• That Killer Instinct
North America and Australia were both menageries of gi- ant vertebrates—until human hunters arrived. Mastodons, woolly mammoths, ground sloths, giant armadillos, and saber-toothed tigers roamed North America 14,000 years ago. Yet within 1,000 years after people showed up, all of these large mammals disappeared. Likewise, before humans arrived in Australia 50,000 years ago, the outback was home to 660-pound claw-footed kangaroos, giant wombats, and the 220-pound flightless Genyornis, the heaviest bird ever known. Some 4,000 years later, the creatures were extinct.
Two studies published this past spring pin the blame squarely on humans. John Alroy of the University of California at Santa Barbara designed a computer model to simulate the actions of "virtual hunters" and found that the arrival of humans in North America correlated with the demise of some 30 species of giant fauna. Geochronologist Richard Roberts of the University of Melbourne used a sophisticated optical technique to date megafauna-filled sediments from 28 sites across Australia. He discovered that 55 different vertebrate species vanished just as humans were dispersing across the continent.
Some scientists have blamed a lethal virus or climate change for the annihilation of giant vertebrates in America. But Alroy says there is no virus that could kill mammoths but spare rodents and rabbits. And although the environment at the time was warming all over the world, the eradication of large mammals was confined to the American continent.
— Josie Glausiusz
|Hadrocodium wui's tiny skull reveals three middle-ear bones and a single jawbone—characteristics it shares with modern mammals.|
Photograph courtesy of Carnegie Museum of Natural History.
When Wu Xiao Chun, A Reptile Paleontologist, Found the dime-sized fossil in 1985 in the Lufeng Basin of southwestern China, he thought it was a fragment of a lizardlike creature. But when he started chipping away at the minute specimen three years later, Wu was surprised to discover that the rock encased a complete skull. More than a decade of tests revealed that the skull belonged to a tiny shrewlike creature that weighed no more than a paper clip but scurried amid Jurassic-era dinosaurs 195 million years ago. In May a team of Chinese and American researchers made a surprising announcement: The fossil may be the remains of the oldest known ancestor of mammals.
The new species, Hadrocodium wui, had a precociously large brain and the middle ear typical of modern mammals. "These are the vital distinctions between mammals and nonmammalian vertebrates, but it has been a challenge for scientists to trace the origins of these features in the fossil record," says Zhe-Xi Luo, a vertebrate paleontologist at Pittsburgh's Carnegie Museum of Natural History. Previously, these characteristics were found only in mammals dating to about 150 million years ago. "The Hadrocodium dates to the early Jurassic, some 45 million years earlier," Luo says. With its enlarged brain and tiny body, Hadrocodium most likely had great energy requirements. "It probably ate very small insects and small worms, and it would have had to eat continuously because of its high metabolism rate," Luo says. Having a big brain didn't mean, however, that Hadrocodium was particularly bright. Says Luo: "Mammals, even tiny ones, need big brains just to coordinate all their bodily systems."
— Curtis Rist
• The Proof Is in the Plumage
|The duck-sized, fleet-footed dromaeosaur sports sharp claws, a long reptilian tail, and lots of downy feathers.|
Photographs courtesy of Mick Ellison/Museum of Natural History
Liaoning Province in northeastern China has been the focal point in recent years of a great treasure hunt: the quest to find the missing evolutionary link between dinosaurs and birds. Volcanic eruptions in the area more than 120 million years ago buried a wide variety of creatures in fine ash, which helped neatly preserve their fossilized remains. One Liaoning specimen, heralded during the 1990s, turned out to be a hoax, a composite of bones and featherlike imprints pieced together by an enterprising Chinese farmer. But last April a research team led by Qiang Ji, a paleontologist with the Chinese Academy of Geological Sciences, and Mark Norell, chairman of the division of paleontology at the American Museum of Natural History in New York City, announced that they had found the real thing: a feather-covered dinosaur embedded between two fine-grained slabs of rock.
The creature is a 130-million-year-old dromaeosaur, a fast-moving, meat-eating theropod related to Velociraptor. What makes the fossil so remarkable, says Norell, is the preservation of such fine details as the feather attachments to the skin, a rarity among fossils. The skeleton, which measures two feet from its head to the tip of its tail, is literally haloed with fibers and filaments. "This fossil radically modifies our vision of these extinct animals," says Norell. "It shows us that advanced theropod dinosaurs may have looked more like weird birds than giant lizards." So why did the flightless creatures have feathers? Norell speculates that dinosaurs may have sprouted feathers at the same time they developed warm-bloodedness. "Smaller dinosaurs like this one, and perhaps the young of larger species like Tyrannosaurus rex, may have needed featherlike body coverings to maintain their body temperature," he says. Thus dinosaurs may have been the first creatures to enjoy the warmth of fluffy down.
— Curtis Rist
• Rock and Roll Dino
|This one-inch-long front tooth of Masiakasaurus knopfleri is better suited to stabbing than to slicing.|
Photograph courtesy of Scott Sampson/Utah Museum of Natural History
While digging for dinosaur bones in Madagascar, a team led by Scott Sampson of the University of Utah endured 100-degree days with no access to showers. But one modern amenity in their camp helped them forget the heat as they scraped stony soil in search of fossils—a portable stereo that pumped out rock and roll. Which led to a strange coincidence: Every time the Brothers in Arms
album by Dire Straits played, more and more bones of a dinosaur from the late Cretaceous Period appeared. "It became our running joke," says Sampson. "If we didn't play it, we wouldn't find the fossils, and if we did play it, we would."
