Paleontology news

Karl Bates and his colleagues in the palaeontology and biomechanics research group have reconstructed the bodies of five dinosaurs, two T. rex (Stan at the Manchester Museum and the Museum of the Rockies cast MOR555), an Acrocanthosaurus atokensis, a Strutiomimum sedens and an Edmontosaurus annectens.

Acrocanthosaurus atokensis was a large predatory dinosaur that looked like T. rex but with large spines on its back and roamed the earth much earlier in the mid Cretaceous period, around 110M years ago. The team suggest Acrocanthosaurus probably weighed in at a similar mass to MOR555 and other medium sized adult T. rex at about 6 tonnes.

The Strutiomimum sedens, whose name means “ostrich mimic”, lived alongside T. rex in the late Cretaceous period and probably weighed somewhere between 0.4 – 0.6 tonnes

The reconstruction of Edmontosaurus annectens, a plant-eating hadrosaur was based on a juvenile specimen, but still weighed in at between 0.8 – 0.95 tonnes. As adults, some hadrosaurs grew as big as T. Rex, again living in the late Cretaceous period.

The team used laser scanning (LiDAR) and computer modelling methods to create a range of 3D models of the specimens, attempting to reconstruct their body sizes and shape as in life. The laser scanner images the full mounted skeleton, resulting in a detailed 3D model in which each bone retains its spatial position and articulation. This provides a high resolution skeletal framework around which the body cavity and internal organs such as stomach, lungs and air sacs can be reconstructed. This has allowed calculation of body segment masses, centres of mass and moments of inertia for each animal – all the information that is needed to analyse body movements.

Having created their ‘best-guess’ reconstruction of each animal, they then varied the volumes of body segments and respiratory organs to find the maximum plausible range of mass for the animals. Even scientists cannot be sure exactly how fat or thin animals like T. rex were in life, and the team were interested in exactly how broad the range of possible values were for body mass. They believe that the lower weight estimates are most likely to be correct as there is no good reason for the dinosaurs to weigh more than they need to as this would affect their speed, energy use and demands on the respiratory system.

The team also measured the body mass of an ostrich, as an existing subject that would show how accurate their technique was, and found the results to be correct.

They will now use the results to further investigate the locomotion of dinosaurs, specifically how they ran.

Karl said: “Our technique allows people to see and decide for themselves how fat or thin the dinosaurs might have been in life. You can see the skeleton with a belly. Anyone from a five-year-old to a Professor can see it and say, ‘I think this reconstruction is too fat or too thin’.

He added: “This study will help us in our research on how dinosaurs ran in 3-D rather than 2-D as in previous studies.

“Reconstructing more dinosaurs in such detail will allow us to examine changes in body mass and particularly centre of mass as they evolved. As we know, dinosaurs evolved into birds. As they did so, the centre of mass moved forward and different walking styles evolved. Although the dinosaurs we have reconstructed are not very close relatives of the birds, we can nevertheless see a small forwards movement in the position of the centre of mass from Acrocanthosaurus atokensis to the T. rex, which lies closer to modern birds on the evolutionary lines.”

credited to sciencedaily.com

A missing link in the evolution of the front claw of living scorpions and horseshoe crabs was identified with the discovery of a 390 million-year-old fossil by researchers at Yale and the University of Bonn, Germany. The specimen, named Schinderhannes bartelsi, was found fossilized in slate from a quarry near Bundenbach in Germany, a site that yields spectacularly durable pyrite-preserved fossils — findings collectively known as the Hunsrück Slate. The Hunsrück Slate has previously produced some of the most valuable clues to understanding the evolution of arthropods – including early shrimp-like forms, a scorpion and sea spiders as well as the ancient arthropods trilobites.

"With a head like the giant Cambrian aquatic predator Anomalocaris and a body like a modern arthropod, the specimen is the only known example of this unusual creature," said Derek Briggs, director of Yale's Peabody Museum of Natural History and an author of the paper appearing in the journal Science.

