Dinosaur Ideas Latest News for 2011
Giant 'Kraken' Lair Discovered: Cunning Sea Monster That Preyed On Ichthyosaurs - ScienceDaily (Oct. 10, 2011)
Across the Atlantic On Flotsam: New Fossil Findings Shed Light On the Origins of the Mysterious Bird Hoatzin - ScienceDaily (Oct. 4, 2011)
A New Species of Fossil Silky Lacewing Insects That Lived More Than 120 Million Years Ago - ScienceDaily (Oct. 5, 2011
Scientists Discover Rare Theropod Dinosaur Wounded in Action in Southern Utah - ScienceDaily (Sep. 19, 2011)
Primitive Birds Shared Dinosaurs' Fate - ScienceDaily (Sep. 19, 2011)
New Technique Fills Gaps in Fossil Record - ScienceDaily (Sep. 19, 2011)
Life After 'Snowball Earth': New Fossils Suggest Rapid Recovery of Life After Global Freeze - ScienceDaily (June 16, 2011)
Fossil of Giant Ancient Sea Predator Discovered - National Geographic Society
China Fossil Shows Bird, Crocodile Family Trees Split Earlier Than Thought - ScienceDaily (May 19, 2011)
Peculiar Feeding Mechanism of the First Vertebrates - ScienceDaily (May 20, 2011)
New Evidence Shows Mobile Animals Could Have Evolved Much Earlier Than Previously Thought - ScienceDaily (May 18, 2011)
Imaging Technology Reveals Intricate Details of 49-Million-Year-Old Spider - ScienceDaily (May 18, 2011)
Lizard Fossil Provides Missing Link to Show Body Shapes of Snakes and Limbless Lizards Evolved Independently - The findings appear in the journal Nature.
On Prehistoric Supercontinent of Pangaea, Latitude and Rain Dictated Where Species Lived - ScienceDaily (May 13, 2011)
Reptile 'Cousins' Shed New Light on End-Permian Extinction - ScienceDaily (May 5, 2011)
Battle Scars Found on an Ancient Sea Monster - ScienceDaily (May 4, 2011)
Immature Skull Led Young Tyrannosaurs to Rely on Speed, Agility to Catch Prey - ScienceDaily (May 10, 2011)
Jurassic Spider from China Is Largest Fossil Specimen Discovered - ScienceDaily (Apr. 22, 2011)
Fossil Sirenians, Related to Today's Manatees, Give Scientists New Look at Ancient Climate - ScienceDaily (Apr. 24, 2011)
Plankton Fossils Tell Tale of Evolution and Extinction - ScienceDaily (Apr. 26, 2011)
Did Dinosaurs Have Lice? Researchers Say It's Possible - ScienceDaily (Apr. 5, 2011)
'Thunder-Thighs' Dinosaur Discovered: Brontomerus May Have Used Powerful Thigh Muscles to Kick Predators - ScienceDaily (Feb. 23, 2011)
T. Rex More Hyena Than Lion: Tyrannosaurus Rex Was Opportunistic Feeder, Not Top Predator, Paleontologists Say - ScienceDaily (Feb. 22, 2011)
Fossil Antelopes Shed New Light on Today's Sub-Saharan Mammals - ScienceDaily (Feb. 17, 2011)
3-D Digital Dinosaur Track Download: A Roadmap for Saving at-Risk Natural History Resources - ScienceDaily (Feb. 12, 2011)
Newly Discovered Dinosaur Likely Father of Triceratops - ScienceDaily (Feb. 1, 2011)
No Leftovers for Tyrannosaurus Rex: New Evidence That T. Rex Was Hunter, Not Scavanger - Jan 29, 2011
Mass Extinction Linked to Ancient Climate Change, New Details Reveal - ScienceDaily (Jan. 27, 2011)
New Predator 'Dawn Runner' Discovered in Early Dinosaur Graveyard - ScienceDaily (Jan. 13, 2011)
Prehistoric Bird Used Club-Like Wings as Weapon - ScienceDaily (Jan. 5, 2011)
Giant 'Kraken' Lair Discovered: Cunning Sea Monster That Preyed On Ichthyosaurs
Long before whales, the oceans of Earth were roamed by a very different kind of air-breathing leviathan. Snaggle-toothed ichthyosaurs larger than school buses swam at the top of the Triassic Period ocean food chain, or so it seemed before Mount Holyoke College paleontologist Mark McMenamin took a look at some of their remains in Nevada. Now he thinks there was an even larger and more cunning sea monster that preyed on ichthyosaurs: a 'kraken' of such mythological proportions it would have sent Captain Nemo running for dry land.
McMenamin is presenting the results of his work on Oct. 10 at the annual meeting of the Geological Society of America in Minneapolis.
The evidence is at Berlin-Ichthyosaur State Park in Nevada, where McMenamin and his daughter spent a few days this summer. It's a site where the remains of nine 45-foot (14-meter) ichthyosaurs, of the species Shonisaurus popularis can be found. These were the Triassic's counterpart to today's predatory giant squid-eating sperm whales. But the fossils at the Nevada site have a long history of perplexing researchers, including the world's expert on the site: the late Charles Lewis Camp of U.C. Berkeley.
