My Beloved Brontosaurus

by Brian Switek

  Now, every Archaeopteryx specimen ever found—from a single isolated feather used to establish the creature’s name in 1861 to the eleventh specimen announced in 2011—has come from southern Germany. The one I was going to see was one of the more recent discoveries, but we’ll get to that in a moment. All the Archaeopteryx skeletons are preserved in limestone slabs that record the Jurassic life that sank to the bottom of an ancient sea that covered much of Europe around 150 million years ago. Crustaceans, fish, pterosaurs, small dinosaurs, and other creatures have all turned up in quarries, but the most cherished of all the fossils are those of Archaeopteryx lithographica. The high-definition preservation of these fossils not only recorded the anatomy of the creature’s bones, but, in many of the specimens, vestiges of the feathers, too. That’s what made the first Archaeopteryx skeleton ever found such a sensation.

  Known as the “London specimen,” the animal resembled certain dinosaurs in terms of its anatomy, yet Archaeopteryx clearly had feathers. Freshly embroiled in the controversy stirred by Charles Darwin’s On the Origin of Species in 1859, Victorian evolutionists privately rejoiced that the creature was a confirmation that transformations from one kind of creature to another were actually possible. As the paleontologist Hugh Falconer called it, in a private letter, Archaeopteryx was a “strange being à la Darwin,” and Richard Owen (who obtained the first skeletal specimen for what is now London’s Natural History Museum) deemed Archaeopteryx to be the “by-fossil-remains-oldest-known feathered Vertebrate” and the earliest known bird.

  Owen’s ambitious plans for his museum were what brought Archaeopteryx to England. He wanted unique, dazzling fossils for his collection, and convinced the museum to front the cash for the German fossil. Once everyone understood how important the early bird was German paleontologists were sore that their country’s prize fossil had been so easily acquired by foreign scientists. While the second Archaeopteryx skeleton—called the “Berlin specimen,” the most beautiful fossil of all time—was almost sold overseas to O. C. Marsh at Yale, and the cryptic Haarlem specimen—confused for a pterosaur until 1970—is held at the Teyler Museum in the Netherlands, all but two Archaeopteryx stayed in Germany. If you see an Archaeopteryx in an American museum, chances are that you’re looking at a cast … unless you’re in the middle of Wyoming.

  Going by appearances alone, you’d never guess that Thermopolis contained anything as important as an Archaeopteryx. Faded signs along the highway leading to the isolated town give equal billing to the Wyoming Dinosaur Center and the “Safari Room”—a dining room decorated by the stuffed spoils of a big game hunter at the town’s overpriced Days Inn. You know you’re getting close to the local dinosaur showroom when you spot a metal Allosaurus skeleton on a street corner along the main drag, frozen as if roaring at the cars passing by.

  I follow the suburban streets to the gravel parking lot outside the museum, anxious to get out of the sun and into the cool building where the famous fossil rests. The exterior of the Wyoming Dinosaur Center is as mundane as the drab dinosaurs I met in elementary school. There are no windows, columns, statues, or, really, much of anything. The gray building displays “Wyoming Dinosaur Center” in mismatched shades of green, and the whole structure baked in the heat of the August afternoon. I pay my ten-dollar entry fee and am directed by a disaffected young woman to a corridor that will lead me through the exhibits.

  Contrary to its title, the Wyoming Dinosaur Center displays a variety of other forms of prehistoric life. The dinosaurs are the real draws, of course, and keep people moving along the hallway, past the petrified invertebrates and fossil fish. Along the way, I notice one large slab to the left of the path, depicting an aggregation of pancake-size ancient horseshoe-crab-like arthropods called trilobites; a nearby shelf displays a reproduction of the wormlike, schnozzle-faced invertebrate called a Tully monster (once a contender for the identity of the Loch Ness Monster, in fact); and a small alcove presents an array of early tetrapods, the amphibious vertebrates that were the first to clamber onto land around 375 million years ago. And then there are the dinosaurs. Some of the fossils on display are authentic. Others are casts, which isn’t too surprising, given how difficult it is to put together heavy, invaluable bones of prehistoric creatures.