Scientists have puzzled over the origins of the paired grasping appendages found on the heads of scorpions and horseshoe crabs. The researchers suggest that Schinderhannes gives a hint. Their appendages may be an equivalent to those found in the ancient predatory ancestor, Anomalocaris — even though creatures with those head structures were thought to have become extinct by the middle of the Cambrian Period, 100 million years before Schinderhannes lived.

The fossil's head section has large bulbous eyes, a circular mouth opening and a pair of segmented, opposable appendages with spines projecting inward along their length. The trunk section is made up of 12 segments, each with small appendages, and a long tail spine. Between the head and trunk, there is a pair of large triangular wing-like limbs — that likely propelled the creature like a swimming penguin, according to Briggs. Unlike its ancestors from the Cambrian period, which reached three feet in length, Schinderhannes is only about 4 inches long.

This finding caps almost 20 years of study by Briggs on the Hunsrück Slate. "Sadly, the quarry from which this fabulous material comes has closed for economic reasons, so the only additional specimens that are going to appear now are items that are already in collectors' hands and that may not have been fully prepared or realized for what they are," said Briggs.

credited to esciencenews.com

Some 60 million years ago, well after the demise of the dinosaurs, a giant relative of today’s boa constrictors, weighing more than a ton and measuring 42 feet long, hunted crocodiles in rain-washed tropical forests in northern South America, according to a new fossil discovery.

But the existence of such a large snake may also help clarify how hot the tropics became during an era when the planet, as a whole, was far warmer than it is now, and also how well moist tropical ecosystems can tolerate a much warmer global climate.

That last question is important in assessments of how human-driven global warming might affect the tropics. Some scientists foresee the Amazon’s drying up, for instance, although other work cuts against that conclusion.

The discovery and its climatic implications are described in Thursday’s edition of the journal Nature.

An independent critique of the work by Matthew Huber, an earth and climate scientist at Purdue, also published in Nature, said the findings provided a hint that the tropics could get a lot warmer than they are now, but also “attest to the resiliency of tropical ecosystems in the face of extreme warming.”

With scant precise evidence of past temperature changes on land in the tropics, there is still substantial debate about whether these regions have gotten much warmer than typical steamy tropical conditions today — with an annual average temperature of 75 to 79 degrees Fahrenheit.

The team examined how warm it had to be for a snake species to be that large by considering conditions favoring the largest living similar tropical snake, the green anaconda, said Jason J. Head, the lead author of the paper and a paleontologist at the University of Toronto. They concluded that Titanoboa could have thrived only if temperatures ranged from 86 to 93 degrees.

credited to nytimes.com

June 30, 1908, 7:14 a.m., central Siberia—Semen Semenov, a local farmer, saw “the sky split in two. Fire appeared high and wide over the forest.... From ... where the fire was, came strong heat.... Then the sky shut closed, and a strong thump sounded, and I was thrown a few yards.... After that such noise came, as if . . . cannons were firing, the earth shook ...”

Such is the harrowing testimony of one of the closest eyewitnesses to what scientists call the Tunguska event, the largest impact of a cosmic body to occur on the earth during modern human history. Semenov experienced a raging conflagration some 65 kilometers (40 miles) from ground zero, but the effects of the blast rippled out far into northern Europe and Central Asia as well. Some people saw massive, silvery clouds and brilliant, colored sunsets on the horizon, whereas others witnessed luminescent skies at night—Londoners, for instance, could plainly read newsprint at midnight without artificial lights. Geophysical observatories placed the source of the anomalous seismic and pressure waves they had recorded in a remote section of Siberia. The epicenter lay close to the river Podkamennaya Tunguska, an uninhabited area of swampy taiga forest that stays frozen for eight or nine months of the year.

Ever since the Tunguska event, scientists and lay enthusiasts alike have wondered what caused it. Although most observers generally accept that some kind of cosmic body, either an asteroid or a comet, exploded in the sky above Siberia, no one has yet found fragments of the object or any impact craters in the affected region. The mystery remains unsolved, but our research team, only the latest of a steady stream of investigators who have scoured the area, may be closing in on a discovery that will change our understanding of what happened that fateful morning.

