not like there's some " Brontosaurus "-shaped hole in prehistory. Just look at Google's Ngram Viewer--a service that tracks word use in books through time. We started using " Apatosaurus " and " Brontosaurus " at about the same time, but the Ngram reveals that " Brontosaurus " has always been the victor. Even from the 1970s on, when we knew that the dinosaur wasn't real, the name still beats Apatosaurus in frequency. Whenever we mention Apatosaurus , we feel compelled to remind everyone that the dinosaur used to be called " Brontosaurus ," and so the discarded name persists. (I'm certainly compounding the problem here.) We can't conjure Apatosaurus without the memory of " Brontosaurus " trailing close behind. The torturous episode reminds me of when Pluto was demoted from planet status to the dwarf planet level. The cosmic body is still out there--scientists didn't destroy it with a Death Star or other interplanetary weapon--but the outcry over the change was intense. Even many die-hard science fans loathed the technical decision. Why should a mundane label change matter so much? As the astronomer Mike Brown, whose work contributed to Pluto's fall from interstellar grace, put it: In the days that followed [Pluto's demotion], I would hear from many people who were sad about Pluto. And I understood. Pluto was part of their mental landscape, the one they had constructed to organize their thinking about the solar system and their own place within it. Pluto seemed like the edge of existence. Ripping Pluto out of that landscape caused what felt like an inconceivably empty hole. The Jurassic herbivore was a touchstone that put the rest of the archosaurian horde in context and helped us revive lost worlds in our imaginations. And the sauropod's apparition remains a cultural baseline against the ever-shifting image of what dinosaurs are. To my mind, we didn't lose a dinosaur so much as gain a much clearer view of a real Jurassic giant. The contrast between old " Brontosaurus " and dinosaurs as we know them now shows us just how much we have learned about dinosaur biology. * * * In order to appreciate how our understanding of dinosaurs has changed, though, we need to know what dinosaurs really are . That's not as simple as it sounds. Here's what dinosaurs are not: they are not just anything big, toothy, and prehistoric. A woolly mammoth wasn't a dinosaur, the leathery-winged flying reptiles called pterosaurs weren't dinosaurs, and fish-chasing aquatic reptiles such as the plesiosaurs and ichthyosaurs weren't dinosaurs. Just because an animal's name ends in "saur" doesn't necessarily mean it's a dinosaur. "Dinosaur" is a scientific term, not a colloquial one, and applies only to a restricted group of animals. The simplest way to visualize this is by picking two of the last members of each branch of the dinosaur family tree and tying them back to their last common ancestor. So if you were to take Triceratops and a pigeon (birds are dinosaurs, too) and go back to their last common ancestor, everything that rests within the resulting evolutionary tree would count as a dinosaur, all of them bound together by a mosaic of shared anatomical features. If an animal doesn't fall within those brackets, it's not a dinosaur. That's a strange way to think of delimiting dinosaurian identity, but the proof is in their evolutionary relationships. Let's dig a little deeper. The reason we pick Triceratops and a pigeon to outline the dinosaur family tree is because these animals represent the ultimate members of the two major dinosaur subgroups. The dyspeptic Victorian anatomist Harry Govier Seeley delineated these varieties in 1887 on the basis of dinosaur hips, of all things. While some dinosaurs (such as Allosaurus and Apatosaurus ) had roughly lizard-shaped hips, others (such as Stegosaurus ) had what Seeley thought were bird-like hips. He named the two varieties the Saurischia and Ornithischia, respectively (even though the latter name turned out to be ironic--although birds are dinosaurs, so-called bird-hipped ornithischian dinosaurs weren't anywhere close to avian ancestry). While the names don't exactly roll off the tongue, Ornithischia and Saurischia are essential labels for understanding who's who among the dinosaurs. All the dinosaurs we know of fall into one group or the other. The myriad of bizarre dinosaur forms is staggering. Among the Ornithischians were dome-heads like Pachycephalosaurus ; shovel-beaked hadrosaurs such as the crested form Parasaurolophus ; armored dinosaurs such as Ankylosaurus ; and Pentaceratops --a massive quadruped with curved brow horns and a flashy, elongated frill. As far as we know, all of these dinosaurs were principally herbivorous. The Saurischia, on the other hand, includes some of the largest, fiercest, and most charismatic dinosaurs of all. The two principal saurischian subgroups were the sauropodomorphs--long-necked herbivores that included Apatosaurus and its close kin--and the theropods. For a long time, "theropod" was synonymous