  I didn’t come for fiberglass dinosaurs. What I had driven all morning to see was the real thing, and there it was. Set behind a protective pane of glass, the Thermopolis Archaeopteryx rests in its limestone tomb. The skeleton, about the size of a raven’s, was preserved in an odd pose, presenting the dinosaur as though it had fallen backwards off a bicycle—legs splayed, head thrown back, arms to the side, and all surrounded by the faint impressions of feathers. The little dinosaur’s skeleton resembles the fierce anatomy of Velociraptor, but the array of feathers gives the Archaeopteryx fossil a subtly different character. I stand and stare at the fossil for a while, tracing its form along the slender toes and thin legs up the contorted spinal column to the animal’s wishbone, still situated between the birdlike shoulders. A heavyset man and his towheaded son, both decked out in the logos of their favorite sports teams, slowly amble past and don’t pay the little slab much attention. The dramatic scene of a skeletal Monolophosaurus sinking its recurved teeth into the side of a long-necked Bellusaurus is apparently far more interesting and consistent with the character of the “terrible lizards.”

  They have no idea what they are missing! As I daydream about the bones, I wonder how this fossil wound up in such an isolated little town. Outside of Germany, I would have expected such a fossil to be on display in one of the venerated institutions further east—Chicago’s Field Museum, the American Museum of Natural History in New York City, or Pittsburgh’s Carnegie Museum of Natural History. What the hell was Archaeopteryx doing here?

  It turns out that no one knows when this specimen was originally collected or where it was found. Rumor has it that the fossil was discovered some time in the 1970s, and the specimen was effectively a private secret until 2001, when a Swiss collector’s widow offered it for purchase to Germany’s Senckenberg Museum in Frankfurt. The museum declined, but in 2005 Burkhard Pohl of the Wyoming Dinosaur Center arranged a deal whereby the Archaeopteryx would be on long-term loan to the private museum. And even though fossils receive some protection in most federal states of Germany under Monument Protection Acts, Bavaria (where the Archaeopteryx fossils are found) doesn’t have such a law, and so the export of the Archaeopteryx to Switzerland, and later to the United States, was perfectly legal, no matter how painful it was to see the specimen wind up at a commercial institution far from home. Too many countries have been robbed of their prehistoric heritage thanks to lax fossil regulations.

  Had I visited the museum a day earlier, I wouldn’t have given a second thought to what I was looking at. I would have taken it as current fact that, as it had been regarded for a century and a half, Archaeopteryx was the key to bird origins. Whether or not Archaeopteryx was a direct ancestor of later birds didn’t matter—as the earliest bird, the feathered dinosaur represented the form of the very first avians. But now I had to wonder about the nature of the creature. Was the Archaeopteryx behind the glass truly an early bird, or a different kind of dinosaur simply hiding behind beautiful plumage?

  I also knew that Archaeopteryx has always had a controversial place in our developing understanding of how birds evolved. Even around the time the fossil was originally discovered, and Richard Owen asserted that the bird lineage started with such a creature, other naturalists were not so sure. Darwin’s friend and vociferous defender Thomas Henry Huxley sidelined Archaeopteryx as a weird animal that was almost entirely irrelevant to the question of bird origins. Instead, an influence on the evolutionary circumlocutions of German biologist Ernst Haeckel, Huxley proposed that the origin of modern birds went through a three-step process, starting with creatures similar to the small dinosaur Compsognathus, a diminutive theropod found in the same deposits as Archaeopteryx. “There is no evidence that Compsognathus po
ssessed feathers; but, if it did, it would be hard indeed to say whether it should be called a reptilian bird or an avian reptile,” Huxley wrote.

  Contrary to what has so often been claimed on his behalf, Huxley didn’t suggest that birds evolved directly from any known dinosaur, but proposed that something in the general form of Compsognathus was adapted into a flightless bird akin to an ostrich or an emu, and that these birds were the ancestors of flying birds. Archaeopteryx was just an evolutionary sideshow that illustrated that birds could possess reptilian traits, but did not fit anywhere into Huxley’s scheme.