Last January, Sampson and his colleagues unveiled the results of their stereo adventure, a two-legged predator about six feet long and three feet tall that weighed about 80 pounds. It had front teeth that pointed nearly straight out of its jaw. "These teeth are unique among dinosaurs discovered so far, and they show us that we still have much to learn about the diversity of these great animals," Sampson says. Looking for analogies among living creatures, the closest he could discover were shrews, which use their front teeth to stab prey. "This dinosaur would probably have done the same and would have been an especially vicious predator."
Sampson dubbed the creature Masiakasaurus knopfleri, which means "vicious lizard of Knopfler," in honor of a man who had been an unwitting inspiration to everyone at the dig: Mark Knopfler, the lead singer of Dire Straits. When Knopfler, 51, learned of the unusual accolade, he said, "The fact that it's a dinosaur is certainly apt, but I'm happy to report that I'm not in the least bit vicious."
— Curtis Rist
• On Golden Pond
|A Chinese trove of ancient salamanders includes fossil impressions of juveniles (top) and an adult skeleton (below).|
Photographs courtesy of Mick Ellison/University of Chicago
A lake or a pond, Henry David Thoreau once observed, "is earth's eye; looking into which the beholder measures the depth of his own nature." A pond in China that lay buried under volcanic ash for more than 150 million years has proved to be just such an eye on the wonders of evolution. The pond contained more than 500 complete skeletons of a creature that has fascinated intrepid pre-adolescent naturalists since time immemorial: the salamander. "Except for small bones, these look exactly like salamanders that you might find in your yard," says Ke-Qin Gao of the American Museum of Natural History in New York City. The discovery by Gao and Neil Shubin, a professor of biology and anatomy at the University of Chicago, not only put the origins of modern salamanders back 50 million years earlier than believed but also revealed that all 10 living families of salamanders originated in Asia before spreading to North America and Europe. "This is the Pompeii of salamanders," says Robert Carroll, a zoology professor at McGill University who has studied the specimens. "In our dreams no one could have hoped for a fossil record quite like this one."— Curtis Rist
• Frozen Leftovers
As researchers battled frostbite in Siberia to unearth a woolly mammoth last May, they began to question how a creature that weighed more than 12,000 pounds could have satisfied its appetite in such a forbidding landscape. "It's hard to imagine a mammoth living in a tundra," says lead researcher Dick Mol. So he and Jan Peter Pals, a paleoecologist at the University of Amsterdam, decided to find out what was on the menu when the mammoth they called Fishhook had its last meal 20,000 years ago. Working in an ice cave, they extracted the contents of Fishhook's stomach and discovered grasses, pollens, insects, and algae. The findings suggest that the mammoth grazed on relatively lush steppe vegetation. Soon Mol and Pals will look into Fishhook's intestines for even more clues. — Diane Martindale
• A Giant Among Dinosaurs
|Field researcher Matthew Lamanna helps excavate Paralititan stromeri's left humerus, which weighs 400 pounds.|
Photograph courtesy of Josh B. Smith/University of Pennsylvania
Josh Smith had one goal when he set out to become a paleontologist: "I wanted to find something big that everyone else had overlooked." Last June, Smith announced he had unearthed the bones of the second largest creature known to have walked the Earth, a dinosaur that would have dwarfed four elephants standing on top of one another. The lumbering herbivore measured 80 to 100 feet long, weighed as much as 150,000 pounds, and 94 million years ago foraged in Egypt's BaharÏya Oasis, an area 160 miles southwest of Cairo. Baharõøya is now part of the Sahara Desert but was mangrove swampland during the late Cretaceous Period.
Smith dubbed his titanosaurid Paralititan stromeri. Paralititan means "tidal giant," and stromeri honors Ernst Stromer von Reichenbach, a Bavarian geologist who found four new dinosaur species in Baharõøya between 1915 and 1936. Allied bombers leveled a Munich museum in 1944 that housed the fossils and notes from Stromer's expeditions. Meanwhile, the dinosaur quarries he discovered disappeared under the swirling sands of the Sahara. For more than half a century, the Baharõøya Oasis attracted few fossil hunters. While drinking beer one night with his fellow grad students at the University of Pennsylvania, Smith decided to search for the old sites: "It sort of had the feel of an Indiana Jones adventure."
On a subsequent trip to Egypt, Smith set out across the desert in a Toyota Land Cruiser with friends. Smith was armed with geographic coordinates for an old Stromer quarry that happened to be wrong, so he was soon lost."We headed for an outcropping that looked interesting," he says, "and I stuck my head out the window just to see if I could spot anything." That's when he noticed a darkish lump protruding from the sands. "I said, 'Whoa!' Bones have a fractured look about them that rocks never do. And this was a bone for sure."
The lump turned out to be part of the forearm of Paralititan stromeri. Later, Smith and a team of researchers recovered about 20 percent of the creature's skeleton. Argentinosaurus, another titanosaurid discovered in South America in 1993, is the only known dinosaur of comparable size; it was roughly the same length as Paralititan but weighed 60,000 pounds more. Still, Smith remains modest about his success: "Paleontology is just a lot of guess-work and a lot of blind luck. It's nothing more complicated than that."
— Curtis Rist