The study of the Tunguska event is important because past collisions with extraterrestrial bodies have had major effects on the evolution of the earth. Some 4.4 billion years ago, for example, a Mars-size planetoid seems to have struck our young planet, throwing out enough debris to create our moon. And a large impact may have caused the extinction of the dinosaurs 65 million years ago. Even today cosmic impacts are evident. In July 1994 several astronomical observatories recorded the spectacular crash of a comet on Jupiter. And only last September, Peruvian villagers watched in awe and fright as a heavenly object streaked across the sky and landed not too far away with a loud boom, leaving a gaping pit 4.5 meters deep and 13 meters wide.

Using satellite observations of meteoric “flares” in the atmosphere (“shooting stars”) and acoustical data that record cosmic impacts on the surface of the earth, Peter Brown and his co-workers at the University of Western Ontario and Los Alamos National Laboratory estimated the rate of smaller impacts. The researchers have also extrapolated their findings to larger but rarer incidents such as the Tunguska event. The average frequency of Tunguska-like asteroidal collisions ranges from one in 200 years to one in 1,000 years. Thus, it is not unlikely that a similar strike could occur during our lifetimes. Luckily, the Tunguska impact took place in an unpopulated corner of the globe. Should something like it explode above New York City, the entire metropolitan area would be razed. Understanding the Tunguska event could help us prepare for such an eventuality and maybe even take steps to avoid its occurrence altogether.

The first step in preparing ourselves would be to decide whether the cosmic object that affected Siberia was an asteroid or a comet. Although the consequences are roughly comparable in either case, an important difference is that objects in the solar system that circle far away from the sun on long-period orbits before returning, such as comets, would hit the earth at much greater velocities than close-orbiting (short-period) bodies, such as asteroids. A comet that is significantly smaller than an asteroid thus could release the same kinetic energy in such a collision. And observers have much more difficulty detecting long-period objects before they enter the inner solar system. In addition, the probability that such objects will cross the earth’s orbit is low relative to the probability that asteroids will. For these reasons, confirmed comet impacts on the earth are so far unknown. Therefore, if the Tunguska event was in fact caused by a comet, it would be a unique occurrence rather than an important case study of a known class of phenomena. On the other hand, if an asteroid did explode in the Siberian skies that June morning, why has no one yet found fragments?

Part of the enduring mystery of the Tunguska event harks back to the stark physical isolation of central Siberia and the political turmoil that raged in Russia during the early 20th century, a time when the czarist empire fell and the Soviet Union emerged. These two factors delayed scientific field studies for nearly 20 years. Only in 1927 did an expedition led by Leonid Kulik, a meteorite specialist from the Russian Academy of Sciences, reach the Tunguska site. When Kulik got to the site, he was confronted with some almost unbelievable scenery. Amazingly, the blast had flattened millions of trees in a broad, butterfly-shaped swath covering more than 2,000 square kilometers (775 square miles). Furthermore, the tree trunks had fallen in a radial pattern extending out for kilometers from a central area where “telegraph poles,” a lone stand of partially burned tree stumps, still remained. Kulik interpreted this ravaged landscape as the aftermath of an impact of an iron meteorite. He then began to search for the resulting crater or meteorite fragments.

Kulik led three additional expeditions to the Tunguska region in the late 1920s and 1930s, and several others followed, but no one found clear-cut impact craters or pieces of whatever had hit the area. The dearth of evidence on-site gave rise to various explanatory hypotheses. In 1946, for instance, science-fiction writer Alexander Kazantsev explained the puzzling scene by positing a scenario in which an alien spacecraft had exploded in the atmosphere. Within a few years, the airburst theory gained scientific support and thereafter limited further speculation. Disintegration of a cosmic object in the atmosphere, between five and 10 kilometers above the surface, would explain most of the features investigators observed on the ground. Seismic observatory records, together with the dimensions of the devastation, allowed researchers to estimate the energy and altitude of the blast.