  True to the often contentious nature of science, not everyone agreed with Huxley’s proposal. Paleontologists such as Samuel Williston, Franz Nopsca, and O. C. Marsh hypothesized that birds really did have a direct dinosaurian origin. Exactly which dinosaurs was the real matter of debate. Some authorities favored the small, generally birdlike theropod dinosaurs, while others suggested that ornithischian dinosaurs such as Hypsilophodon—on the basis of their birdlike hips—were the true ancestors of birds. Still other naturalists mixed and matched these ideas. Perhaps some birds evolved from one dinosaur group, while the rest were derived from the other. Then again, Richard Owen and Harry Govier Seeley insisted that birds had evolved from pterosaurs, a different kind of archosaur that flew thanks to membranes stretched over an elongated finger. Huxley and other naturalists disputed this—the characteristics that united birds and pterosaurs were instances of convergence related to a similar lifestyle—but no one knew for certain exactly how birds evolved. And, despite Huxley’s difference of opinion, Archaeopteryx became the singular touchstone for understanding the transition from reptile to bird. Any theory of bird origins had to take Archaeopteryx into account.

  Even as paleontologists agreed that Archaeopteryx was the earliest bird, though, they were left with the question of what sort of reptile it had evolved from. The Scottish paleontologist Robert Broom suggested a solution in 1913 that made sense of the traits shared by dinosaurs, pterosaurs, Archaeopteryx, and other birds. Before the era of the pterosaurs and dinosaurs, during the earliest parts of the Triassic, the crocodile-like archosaurs ruled. One of these creatures, Euparkeria, was a bipedal, carnivorous croc relative that was old enough and generalized enough that it could be a common ancestor for dinosaurs, pterosaurs, and birds. If all three lineages evolved from such a creature—a common and relatively unspecialized rootstock—then that would explain why they were so perplexingly similar to each other.

  It wasn’t until an early-twentieth-century artist took up the question of bird origins that the answer was considered settled. Gerhard Heilmann was an accomplished illustrator as well as an amateur paleontologist, and in 1926 he published an English translation of a series of articles he had written in Danish called The Origin of Birds. I was fortunate enough to track down a copy a few years ago, and the book is a real treasure. The glossy pages are filled with detailed comparative drawings of bird and dinosaur skeletons, and Heilmann illustrated a few dinosaurs in active poses, such as a pair of Iguanodon sprinting over the Cretaceous plains. Heilmann’s scientific argument was just as elegant as his drawings. Even though he acknowledged that some dinosaurs were birdlike, there was one feature that in his view barred dinosaurs from bird ancestry. Or rather, it was the lack of a feature. Heilmann knew that birds have a wishbone, or the modified set of clavicles known as a furcula. As far as Heilmann knew, no dinosaur had ever been found with these bones. Dinosaurs had apparently lost their clavicles during the course of evolution, and since a feature couldn’t re-evolve once it had been lost, Heilmann reasoned, there was no way that dinosaurs could be ancestors of birds. The next closest group that had clavicles contained Euparkeria and its croc-like kin, and so Heilmann concluded that birds and dinosaurs had so many features in common because they had evolved from a common ancestor.

  Paleontologists found Heilmann’s argument very persuasive—so much so that they overlooked the fact that dinosaurs did indeed have clavicles! A wishbone can clearly be seen in a diagram of bones published with the description of the beaked theropod Oviraptor in 1924, and a wishbone was found among the bones of the small theropod dinosaur Segisaurus, described in 1936 from a skeleton found crouched in a birdlike, roosting position. Heilmann’s hypothesis had become so entrenched that paleontologists somehow missed even seeing these clavicles, and the idea that birds and dinosaurs independently evolved from a common, crocodile-like ancestor remained in favor—until a sharp-clawed dinosaur cut through the debate.

  In 1969, the Yale paleontologist John Ostrom named Deinonychus antirrhopus from a quarry full of partial skeletons in Montana. With grasping hands, a long, still tail, and, most remarkable of all, a hyperextendable toe capable of plunging the dinosaur’s “terrible claw” into prey, this dinosaur was clearly an agile and active predator. Deinonychus seemed as different as could be from the traditional vision of idiotic, swamp-bound dinosaurs—like the ones Ostrom himself had helped design for the Sinclair pavilion of the 1964 World’s Fair—but the osteology of this dinosaur was not totally unprecedented. Deinonychus was very birdlike, and Ostrom quickly recognized the similarity between his newfound predator and Archaeopteryx. The dinosaurian origin of birds had clawed its way back into the scientific spotlight.

