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Stories of Mysterious Tunnels and Subterranean Cities. Watching coastal birds helps Padian envision the time when pterosaurs occupied the same ecological niche, plunging for fish like pelicans, soaring like gulls, and pecking at the sand like sandpipers. They did it long before birds and bats. And it terms of size, they pushed the envelope as far as it could go for a flying animal. Like their cousins the dinosaurs, pterosaurs stand out as one of evolution's great success stories. They first appeared during the Triassic period, million years ago, and thrived for million years before going extinct at the end of the Cretaceous period.
Their endurance record is almost inconceivable compared with the span of humans, whose ancestors started walking upright less than four million years ago.
Uncontested in the air, pterosaurs colonized all continents and evolved a vast array of shapes and sizes. Of more than named species, the smallest pterosaur measured no bigger than a sparrow; the largest reached a wingspan of nearly 40 feet 12 meters , wider than an F fighter.
Until recently most paleontologists would not have put pterosaurs in the same league as birds in terms of flying ability. Because pterosaurs were reptiles, generations of scientists imagined that these creatures must have been cold-blooded, like modern snakes and lizards, making them awkward aerialists at best. In the past three decades, however, a surge of fossil discoveries around the globe has prompted researchers to reexamine their views.
The emerging picture of pterosaurs reveals that they were unlike any modern reptile. From a fossil discovered in Kazakhstan, paleontologists suspect that pterosaurs had a hairlike covering, perhaps akin to fur. If so, this detail provides evidence of a high-revving, warm-blooded physiology that could sustain the kind of exertion needed to stay in the air.
Judging from the skulls of other fossils, scientists reason that many pterosaurs were gifted air-borne predators, built to feed on the wing. They darted after insects, dive-bombed for fish, and soared hundreds of miles over open ocean on extended hunting expeditions.
People had the idea that pterosaurs could glide, but they couldn't flap their wings," explains Alexander Kellner, a Brazilian paleontologist. Pterosaurs first grabbed Kellner's attention when he was a child in Rio de Janeiro, where he became hooked on a television cartoon featuring one. His early fascination might have foundered, but when Kellner was a student, Brazilian scientists started to uncover a mother lode of pterosaur fossils in the northeastern part of the country, on the slopes of the Araripe Plateau.
In the past 30 years Araripe has yielded remains of 19 new species, an unrivaled pace of discovery. These pterosaurs soared over South America during the middle of the Cretaceous period, more than a hundred million years ago. At that time a large saltwater lagoon covered the Araripe area, and the African continent lay just over the horizon, separated by a young sliver of ocean that would later grow into the Atlantic. Among the Araripe discoveries some of the strangest have been identified by Kellner and his mentor Diogenes Campos of the Brazilian Department of Mineral Production.
At his office in Rio de Janeiro, Campos pulled out one of his favorite characters, a million-year-old Araripe pterosaur that he and Kellner christened Anhanguera, or "old devil. Still partly entombed in rock, the glossy fossil looked leaden and cold. But as I ran my fingers over the inch-long centimeter-long jawbone, tracing its curves and pits, I could imagine the Araripe pterosaurs sailing over the ancient lagoon. A solitary Anganguera takes flight, its foot 4-meter wingspan silhouetted against the sky.
The pterosaur sweeps its large keen eyes over the water, pulls its wings inward to pick up speed, and swoops low. Dropping its mouth into the water, the hunter uses its beak to slice through the waves like a black skimmer bird.
In a flash the pterosaur jerks its head up and veers skyward, gripping a wriggling fish in its teeth. Along the shore diminutive pterosaurs called Tapejara wellnhoferi pluck nuts and fruit from scrubby trees with their toucan-like beaks. Above the whole tableau soars the most impressive Araripe species, a giant called Tupuxuara, with a foot 6-meter wingspan. This toothless pterosaur had a rounded four-foot-long 1. Paleontologists can paint this vivid portrait of Araripe pterosaurs because their bones were exquisitely fossilized, intact and uncrushed, within the quiet sediments at the bottom of the lagoon.
By comparison, the flattened pterosaurs from most other sites around the world look like prehistoric roadkill. The Araripe fossils have enabled researchers to get a better fix on what pterosaurs actually looked like and how their bones fit together. They can see, for example, how the upper arm bone, or humerus, produced the flapping motion that kept pterosaurs in the air. The bone looks something like a hatchet: a stout shaft topped by a flared-out blade where it joined the shoulder.
The wide head must have provided a broad anchoring point for the powerful chest muscles pterosaurs needed to flap their wings. The weight of these large muscles was offset by lightweight, eggshell-thin bones filled with air. Larger species had slender struts inside hollow wing bones, adding strength without many additional pounds.
So even with wings almost as wide as a house Tupuxuara may have weighed no more than a child. Hollow bones gave pterosaurs an advantage during life but were a hindrance to their immortality. Pterosaur skeletons were so delicate that they survived as fossils only when their corpses came to rest in a protected environment. For that reason most pterosaur remains come from species that lived near the ocean—the soft seafloor ooze entombed their bodies for eternity.
Even with the new discoveries, the rarity of fossils leaves major gaps in knowledge about pterosaurs. No one knows how they evolved flight, why they vanished, or exactly what they looked like. Debate swirls around these reptiles like the air currents they once rode. Controversy has surrounded pterosaurs since the first discovery of one at the end of the 18th century. At the Bavarian State Collection of Paleontology and Historical Geology in Munich, paleontologist Peter Wellnhofer pulled out a large drawer filled with fossils and pointed out a fragile skeleton, which was no bigger than my hand.
Embedded in a slab of limestone million years old, the creature lay with its mouth agape in a pose of prehistoric horror. It has a long toothy snout, a giraffe-like neck, and lanky legs, but its most unusual feature is its forelimbs.
Next to three small fingers is a fourth that extends ten times the length of the other digits. Cosimo Alessandro Collini, the first natural historian to study the fossil, was stumped when he described it in Seventeen years later the great French anatomist Georges Cuvier deduced that the animal was a flying reptile, whose fourth finger supported a wing. Although the wing surface had not fossilized, Cuvier surmised that a membrane of skin had attached to the forelimb in life.
He later named the fossil Pterodactylus, combining the Greek words for wing and finger. A few decades later the term pterosaur, or winged reptile, was coined to describe the growing list of similar fossils. In a remarkable pterosaur specimen came to light that confirmed Cuvier's deduction. Unlike earlier fossils, this new find near the Bavarian town of Solnhofen contained delicate wing impressions, clear proof that extinct reptiles could fly.
Even with more than a thousand pterosaur specimens known today, such wing impressions remain rare. Normally only bones survive the fossilization process. Material as ephemeral as skin or hair disintegrates long before an animal turns to stone. But time was kind to the pterosaurs that died near Solnhofen because many were preserved in the sediments of a Jurassic lagoon.
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