There was nothing modest about the beast named Quetzalcoatlus. This winged creature--the largest flying machine nature ever constructed--was the size of a small airplane. It was nearly 20 ft. long; its wings stretched 40 ft. across; and it boasted a toothless, 6-ft.-long beak that tapered to the width of chopsticks. What on earth, scientists have long wondered, did such a big animal eat?
That was one of the questions researchers tried to answer last week at the annual meeting of the Society of Vertebrate Paleontology in New York City, which featured a symposium focusing on the ancient winged creatures known collectively as pterosaurs. Were flying giants such as Quetzalcoatlus carrion eaters, like outsize vultures, as researchers once proposed? Or were they--as Thomas Lehman, of Texas Tech University, and Wann Langston Jr., of the Texas Memorial Museum, convincingly argued last week--more like humongous storks, probing the lake bottoms for tasty tidbits and snaring them with their lancelike beak?
When dinosaurs ruled the earth, Quetzalcoatlus and its cousins dominated the skies. Yet ever since their fossils were first discovered in the 1700s and mistaken for strange marine creatures or bats, pterosaurs--literally, winged lizards--have remained a perplexing enigma. Did these extraordinary beasts take off by running on the ground or by dropping from a tree? Did they energetically flap their wings or deploy them as passive sails? Did they, like seabirds, nurture their young in large colonies, or did they lead a solitary life?
As last week's meeting made clear, pterosaurs continue to confound. These bizarre animals, the first vertebrates that truly flew, are a "biological oxymoron," says paleontologist Kevin Padian of the University of California, Berkeley. "Apart from the fact that they flew, there isn't a thing that all the experts agree on. How can animals that are so familiar to generations of schoolchildren be so confusing to the people who study them?"
In fact, scientists have learned quite a bit about pterosaurs. For example, they know that the first pterosaurs shared a common ancestor with the dinosaurs and appeared on earth at roughly the same time. The earliest pterosaurs sported long, bony tails that functioned as dynamic stabilizers. By contrast, later models looked more like birds, with their tails shrunken to stubs and their necks and heads greatly elongated. They lacked feathers, but their bodies were probably wrapped in a thick, furlike cloak. The range in size of pterosaurs was enormous. Some were as small and sprightly as robins, while others--like Quetzalcoatlus--were giants five times the size of a whooping crane, the largest bird in North America today.
Like birds, which evolved independently 70 million years later, pterosaurs had bones that were hollow and lightweight. (One scientist refers to pterosaur skeletons as "Styrofoam and mailing tubes.") But of all the trademarks of a pterosaur, one of the most peculiar was its hand, which boasted three clawlike fingers of normal size and a fourth digit that was outlandishly long. It was this fourth finger that provided structural support for the wings. Made of a skin-like membrane, the wings were supported by thousands of microscopic fibers that acted rather like the ribs of a folding umbrella, creating a flexible structure that was stiff enough to be aerodynamic.