The lack of an impact crater also suggested that the object could not have been a sturdy iron meteorite but a more fragile object, such as a relatively rare, stony asteroid or a small comet. Russian scientists favored the latter hypothesis because a comet is composed of dust particles and ice, which would fail to produce an impact crater. Another explanation for the tumult in the Tunguska region claimed that the de­struc­tion resulted from the rapid combustion of methane gas released from the swampy ground into the air.

In 1975 Ari Ben-Menahem, a seismologist at the Weizmann Institute of Science in Rehovot, Israel, analyzed the seismic waves triggered by the Tunguska event and estimated that the energy released by the explosion was between 10 and 15 megatons in magnitude, the equivalent of 1,000 Hiroshima atomic bombs.

Astrophysicists have since created numerical simulations of the Tunguska event to try to decide among the competing hypotheses. The airburst of a stony asteroid is the leading interpretation. Models by Christopher F. Chyba, then at the NASA Ames Research Center, and his colleagues proposed in 1993 that the asteroid was a few tens of meters in diameter and that it exploded several kilometers above the ground. Comparison of the effects of nuclear test airbursts with the flattened pattern of the Tunguska forest seems to confirm this suggestion.

More recent simulations by N. A. Artemieva and V. V. Shuvalov, both at the Institute for Dynamics of Geospheres in Moscow, have envisioned an asteroid of similar size vaporizing five to 10 kilometers above Tunguska. In their model, the resulting fine debris and a downward-propagating gaseous jet then dispersed over wide areas in the atmosphere. These simulations do not, however, exclude the possibility that meter-size fragments may have survived the explosion and could have struck the ground not far from the blast.

Late last year Mark Boslough and his team at Sandia National Laboratories concluded that the Tunguska event may have been precipitated by a much smaller object than earlier estimates had suggested. Their supercomputer simulation showed that the mass of the falling cosmic body turned into an expanding jet of high-temperature gas traveling at supersonic speeds. The model also indicated that the impactor was first compressed by the increasing resistance of the earth’s atmosphere. As the descending body penetrated deeper, air resistance probably caused it to explode in an airburst with a strong flow of heated gas that was carried downward by its tremendous momentum. Because the fireball would have transported additional energy toward the surface, what scientists had thought to be an explosion between 10 and 20 megatons was more likely only three to five megatons, according to Boslough. All this simulation work only strengthened (and continues to strengthen) our desire to conduct fieldwork at the Tunguska site.

Our involvement with the Tunguska event began in 1991, when one of us (Longo) took part in the first Italian expedition to the site, during which he searched for microparticles from the explosion that might have become trapped in tree resin. Later, we stumbled on two obscure papers by Russian scientists, V. A. Koshelev and K. P. Florensky, that reported their discovery of a small body of water, Lake Cheko, roughly eight kilometers from the suspected epicenter of the phenomenon. In 1960 Koshelev speculated that Lake Cheko might be an impact crater, but Florensky rejected that idea. Florensky instead believed the lake was older than the Tunguska event, based on having found loose sediments as thick as seven meters below the bottom of the lake.

Word that a lake sat close to ground zero piqued our interest in mounting a field trip there because lake-bottom sediments can store a detailed record of events that occurred in the surrounding region, the basis of paleolimnological studies. Although our team knew little of Lake Cheko, we thought that we could perhaps apply paleolimnological techniques and find in the lake’s sediments clues to unravel the Tunguska mystery, as if the lake were the black box from a crashed airliner.

After circling the lake’s dark waters warily, the helicopter hovered precariously above the swampy lakeside (which was too soft for a landing) as we jumped down amid a torrential rainstorm. With eight blades rotating furiously above our heads, the resulting hurricane of air and water seemed set to sweep us away when at last we managed to unload our heavy cargo. With a roar, the craft lifted upward, and we were left drenched and exhausted near the edge of the lake, suddenly immersed in the deep silence of the Siberian wilderness. Any small relief we felt when the rain stopped was immediately forgotten as clouds of voracious mosquitoes descended on us like massed squadrons of tiny dive-bombers.