  * * *

  The idea that birds are dinosaur descendants changed our entire perception of what dinosaurs were. If modern birds are dinosaurs, and dinosaurs resembled avians, then long-held assumptions about dinosaur biology had to be wrong. Maybe not all dinosaurs hopped around like magpies or ran with the grace of an ostrich, but the links between Archaeopteryx and Deinonychus hinted that some bird traits—such as highly active metabolisms, warm body temperatures, and even feathers—originated deep within the dinosaur family tree.

  A 1975 article by Bob Bakker, one of Ostrom’s students and the guy who catalyzed the Dinosaur Renaissance, included a restoration of the Triassic dinosaur “Syntarsus” with feather-like scales and a crest of plumage on its head as a speculative tribute to the revamped avian dinosaur hypothesis. And, Bakker noted, such a view generated “a particularly happy implication” for dinosaur fans: “the dinosaurs are not extinct; the colorful and successful diversity of the living birds is a continuing expression of basic dinosaur biology.”

  Ostrom’s and Bakker’s ideas filtered through to the documentaries I eagerly watched in my youth. One of my favorite shows was The Dinosaurs! on PBS. (Documentaries about the prehistoric celebrities in the late 1980s and early ’90s regularly combined the word “dinosaur” with whatever number of exclamation points was desired to make their point, from Dinosaur! to The Dinosaurs! and the extra-emphatic Dinosaurs! Dinosaurs! Dinosaurs!) One Thanksgiving Day, PBS ran the entire four-part series in a dinosaur marathon, giving me hours of prehistory-fueled joy while the traditional holiday dinosaur, dressed and stuffed, was downstairs in the oven. In one episode, which highlighted the essential connection between dinosaurs and birds, a little green dinosaur—Compsogntathus, I presumed—ran through an ancient forest. As the chicken-legged beast climbed up a log, though, it quickly sprouted feathers and took on more of a confident strut, all before leaping into the air and metamorphosing into a modern pelican.

  An episode of PBS’s series The Infinite Voyage included a little more detail. A very fluffy Deinonychus went transparent, showing key bones in the skull, arms, hips, and legs, and as the dinosaur ran it transformed into an Archaeopteryx and, ultimately, took flight as a crane. On the outside, a modern bird and something like Deinonychus might seem drastically different, but when you look at their skeletal framework, the differences aren’t so extreme, after all.

  Despite all this conditioning, I still thought feathered dinosaurs looked silly. Dinosaurs were supposed to look mean and scabrous. With feathers on, Velociraptor just looked like a big chicken. Plush, downy dinosaurs in gift shops did nothing for me. They looked far too cuddly to be adept flesh-renders. Jurassic Park entrenched visions of olive-green, scaly carnivores in my you
ng mind, and even now, there are some absolutely daffy feathered dinosaurs that I feel downright embarrassed for. One of the worst models is on display in Las Vegas—a Deinonychus plastered with feathers, creating what I can only imagine is some Cretaceous version of Robert Smith from The Cure. Mounts like this one may do more harm than good in communicating our new image of dinosaurs—a vision in which scaly hides have given way to feathery ones. Like it or not, many dinosaurs were fuzzy, fluffy, and feathery.

  Feathers have a very deep evolutionary history. Their trail goes much deeper than the earliest birds, and may even go back as far as the first dinosaurs. Indeed, a flood of fossils discovered over the past fifteen years have irrefutably shown that most, if not all, dinosaur lineages had some kind of feather-like body covering.

  The first fluffy dinosaur discovery enthralled paleontologists. At the annual Society of Vertebrate Paleontology conference in 1996, scientists circulated a photograph of a small fossil that revealed a mane of fuzz along a dinosaur’s back and tail. John Ostrom, who was chiefly responsible for reinvigorating the idea that birds are dinosaurs, was “in a state of shock” after hearing the news. At long last, a feathery non-avian dinosaur had really been found. This creature, labeled Sinosauropteryx in a technical publication the same year, didn’t have feathers suited for flying. The simple dinofuzz covering the creature’s body could only have been for display and insulation—the dinosaur lacked the specialized, asymmetrical feathers that allow modern birds to take to the air. In fact, it would have looked very much like Huxley’s hypothetical feathery Compsognathus. The newfound dinosaur pointed to the hypothesis that feathers were not originally used for flight, but had evolved for different reasons and were later co-opted.