with "carnivorous dinosaur," but that isn't true anymore. Tyrannosaurus , Allosaurus , and Giganotosaurus were all flesh-rending theropods, as were Velociraptor and its kin, but many theropod lineages became either omnivores or herbivores, and those include birds. While the carnivores have traditionally stolen the show, the weirdest theropods belong to recently discovered groups such as the alvarezsaurs--turkey-size dinosaurs thought to be the Mesozoic equivalent of anteaters--and potbellied feathery herbivorous dinosaurs with insanely long hand claws, called therizinosaurs. Our understanding of just how wildly divergent dinosaur body plans were is constantly changing. The word "dinosaur" technically includes everything from an Emperor penguin to one-hundred-foot behemoths such as Supersaurus, heavy-skulled bonecrushers like Tyrannosaurus , and spiky, armor-plated enigmas such as Stegosaurus . We probably don't even know the full span of dinosaur body types. Within the past three decades alone, paleontologists have identified several kinds of dinosaurs that we had no conception of before. The ant-eating alavarezsaurs and totally weird therizinosaurs are two such groups, but there are also the abelisaurids--theropods with short, deep skulls and wimpy arms that even a tyrannosaur would laugh at--and croc-snouted, sail-backed carnivores called spinosaurs. And that's to say nothing of the dinosaurs that lived after the mass extinction that closed off the Cretaceous, about 66 million years ago. Dinosaurs were not exclusively prehistoric animals--we now know that birds are the sole surviving dinosaur lineage. Indeed, birds are dinosaurs, but the majority of forms--the types that most immediately spring to mind when you think of the word "dinosaur"--are called non-avian dinosaurs. Many writers and paleontologists prefer to consider "non-avian dinosaur" and plain old "dinosaur" as synonyms because of the cumbersome jargon, but I think it's about time we came to terms with the technical language. Yes, it can be a little unwieldy, but we insult dinosaurs if we ignore the fact that they are still with us. To most people, "dinosaur" is something extinct. And recent discoveries--such as the spinosaurs and alvarezsaurs--are showing us how much there is left to be uncovered. Many of these discoveries have come from sites in South America, Africa, and Asia that were beyond the reach of early fossil hunters, but even North America and Europe--the continents that have been systematically sampled for the longest time--have yielded strange dinosaurs unlike anything anyone has seen before. All these fossil finds come from a distinct swath of prehistoric time. The Mesozoic span of the dinosaurs ran for more than 160 million years the world over. The dinosaurian heyday fell across three different geological periods--the Triassic (250 to 200 million years ago), the Jurassic (199 to 145 million years ago), and the Cretaceous (144 to 66 million years ago). That is a lot of time for evolution to usher new forms into existence. Even though we may never find all the dinosaur species, as some probably lived in habitats where there wasn't the right combination of factors for fossilization, there are certainly thousands of as-yet-unknown dinosaurs waiting to be found. Dinosaurs aren't only prehistoric animals, real monsters, or even objects of scientific scrutiny. They're icons and cultural celebrities. As the journalist John Noble Wilford wrote in The Riddle of the Dinosaur , "Dinosaurs, more than other fossils, are public property, creatures as much of the public imagination as of scientific resurrection." Dinosaurs invade our music, our movies, our advertising, and our idioms (although "going the way of the dinosaur" should really mean becoming undeniably awesome, rather than sinking into inevitable extinction). NASA even shot dinosaurs into space twice. Don't ask me what for, but they transported dinosaur fossils into space all the same--maybe because the creatures have so utterly entranced us and there's hardly a higher honor for our favorite monsters than for their bones to be granted a cherished place on a trip outside our atmosphere. With dinosaurs everywhere, it's no surprise that going through a "dinosaur phase" is a common and almost expected part of American culture. There's something about these creatures that has an immediate and inextricable appeal to children, and more than a few young dinosaur fans hold on to that passion to become paleontologists. I've never heard a good explanation for why this is. I don't buy the pop-psychology logic that dinosaurs are so celebrated because they are animals that are big and fierce, but safe because they're extinct. The appeal of dinosaurs doesn't just lie in our ability to conjure them up and banish them at will. There's something else at work, embedded in our curiosity about where we fit in the history of the world. Indeed, dinosaurs fueled rampant speculation about history and our place in it even before they had a name. From