"Charles Camp puzzled over these fossils in the 1950s," said McMenamin. "In his papers he keeps referring to how peculiar this site is. We agree, it is peculiar."
Camp's interpretation was that the fossils probably represented death by an accidental stranding or from a toxic plankton bloom. But no one had ever been able to prove that the beasts died in shallow water. In fact more recent work on the rocks around the fossils suggest it was a deep water environment, which makes neatly arranged carcasses even more mysterious.
This question -- shallow or deep ocean death -- is what attracted McMenamin to the site.
"I was aware that anytime there is controversy about depth, there is probably something interesting going on," McMenamin said. And when they arrived at the remote state park and started looking at the fossils, McMenamin was struck by their strangeness.
"It became very clear that something very odd was going on there," said McMenamin. "It was a very odd configuration of bones."
First of all, the different degrees of etching on the bones suggested that the shonisaurs were not all killed and buried at the same time. It also looked like the bones had been purposefully rearranged. That it got him thinking about a particular modern predator that is known for just this sort of intelligent manipulation of bones.
"Modern octopus will do this," McMenamin said. What if there was an ancient, very large sort of octopus, like the kraken of mythology. "I think that these things were captured by the kraken and taken to the midden and the cephalopod would take them apart."
In the fossil bed, some of the shonisaur vertebral disks are arranged in curious linear patterns with almost geometric regularity, McMenamin explained.The proposed Triassic kraken, which could have been the most intelligent invertebrate ever, arranged the vertebral discs in double line patterns, with individual pieces nesting in a fitted fashion as if they were part of a puzzle.
Even more creepy: The arranged vertebrae resemble the pattern of sucker discs on a cephalopod tentacle, with each vertebra strongly resembling a coleoid sucker. In other words, the vertebral disc "pavement" seen at the state park may represent the earliest known self portrait.
But could an octopus really have taken out such huge swimming predatory reptiles? No one would have believed such a tale until the staff of the Seattle Aquarium set up a video camera at night a few years ago to find out what was killing the sharks in one of their large tanks. What they were shocked to discover was that a large octopus they had in the same tank was the culprit. The video of one of these attacks is available on the web to anyone who uses the search terms "shark vs octopus."
"We think that this cephalopod in the Triassic was doing the same thing," said McMenamin. Among the evidences of the kraken attacks are many more ribs broken in the shonisaur fossils than would seem accidental and the twisted necks of the ichthyosaurs. "It was either drowning them or breaking their necks."
Of course, it's the perfect Triassic crime because octopuses are mostly soft-bodied and don't fossilize well. Only their beaks, or mouth parts, are hard and the chances of those being preserved nearby are very low. That means the evidence for the murderous Kraken is circumstantial, which may leave some scientists rather skeptical. But McMenamin is not worried.
"We're ready for this," he said. "We have a very good case."
Taken from: ScienceDaily (Oct. 10, 2011)
Across the Atlantic On Flotsam: New Fossil Findings Shed Light On the Origins of the Mysterious Bird Hoatzin
A team comprising German, Brazilian and French scientists, including an ornithologist from the Senckenberg Research Institute Frankfurt, has examined fossil relatives of the South American Hoatzin(Opisthocomus hoazin), which point to African origins for the enigmatic bird.
The study was published by the journal Naturwissenschaften on October 5.
The Hoatzin is a funny old bird: a poor flyer, the chicks equipped with claws on their wings, it lives on the banks of the Amazon and Orinoco basins in South America. What is particularly unusual about this bird is its purely vegetarian diet. Digestion does not only take place in the stomach but above all in a greatly enlarged crop, where bacteria help to decompose the food. The digestive system of the Hoatzins is very reminiscent of that of a mammalian ruminat.
But not only is the anatomy of the bird unusual; its relationship is still unclear. Since its scientific description in 1776, the Hoatzin has been bracketed alternatively with game birds, cuckoos or the African turacos. However, no relationship with these groups has been proven convincingly until now. For this reason, the bird is usually allocated its own family and genus. The evolutionary origin of the Hoatzins has been unknown so far, and apart from some very fragmentary remains, there were no fossil remnants.
Now a team consisting of German, Brazilian and French researchers, including the ornithologist Gerald Mayr from the Senckenberg Research Institute, has not only described the earliest known fossil find of the mysterious bird group, but has also produce the first proof outside of South America.
Upper arm and shoulder girdle bones, around 23 million years old, from a site in southeast Brazil, which are kept in the Museu de História Natural de Taubaté in Brazil, are the first ever fossil finds of a Hoatzin. The large similarity between the fossils and the corresponding bones of the present-day Hoatzins suggest that the bird developed its unusual nutritional biology at a very early stage.
As well as the Brazilian findings the researchers also examined 17 million year old bones from Namibia, which revealed surprising findings on the earlier geographic distribution of the Hoatzins. Until now the African fossil finds, described a few years ago as Namibiavis senutae, were allocated to an extinct family of cranes. "However, this allocation can no longer be supported, because the finds demonstrate characteristic bone features of Hoatzins," explains Gerald Mayr.