We spent the next two days organizing the camp, assembling our survey boat (a catamaran) and testing our equipment. Our studies would require a range of technologies, such as acoustic echo sounders, a magnetometer, subbottom acoustic profilers, a ground-penetrating radar, devices to recover sediment cores, an underwater television camera and a set of GPS receivers to enable study teams to track their position with a resolution of less than a meter.

For two weeks after that, our group surveyed the lake from the catamaran, tormented the entire time by hordes of mosquitoes and horseflies. These efforts focused on exploring the sedimentation and structure of the lake’s subbottom. Other team members, in the meantime, busied themselves with their own tasks. With his ground-penetrating radar, Michele Pipan, a geophysicist at the University of Trieste, gradually mapped the subsurface structures (some three to four meters deep) below the 500-meter shore perimeter. Eugene Kolesnikov, a geochemist at Moscow State, and his colleagues excavated trenches in peat deposits near the lake, a tough job given the resistance of the hard permafrost layer below the surface. Kolesnikov’s team searched the peat layers for chemical markers of the Tunguska event. At the same time, Romano Serra of Bologna University and Valery Nesvetailo of Tomsk State collected core samples from nearby tree trunks to study possible anomalies in the tree-ring patterns. Meanwhile, high above us, the aircraft that brought us to Krasnojarsk returned and circled the region to take aerial photographs so that we could compare them with those Kulik made some 60 years before.

We had assumed that the lake-bottom sediments might contain markers of the Tunguska event. After completing just a few runs across Lake Cheko with our high-resolution acoustic profiler, it became clear that the sediments blanketing the lake’s bottom were more than 10 meters thick. Some sediment particles had been transported to the lake by winds, but most of them came by way of the inflow of the little Kimchu River that fed Lake Cheko. We estimated that sediment deposition in a small body of water that stays frozen for most of the year would probably not exceed a few centimeters a year, so such a thick sediment layer might imply that the lake existed before 1908.

Soon our time in Tunguska was nearly over. The expedition members spent the last day frantically disassembling the boat, packing the equipment and dismantling the camp. When the helicopter arrived at noon the next day, we rushed to load all our stuff and ourselves into the hovering chopper amid the storm of human-made turbulence and finally began our return.

Back in our laboratories in Italy, the three of us completed processing our bathymetric data, which confirmed that the shape of Lake Cheko’s bottom differs significantly from those of other Siberian lakes, which typically feature flat bottoms. Most lakes in the region form when water fills the depressions left after the ubiquitous permafrost layer melts. The funnellike shape of Lake Cheko, in contrast, resembles those of known impact craters of similar size—for instance, the so-called Odessa crater, which was created 25,000 years ago by the impact of a small asteroid in what is now Odessa, Tex.

The idea that Lake Cheko might fill an impact crater became more attractive to us. But if the lake is indeed a crater excavated by a fragment of the Tunguska cosmic body, it cannot have been formed earlier than 1908. We sought evidence that the little lake existed before the event. Reliable, pre-1908 maps of this uninhabited region of Siberia are not easy to come by, but we found a czarist military map from 1883 that fails to show the lake. Testimony by local Evenk natives also asserts that a lake was produced by the 1908 explosion. But if the lake was not formed before 1908, how can one explain the thickness of the deposits carpeting its floor? Our seismic-reflection data revealed two distinct zones in the lake’s deposits: a thin, roughly meter-thick upper level of laminated, fine sediments typical of quiet deposition overlying a lower region of nonstratified, chaotic deposits.

Our survey team also observed the half-buried remains of tree trunks in the deeper part of the lake via underwater video. And high-frequency acoustic waves reflected back from the same zone showed a characteristic “hairy” pattern that could have resulted from the presence of the remains of trunks and branches. Perhaps these results are a trace of the forest obliterated by the impact.

To explain the lower chaotic deposits, we can imagine a cosmic body hitting soggy ground overlying a layer of permafrost several tens of meters thick. The impactor’s kinetic energy is transformed into heat, which melts the permafrost, releasing methane and water vapor and expanding the size of the resulting crater by as much as a quarter. At the same time, the impact would have plastered preexisting river and swamp deposits onto the flanks of the impact crater, where they would later be imaged as the chaotic deposits in our acoustic-echo profiles.

