The Miracle of Flight

 

Decades ago, one huge discovery by a UT graduate student changed the field of paleontology forever.

The Great Hall of UT’s Texas Memorial Museum is a towering secular temple of limestone blocks and gleaming oxblood marble. Its ground-level display cases are filled with a rotating exhibit of the museum’s treasures, including the skull of a prehistoric steppe bison, a 250-pound amethyst quartz geode, and a 450-million-year-old slab of sedimentary rock studded with beautifully preserved fossils of ancient brittle stars.

But the room is so tall that your natural instinct is to look up, and that’s when you see it: the most famous, the most stirring, the most unfathomable of all the museum’s wonders, the creature whose discovery in 1971 by a University of Texas graduate student startled the world: Quetzalcoatlus.

The Miracle of Flight

The skeleton of the “Texas Pterosaur”—or more precisely, a cast of the skeleton based on fossil remains—hangs suspended from the ceiling high above, almost spanning the cavernous room.  The vertebral column that once supported the animal’s neck appears impossibly long, and the skull at the end of it impossibly longer still, with a flat, bony crest at the top of the head and toothless jaws that form a massive forceps-shaped beak. Its hind legs, with its oddly elegant feet, trail behind. The complicated system of elongated bones and joints that supported its wings measures 40 feet across.

When a living Quetzalcoatlus was on the ground, standing upright on its four legs with its wing membranes folded upward like an umbrella, it was as tall as a giraffe. When it was soaring vulture-like above the late Cretaceous landscape, it was as big as a small jet—the largest flying creature that ever lived.

Pterosaurs were reptiles. They are often referred to as flying dinosaurs, an understandable mistake since that’s pretty much what they look like. But though pterosaurs and dinosaurs shared a common ancestor and inhabited the earth at roughly the same time (from the Triassic period to the end of the Cretaceous, a span of about 140 million years) they belong to a different taxonomic group with a divergent evolutionary history. Neither are they the forbears of the flying animals of our own time, though they once inhabited the same environmental niches that are filled by birds and bats today. More than a hundred different species of pterosaur have been discovered since the first puzzling fossil of a seemingly airborne reptile was found in the late 18th century in the Solnhofen limestone of Germany.  Some species were as small as sparrows, others majestically large.  Some of them energetically flapped their wings in flight, others coasted along on thermals. They were insectivores, carnivores, scavengers. There were species that walked on all fours—leaving behind fossilized trackways that give us an indication of how they moved on the ground—and there were species that perched on branches and cliff sides. Their beaks could be bulbous and dodo-like, or shovel-shaped and crowded with snaggly teeth, or elegantly tapered to a sharp, stabbing point. Some varieties had astonishing crests on top of their heads that scientists have hypothesized served as everything from a mating display to a kind of rudder for maneuvering in flight.

But nobody had any idea just how gigantic a pterosaur could be until the spring of 1971. Douglas A. Lawson, MA ’72, was a 22-year-old graduate student in geology that year. He was doing fieldwork in Big Bend National Park under the supervision of the renowned UT paleontologist Wann Langston. He was by himself most of the time, living alone in a bunkhouse on an old ranch at the edge of the park. Once a week, he would drive into Study Butte or Panther Junction to buy groceries, but the rest of the time he was out in the desert, wandering across the pediment flats and ancient stream beds, searching for fossils and taking geological measurements in a complex outcropping of sedimentary rock known as the Javelina Formation.

The previous fall, with Langston, he had found the frill of a horned dinosaur near Tornillo Flat. Later, as he was climbing up a tricky sandstone ridge, he drove his pick into the rock to keep from falling backward. The pick landed on the jawbone of a tyrannosaurus.

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On the day he found Quetzalcoatlus, he was in the southwestern part of the park, an area where creeks had cut down through the volcanic rubble of the desert floor to expose the underlying Cretaceous rock. He was walking along the dry streambed when he noticed a cluster of dice-sized bone fragments lying at his feet. He knew almost at once, from their color and texture, that they had belonged to some kind of archosaur, the group that includes dinosaurs, pterosaurs, and extinct crocodiles. A hundred yards upstream, he found more bones, lying on the ground and embedded in the sandstone at the top of a 30-foot-high stream bank.

The bones were puzzling, particularly a limb bone solidly cemented in the rock that seemed to be holding up the hillside. The bone was huge, but extremely light and delicate for a dinosaur. Could it belong to a pterosaur? Lawson had trouble believing it could be true. It was way too big. The largest pterosaur known at that time, Pteranodon, was only about half the size that Quetzalcoatlus would later turn out to be.