the Greeks to Native Americans, ancient cultures and aboriginal people concocted legends of hoary terrors and powerful heroes to explain the unusual animal bones they found crumbling out of the earth's crust, and the first English naturalists to describe dinosaurs saw them as fearsome, sharp-toothed reptiles of untold destructive power. Their remains were so strange and frightening that we instantly recognized they were primordial beasts that vanished long ago. More than anything else, the attractive essence of the dinosaurs lies in their bizarre and terrifying nature. We can't help wonder about creatures that, from the very start, we've envisioned as Tennyson's "Dragons of the prime, / That tare each other in their slime." Those images of dinosaurs easily become entrenched in our minds, even as science continues to revise what we thought we knew about them. * * * Our understanding starts with finding the dinosaurs themselves. We can't begin to reconstruct the identity of dinosaurs, and the details of their lives, without first collecting their bones. I thought about this undeniable fact, and the romance of fossil discovery, in 2011 as I stood on the balcony overlooking Douglass's old quarry, now cleaned and dusted to show off the mass graveyard in detailed relief. This is the heart of Dinosaur National Monument, and the crowded graveyard exemplifies the very beginning of our struggle to reconstruct dinosaur biology. The vista is the result of countless hours of work. For years, experts picked away at the rock face to expose the bones right in front of museum visitors. A view of life in Jurassic Utah, 150 million years ago. This was the habitat of Apatosaurus-- the bulky sauropod seen crossing the floodplain at center. (Art by Robert Walters and Tess Kissinger, courtesy of Dinosaur National Monument, Utah) Today, the work has stopped. Almost everything there is to find has been uncovered, and I'm a little disappointed that I can't watch the diligent fossil excavators go about their work (or even have a crack at carefully chipping out a few bones myself). Finding and digging dinosaurs is grueling, sweat-drenching work, punctuated by brief periods of excitement. When I'm in a quarry, in the lab, or in the field looking for dinosaurs in the rough, uncovering a fossil is an exhilarating experience--when my eyes settle on a freshly exposed bone or fragment, I can't help but wonder what sort of animal it belonged to and where it fit in the organism's skeleton. As George Gaylord Simpson, one of the greatest paleontologists of the twentieth century, once wrote: Fossil hunting is far the most fascinating of all sports. I speak for myself, although I do not see how any true sportsman could fail to agree with me if he had tried bone digging. It has some danger, enough to give it zest ... and the danger is wholly to the hunter. It has uncertainty and excitement and all the thrills of gambling with none of its vicious features. The hunter never knows what his bag may be, perhaps nothing, perhaps a creature never before seen by human eyes. Over the next hill may lie a great discovery!... The fossil hunter does not kill; he resurrects. And the result of his sport is to add to the sum of human pleasure and to the treasures of human knowledge. That same spirit is what led Earl Douglass to devote his life to uncovering his great Jurassic bonebed, and this romance fueled the institutional "My dinosaur is bigger than yours" contest that yielded splendid reconstructions of Apatosaurus --née " Brontosaurus "--in the exquisite museum halls of Pittsburgh, Chicago, and New York City. Those fantastic displays, like those all over the world, were petrified trophy rooms that showed off what toiling in the badlands might teach us about prehistory and our place in nature. The delicately mounted skeletons speak of a past so far beyond the reach of human memory that we can't even fully comprehend the depth of that time, and their stock-still skeletons place our own existence in context. (Consider this: Tyrannosaurus lived closer to us in time--66 million years ago--than it did to Apatosaurus , which lived 84 million years prior.) Indeed, although Douglass's dinosaurs gave his quarry its fame and eventual protection as a museum, the teeth and bones of tiny mammals are needles in this dinosaurian haystack. Our ancestors and cousins snuffled through the undergrowth and hid in the darkness of the Jurassic world, without so much as an inkling that the seemingly indomitable reign of the dinosaurs would someday end. * * * As fun as fieldwork can be, though, paleontology is far more than a trophy hunt. Finding a dinosaur is only the very start, and the little secret of fossil hunters is that if you pick the right geological setting, and can tell bone from rock, it's not all that hard to find dinosaurs. The exercise relies almost as much on luck as on science. And, after finding a few myself, I discovered that uncovering a dinosaur bone doesn't feel quite the way it's so often portrayed