We are anxious to find out. Our team is now preparing to return later this year to attempt to drill the center of the lake to reach the dense seismic reflector. The year 2008 is the centennial of the Tunguska event. We hope it will also be the year the Tunguska mystery is solved.

Luca Gasperini, Enrico Bonatti and Giuseppe Longo have studied the Tunguska mystery for many years. Gasperini is a research scientist at the Institute of Marine Science in Bologna, Italy. Bonatti is professor of geodynamics at the University of Rome La Sapienza and special scientist at Columbia University's Lamont-Doherty Earth Observatory. Longo is professor of physics at the University of Bologna (www-th.bo.infn.it/tunguska).

credited to sciam.com

The platypus tops many people’s oddest mammal list, what with its ducklike bill and beaverlike tail. Its closest relatives, the echidnas, don’t get the press the platypus gets, but they are pretty weird, too, and are the only other monotremes, or egg-laying mammals, around.

Now Timothy Rowe of the University of Texas and colleagues report in The Proceedings of the National Academy of Sciences that the divergence may have occurred long before that. They used X-ray computer tomography to examine a 120-million-year-old fossil, Teinolophus trusleri. It is an ancestral platypus, they say, with some similar morphological features, in particular a canal in the jaw that the researchers say is evidence that Teinolophus had a duckbill.

The researchers conclude that the platypus and echidna branches of monotremes were already distinct at that early date. The findings also suggest that monotremes diversified at a slower rate than the other mammals.

credited to nytimes.com

A fossil of a primitive feathered dinosaur uncovered in China is helping scientists create a better model of how dinosaurs evolved into modern birds. The winged dinosaur is still in the process of being dated, and might have lived toward the end of the Jurassic period, which lasted from 208 to 144 million years ago.

The protobird is "very close to the point of divergence" at which a new branch of winged dinosaurs first took flight, said Xu.

The new species, called Anchiornis huxleyi, was discovered in the ashes of volcanoes that were active during the Jurassic and Cretaceous (144 to 65 million years ago) periods in what is now northeastern China.

Anchiornis, which is Greek for "close to bird," measured just 13 inches (34 centimeters) from head to tail and weighed about 4 ounces (110 grams).

The dinosaur's body and forelimbs were covered with feathers, and it "might have had some aerial capability," Xu said.

"Anchiornis is one of the smallest theropod dinosaurs ever uncovered," Xu explained. Theropods were a group of carnivorous dinosaurs that walked on two legs.

Taking Wing

The fossil provides new clues about how feathers, wings, and flight progressively appeared among theropods, along with evidence that certain types of feathered dinosaurs decreased in stature even as their forelimbs became elongated.

The compact structure of Anchiornis "reinforces the deduction that small size evolved early in the history of birds," Xu explained.

"The wrist is a big part of the formation of wings, and pivotal to flight," Xu added. "During flight, steering and flapping greatly depend on the wrist."

Despite this protobird's relatively advanced feathers and wrist, it is unclear if Anchiornis could actually engage in powered flight.

"Behavior and biomechanics are very difficult to determine solely from the fossil record, and perhaps flight is impossible to determine," said Mark Norell, chairman and curator of the division of paleontology at the American Museum of Natural History in New York.

"Feathers have lots of functions, and probably evolved as thermoregulators," said Norell, who closely examined the fossil during a trip to Beijing.

"Dinosaurs might have used feathers for sexual display or to make themselves appear bigger, or as camouflage to avoid predators," he said.

Patterns of spots and bars evident on one species of feathered dinosaur from China might have functioned as a camouflage defense, Norell added.

Prehistoric Paradise

Xu said that the region in northeastern China where most of the world's feathered dinosaurs, including Anchiornis, have been discovered is a virtual paradise for dinosaur hunting.

"This area has three circles of volcanic activity," with eruptions that intermittently covered and preserved entire biospheres starting from the early Jurassic.