Nevertheless, Lawson made a notation in his field notes, a preliminary guess that the fossil material could have come from a pterosaur. Then he gathered up all the loose bones and carried them in the desert heat through the cactus and lechugilla to his Jeep. He returned to Austin at the end of the field season and spent a good part of the fall in the Vertebrate Paleontology Lab at UT’s J.J. Pickle Research Campus. He kept staring at one of the fossils he had brought back, a soccer ball-sized clump of sandstone studded with bones.

That was the clincher right there. Once you know it’s a wrist, there’s no other wrist like it. It’s a pterosaur. And it’s huge. It’s gigantic!”

“Okay, what is this thing?” he remembers asking himself one night when he was alone in the lab. That’s when he had his eureka moment. He realized that the bones in the sandstone made up a wrist—a wrist the size of a grapefruit.

“That was the clincher right there. Once you know it’s a wrist, there’s no other wrist like it,” Lawson says. “It’s a pterosaur. And it’s huge. It’s gigantic!”

The next year he went back to Big Bend with Langston to excavate the big embedded fossil he had to leave behind. It was the upper arm bone of the pterosaur, an important piece of the puzzle, but the bones that Lawson found in the creekbed did not make up a whole skeleton. All he had was the left wing. But in 1973, William Amaral, another student of Langston’s who was prospecting in the Javelina Formation, found the bones of much smaller but much more complete pterosaurs. Whether the fossils Amaral discovered belonged to the same species or were merely that of  a very close relation is still a matter of debate, but the new material made it possible to piece together a coherent picture of what the creature had looked like.

Lawson announced the discovery of his pterosaur in a 1975 article in Science. In that pre-Jurassic Park era, when public fascination with paleontology was at a slow burn, he encountered an unexpected micro-burst of celebrity. He was getting ready to give a lecture at UT’s Thompson Conference Center on the paleoecology of the Late Cretaceous in Big Bend when he noticed something strange: reporters and TV crews were lining the walls of the conference room.

“It was a slow news day,” he recalls. “The San Angelo Times changed its lead story from ‘Man Trapped in New York Subway’ to ‘Largest Flying Creature Discovered in Texas.’”

The animal was still unnamed.  Wann Langston warned Lawson that if he didn’t call it something soon, somebody else would.  So Lawson christened it Quetzalcoatlus northropi, after the feathered serpent god of the Aztecs and the pioneer aviation designer John Northrop. “Since it was the biggest flying wing that had ever evolved,” he says,  “I thought I’d name it after the guy that built the biggest flying artificial wing.”

Lawson“This is the thing that Doug found,” Timothy Rowe, the director of UT’s Vertebrate Paleontology Lab (VPL) said on an afternoon this past August as he pulled open a wooden specimen drawer in Langston’s office. Langston had died a few months earlier at the age of 92, but his expansive office still held the charge of his influential personality. There were bones everywhere, an old manual typewriter on the desk, the skull of an Albertosaurus on top of the file cabinet, and on the floor a circa-1960’s “Twist Exerciser,” a square of rotating plywood that looked older than any of the fossils in the room, and whose yellowed label promised “Fun and Exercise for the Whole Family!”

When Rowe pulled out the drawer, I found myself staring at the Quetzalcoatlus humerus, the big upper arm bone that Lawson and Langston had carved out of that Big Bend creek bank in 1972.  It looked like a medieval war club. It was hard to imagine that an animal could have ever gotten off the ground with an arm bone this huge and dense. But Rowe picked up a pterosaur femur from another drawer so I could see the cross-section view of its broken end. The bone itself was exquisitely thin. It encircled a cavity that was filled now with fossilized sediment, but when the Quetzalcoatlus was alive would have been almost hollow.

Rowe pointed out a large bone flare at the end of the humerus. “That’s the delto-pectoral crest. That’s where the shoulder muscle attached. There’s nothing else that has a humerus like this. You never find anything like that except on a pterosaur.”

Rowe allowed me the nerdy thrill of hefting the Quetzalcoatlus arm bone in my own hand. When I set it back down in the tray on top of a paper-clipped sheaf of faded notepaper filled with Langston’s pencil marks, I noticed another bone lying below it. It was substantially more slender than the humerus but at least a foot long, and tapered like a dagger or a railroad spike. This bone was a part—and only a small part—of the giant pterosaur’s amazingly elongated fourth finger, which grew out and out from the hyper-articulated metacarpus, forming a kind of strut that supported the membrane of the creature’s wing.

“Here’s part of the face,” Rowe said, carefully picking up a flattened length of bone eight or nine inches long that I could have spent a lifetime pondering without ever imagining it could have anything to do with anybody’s face. Fortunately, on Langston’s desk there was a partially reconstructed skull of one of the smaller Quetzalcoaltlus specimens that put the puzzling bone into some kind of context, though the skull was unearthly-looking itself—more alien than anything you might expect to see hidden behind a secret door in Area 51. It was long and thin and plow-shaped, with the eyes set—like a toucan’s—far back at the base of the head.