on television. In the endless stream of dinosaur documentaries I watched growing up, a paleontologist would often rhapsodize about being the first pair of eyes to see the freshly uncovered dinosaur bones in 66 million years or more. The scientists were apparently enthused just by the success of the hunt. But that's not what I thought about as I carefully scraped the sediment off a dinosaur femur in Ghost Ranch, New Mexico; when I plucked up a handful of dinosaur teeth in the ranchlands outside of Ekalaka, Montana; or even when I stared at Dinosaur National Monument's beautiful Jurassic cemetery. Dinosaur fossils are vestiges of ancient life. So many questions can be asked of even a single bone: how the dinosaur moved, what colors adorned its skin (or feathers), what the creature ate, how it died, and where it fit in the wider panorama of life on Earth, just to start. That's the passion of paleontology. Dinosaurs are old, yes, but they are also mind-bogglingly strange. The persistent questions about how such creatures could have evolved and thrived for so long are what drive me, and many other dinosaur fans, to keep digging into their history. And this is not just a dry academic exercise. This is personal. If I can uncover the secrets of their evolutionary success, maybe I can start to comprehend my endless fascination with them. * * * I had so many questions as a child that I was told we'd never answer. Slowly, and amazingly, we're starting to envision dinosaurs as they truly were. Paleontologists are painting a more intimate portrait of dinosaurs than has ever been composed before. The days of headhunting for prize skeletons and then leaving those bones to collect dust on museum shelves are over. The bones now form the basis of intense research programs that probe, scan, and dissect the fossil remains for whatever clues we can find about the lifestyles of the fierce and extinct. The Dinosaur Renaissance drastically changed dinosaur imagery, but, as the University of Maryland paleontologist Thomas Holtz once told me, it's the new Dinosaur Enlightenment that is outlining the details of how the animals lived. * * * Science is not just the stepwise accrual of facts that are written down and then forgotten. Fact and theory are intertwined, fostering our ever-changing perception of nature. The more we learn about dinosaurs, the stranger they become and the more questions we have about their biology. And the mystery of the dinosaur is wrapped up in two complementary themes--how they lived and why almost all of them disappeared. In order to solve those conundrums, we need to solve a slew of other dinosaur mysteries--how they mated, grew up, and communicated with each other through sound, smell, and sight. Of all these puzzles, how dinosaurs came to rule the world is one of the most enduring. Douglass's quarry preserves the heyday of giant dinosaurs--a time when a fantastic array of huge herbivores arched their elegant necks over fern-covered floodplains and tried to avoid an almost equally diverse complement of giant knife-toothed predators. For me, at least, this slice of Jurassic time is the acme of the dinosaur's reign. This is a Jurassic classic. Marvelous as it is, though, the tableau contains a thread we can trace back to the mystery at its source. How did Apatosaurus and its varied kin get their start? How, exactly, did dinosaurs rise to rule the world in such flamboyant fashion? To find out, I have to look elsewhere, and the first stop is a few rock exposures over in the same park. A few miles down Dinosaur National Monument's main drag is a little turnoff for the Sound of Silence Trail--a hike that always puts the Simon and Garfunkel song in a near-endless loop in my head as I walk past the low scrub and sandstone exposures beautifully carved by wind and water. Here, at a little kink in the trail, a deep swath of rust-red rock juts out of the ground in a long curve locally called "the Racetrack." In this section of 220-million-year-old time, among preserved ripple marks and tunnels left behind by ancient worms, are the tracks of svelte, gracile dinosaurs--early members of a dynasty that had not yet come to power. The traces dinosaurs left along muddy lakeshores are all that is here, and even those telltale footprints are rare signs of creatures that were only a marginal part of the prehistoric ecosystem. To understand dinosaur lives, we must examine these Triassic rocks--a time tens of millions of years before Apatosaurus and other dinosaurs stomped and bellowed their superiority. If we are truly going to appreciate dinosaurs for what they are, we have to go back to their humble beginnings. Copyright © 2013 by Brian Switek Excerpted from My Beloved Brontosaurus: On the Road with Old Bones, New Science, and Our Favorite Dinosaurs by Brian Switek All rights reserved by the original copyright owners. Excerpts are provided for display purposes only and may not be reproduced, reprinted or distributed without the written permission of the publisher.