"Volcanos periodically killed the animals and plants and preserved them perfectly in volcanic ash," he said.

"Sometimes the volcanic ash even preserves soft tissues, leaving behind an exceptional 3-D fossil."

credited to news.nationalgeographic.com

When Paul C. Sereno went hunting for dinosaur bones in the Sahara, his career took a sharp turn from paleontology to archaeology. The expedition found what has proved to be the largest known graveyard of Stone Age people who lived there when the desert was green.

In its first comprehensive report, published Thursday, the team described finding about 200 graves belonging to two successive populations. Some burials were accompanied by pottery and ivory ornaments. A girl was buried wearing a bracelet carved from a hippo tusk. A man was seated on the carapace of a turtle.

The most poignant scene was the triple burial of a petite woman lying on her side, facing two young children. The slender arms of the children reached out to the woman in an everlasting embrace. Pollen indicated that flowers had decorated the grave.

The sun-baked dunes at the site, known as Gobero, preserve the earliest and largest Stone Age cemetery in the Sahara, Dr. Sereno’s group reported in the online journal PLoS One. The findings, they wrote, open “a new window on the funerary practices, distinctive skeletal anatomy, health and diet of early hunter-fisher-gatherers, who expanded into the Sahara when climatic conditions were favorable.”

The research was also described at a news conference on Thursday in Washington at the National Geographic Society, a supporter of the project.

The initial inhabitants at Gobero, the Kiffian culture, were tall hunters of wild game who also fished with harpoons carved from animal bone. Later, a more lightly built people, the Ténérians, lived there, hunting, fishing and herding cattle.

Other scientists said the discovery appeared to provide spectacular evidence that nothing, not even the arid expanse of the Sahara, was changeless. About 100 million years ago, this land was forested and occupied by dinosaurs and enormous crocodiles. Around 50,000 years ago, people moved in and left stone tools and mounds of shells, fish bones and other refuse. The lakes dried up in the last Ice Age.

Then the rains and lakes of a fecund Sahara returned about 12,000 years ago, and remained, except for one 1,000-year interval, until about 4,500 years ago. Geologists have long known that the region’s basins retained mineral residue of former lakes, and other explorers have found scatterings of human artifacts from that time, as Dr. Sereno did at Gobero in 2000.

“Everywhere you turned, there were bones belonging to animals that don’t live in the desert,” he said. “I realized we were in the green Sahara.”

Human skeletons were eroding from the dunes, including jawbones with nearly full sets of teeth and finger bones of a tiny hand pointing up from the sand.

From an analysis of the skeletons and pottery, scientists identified the two successive cultures that occupied the settlement. The Kiffians, some of whom stood up to six feet tall, both men and women, lived there during the Sahara’s wettest period, between 10,000 and 8,000 years ago. They were primarily hunter-gatherers who speared huge lake perch with harpoons.

Elena A. A. Garcea, an archaeologist at the University of Cassino in Italy, identified ceramics with wavy lines and zigzag patterns as Kiffian, a culture associated with northern Africa. Pots bearing a pointillistic pattern were linked to the Ténérians, a people named for the Ténéré desert, a stretch of the Sahara known to Tuareg nomads as a “desert within a desert.”

Christopher M. Stojanowski, an archaeologist at Arizona State University, said the two cultures were “biologically distinct groups.” The bones and teeth showed that in contrast to the robust Kiffians, the Ténérians were typically short and lean and apparently led less rigorous lives.

The shapes of the Ténérian skulls are puzzling, researchers said, because they resemble those of Mediterranean people, not other nearby groups.

Asked if he had adjusted to the transition from dinosaur paleontology to Stone Age archaeology, Dr. Sereno said, “It’s still weird for me to be digging up my own species.”

credited to nytimes.com

A treasure trove of information about pre-human New Zealand has been found in feces from giant extinct birds, buried beneath the floor of caves and rock shelters for thousands of years.