Near the skull stood another curious-looking structure, a tall, wooden frame from which Quetzalcoatlus bones were suspended by string. Langston had used the apparatus, Rowe said, to try out different hypothetical configurations of the animal in flight.

“He was trying to figure out range of movement and that sort of thing.,” Rowe explained. “Also, what was going on with the legs. Did they trail behind like a stork ? Here he’s got them out to the side. Wann was working on this thing steadily for many, many years.”

It pushed the boundaries of what we knew of animals, what life was capable of.”

One of the people who first encountered Quetzalcoatlus here at the VPL was Brian Andres, BS ’00, now an assistant professor in geology at the University of South Florida. Obsessed with paleontology since childhood—“I think I made my career decision when I was about three”—Andres was a freshman at UT when he met Langston in his office. “Here, hold this for a second,” he remembers Langston saying as he handed him a Quetzalcoatlus neck vertebra he was in the process of casting.

“It was truly an amazing experience,” Andres says. Holding a Quetzalcoatlus fossil in his own hands in Langston’s office was part of the chain of inspiration that led him to become a pterosaur expert himself. In fact, when I talked to him in August, he had just published a paper in the Earth and Environmental Science Transactions of the Royal Society of Edinburgh called “Texas Pterosaurs” in which he named a new species, Radiodactylus langstoni, for his late professor.

You can still hear the excitement in Andres’ voice when he talks about Quetzalcoatlus. “You name it, it does it. When it came out it pushed the boundaries of what we knew of animals, what life was capable of. There are papers written going back to the 1800s guessing what the maximum size of flying organisms could be, and Quetzalcoatlus just blew that out of the water. It really pushed the limits of biomechanics in terms of what animals could achieve. Also, pterosaurs are infamously fragmentary, but Quetzalcoatlus is amazingly complete.

“But we’re still trying to figure this thing out, how it lived and breathed. It just boggles your mind. Here was an animal that could look a giraffe in the eye, then take off and fly.”

Pterosaur_silhouette

Exactly how it took off and flew is a matter of lively scientific conjecture.  It was a very large animal—Andres’ best guess is a minimum wingspan of slightly more than 32 feet—and it’s harder for very large animals to get themselves into the air. To become airborne, it probably ran along on all four legs until it reached something close to take-off speed, then shoved itself upward with its front feet, gaining just enough altitude for a propulsive downward stroke of its wings to launch it into flight.

Once in the air, it probably flew with a minimum of wing flapping, gliding along on air currents and thermals. Many pterosaur species lived exclusively on coastlines. So far Quetzalcoatlus has been found only in inland environments, so it’s likely it wasn’t limited to coastal regions. It may have traveled long distances to ancestral nesting sites, just like many migratory birds do today. Nobody knows for sure what the creatures ate, or how exactly they ate it, but Andres thinks that a useful modern equivalent for understanding the diet of Quetzalcoatlus might be the Marabou stork of Subsaharan Africa, which is an active hunter of fish and amphibians and small mammals, as well as a canny scavenger that looks for meals where vultures congregate.  Oh, and one other thing: Quetzalcoatlus was, in Andres’ words, “fluffy.” Its body would have been covered with a mat of bristles that a human eye—had there been a human eye back then—would have registered as hair.

A cuddly, flying furball is not the first thing that comes to mind as you stare up at the giant skeleton hanging from the ceiling of the Texas Memorial Museum. But Quetzalcoatlus has a way of testing the human imagination in general. Forty-two years after Doug Lawson came across its bones in Big Bend, the creature remains a landmark scientific discovery and a crucial inspiration for young paleontologists like Andres.

It also remains a mystery. Standing below the giant skeleton in the Great Hall, you can’t help but wonder: Could this possibly be true? Did something like this really once live on our own earth?  If so, what would it have been like to be alive back then to witness it?  The first clue might have been a slight darkening of the sky, or the sound of raucous chattering—perhaps squawking, honking, or reptilian hisses.. Your attention drawn upward by the disturbance, you would have raised your eyes and seen wave after wave of giant migrating pterosaurs blocking out the sun, their wing beats making a sound like great sails filling with wind as they flew, their long necks extended and their keen eyes scanning the ground, through the Mesozoic skies.

Stephen Harrigan is a faculty fellow at UT’s Michener Center for Writers.

From top, illustration by Marc Burckhardt; an article from the New York Times in 1975 puts the giant pterosaur in perspective; Lawson with the giant pterosaur limb bone he found in Big Bend in 1971. Courtesy Jackson School of Geosciences; the cast of a Quetzalcoatlus that hangs in the Great Hall of UT’s Texas Memorial Museum. Courtesy Jackson School of Geosciences.

 

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