Former PhD student Jamie Wood, from the University of Otago, discovered more than 1500 coprolites in remote areas across southern New Zealand, primarily from species of the extinct giant moa, which ranged up to 250 kilograms and three metres in height. Some of the feces recovered were up to 15 centimetres in length.

"Surprisingly for such large birds, over half the plants we detected in the feces were under 30 centimetres in height," says Dr Wood. "This suggests that some moa grazed on tiny herbs, in contrast to the current view of them as mainly shrub and tree browsers. We also found many plant species that are currently threatened or rare, suggesting that the extinction of the moa has impacted their ability to reproduce or disperse."

"New Zealand offers a unique chance to reconstruct how a `megafaunal ecosystem' functioned," says Professor Alan Cooper, Director of the Australian Centre for Ancient DNA, which performed the DNA typing.

"You can't do this elsewhere in the world because the giant species became extinct too long ago, so you don't get such a diverse record of species and habitats. Critically, the interactions between animals and plants we see in the poo provides key information about the origins and background to our current environment, and predicting how it will respond to future climate change and extinctions."

"When animals shelter in caves and rock shelters, they leave feces which can survive for thousands of years if dried out," Professor Cooper says. "Given the arid conditions, Australia should probably have similar deposits from the extinct giant marsupials. A key question for us is 'where has all the Australian poo gone?'"

Other University of Adelaide members of the research team include Dr Jeremy Austin, Dr Trevor Worthy and Mr Nicolas Rawlence from the Australian Centre for Ancient DNA, part of the University's newly-established Environment Institute.

The team's findings have recently been published in Quaternary Science Reviews, an international geological research journal.

credited to University of Adelaide (2009, January 13). Giant Bird Feces Record Pre-human New Zealand. ScienceDaily. Retrieved March 17, 2009, from http://www.sciencedaily.com­/releases/2009/01/090112110115.htm

Abundant tiny particles of diamond dust exist in sediments dating to 12,900 years ago at six North American sites, adding strong evidence for Earth's impact with a rare swarm of carbon-and-water-rich comets or carbonaceous chondrites, reports a nine-member scientific team.

Last year a 26-member team from 16 institutions proposed that a cosmic impact event, possibly by multiple airbursts of comets, set off a 1,300-year-long cold spell known as the Younger Dryas, fragmented the prehistoric Clovis culture and led to the extinction of a large range of animals, including mammoths, across North America. The team's paper was published in the Oct. 9, 2007, issue of the Proceedings of the National Academy of Sciences.

Now, reporting in the Jan. 2 issue of the journal Science, a team led by the University of Oregon's Douglas J. Kennett, a member of the original research team, report finding billions of nanometer-sized diamonds concentrated in sediments -- weighing from about 10 to 2,700 parts per billion -- in the six locations during digs funded by the National Science Foundation.

"The nanodiamonds that we found at all six locations exist only in sediments associated with the Younger Dryas Boundary layers, not above it or below it," said Kennett, a UO archaeologist. "These discoveries provide strong evidence for a cosmic impact event at approximately 12,900 years ago that would have had enormous environmental consequences for plants, animals and humans across North America."

The Clovis culture of hunters and gatherers was named after hunting tools referred to as Clovis points, first discovered in a mammoth's skeleton in 1926 near Clovis, N.M. Clovis sites later were identified across the United States, Mexico and Central America. Clovis people possibly entered North America across a land bridge from Siberia. The peak of the Clovis era is generally considered to have run from 13,200 to 12,900 years ago. One of the diamond-rich sediment layers reported sits directly on top of Clovis materials at the Murray Springs site.

The eight co-authors on the Science paper were: Kennett's father, James P. Kennett of the University of California, Santa Barbara; A. West of GeoScience Consulting in Dewey, Ariz.; C. Mercer of the National Institute for Materials Science in Tsukuba, Japan; Que Hee of the University of California, Los Angeles; L. Bement of the Oklahoma Archaeological Survey at the University of Oklahoma; T.E. Bunch and M. Sellers, both of Northern Arizona University; and W.S. Wolbach of DePaul University in Chicago.

credited to sciencedaily.com