When two related animal groups are discovered on different continents, this can be explained in principle by two mechanisms: either the continents were once connected by land, or the distribution took place directly across the water.
Africa and South America were once part of a supercontinent called Gondwana, but this had already broken up much longer than 20 million years ago, the continents being separated by the Atlantic. So Hoatzins must have crossed the ocean at some stage in order to get from one continent to the other.
But how does a bird, which is an especially poor long-distance flyer, manage to cross a sea that is over 1,000 kilometres wide? Even if the flying capabilities of the Hoatzin's ancestors were better, it is highly unlikely that they could have managed this distance in the air.
Gerald Mayr and his colleagues from Brazil and France have an explanation that is somewhat unexpected for birds: "We assume that the bird crossed the Atlantic upon drifting flotsam." This means of travel using flotsam is already familiar with regard to some primates, rodents and lizards, but it would be the first proof of a similar journey by a bird.
Due to the Cenozoic ocean currents and wind directions, a journey across the Atlantic was only probable in a westerly direction. The scientists assume, therefore, that "South America's most enigmatic bird" has its origins outside of South America and arrived there from Africa.
Taken from: ScienceDaily (Oct. 4, 2011)
A New Species of Fossil Silky Lacewing Insects That Lived More Than 120 Million Years Ago
A team of researchers from the Capital Normal University in Beijing (China) and the Institute of Biology and Soil Sciences in Vladivostok (Russia) has discovered a remarkable silky lacewing insect from the Mesozoic of China.
The study has been published recently in the open access journal ZooKeys.
The extant silky lacewings (the family Psychopsidae) may be recognized by their broad wing shape, dense venation, spectacularly patterned and hairy wings. Today, this family is very small, restricted only to southern Africa, southeastern Asia and Australia, but in the Mesozoic, it was much more widely distributed.
The new fossil silky lacewing -- Undulopsychopsis alexi -- was found from in the Yixian Formation of western Liaoning Province, one of the most productive Mesozoic fossil-bearing horizons in China. The species is characterized by the undulate wing margin, a unique condition amongst known Psychopsidae, and a number of unusual characters of the wing venation.
"The most important trait of this fossil is that it shares the features of two different families of neuropteran insects, the extant Psychopsidae (known also from the Mesozoic) and the extinct Mesozoic Osmylopsychopidae," said the author Vladimir Makarkin.
This discovery is expected to shed light on the evolutionary history of lacewings related to the family Psychopsidae.
Scientists Discover Rare Theropod Dinosaur Wounded in Action in Southern Utah
Raptor dinosaurs like the iconic Velociraptor from the movie franchise Jurassic Park are renowned for their "fear-factor." Their terrifying image has been popularized in part because members of this group possess a greatly enlarged talon on their foot -- analogous to a butcher's hook. Yet the function of the highly recurved claw on the foot of raptor dinosaurs has largely remained a mystery to paleontologists. This week a collaboration of scientists unveil a new species of raptor dinosaur discovered in southern Utah that sheds new light on this and several other long-standing questions in paleontology, including how dinosaurs evolved on the "lost continent" of Laramidia (western North America) during the Late Cretaceous -- a period known as the zenith of dinosaur diversity.
Their findings will be published in the journal PLoS ONE.
The new dinosaur -- dubbed Talos sampsoni -- is a member of a rare group of feathered, bird-like theropod dinosaurs whose evolution in North America has been a longstanding source of scientific debate, largely for lack of decent fossil material. Indeed, Talos represents the first definitive troodontid theropod to be named from the Late Cretaceous of North America in over 75 years. "Finding a decent specimen of this type of dinosaur in North America is like a lighting strike… it's a random event of thrilling proportions," said Lindsay Zanno, lead author of the study naming the new dinosaur. Zanno is an assistant professor of anatomy at the University of Wisconsin-Parkside and a research associate at the Field Museum of Natural History in Chicago, Illinois. Other members of the research team include Mike Knell (a graduate student at Montana State University) who discovered the new specimen in 2008 in the Kaiparowits Formation of Grand Staircase-Escalante National Monument (GSENM), southern Utah; Bureau of Land Management (BLM) paleontologist Alan Titus, leader of a decade-long paleontology reconnaissance effort in the monument; David Varricchio, Associate Professor of Paleontology, Montana State University; and Patrick O'Connor, Associate Professor of Anatomy, Ohio University Heritage College of Osteopathic Medicine.
Funding for the research was provided in part by the National Science Foundation, the Field Museum of Natural History, the Ohio University Heritage College of Osteopathic Medicine, and the Bureau of Land Management. Zanno's research was supported by a John Caldwell-Meeker Fellowship and by a Bucksbaum Fellowship for young scientists. The bones of Talos sampsoni will be on exhibit for the first time in the Past Worlds Observatory at the new Utah Museum of Natural History, Salt Lake City, Utah.
The Nature of the Beast Troodontid theropods are a group of feathered dinosaurs closely related to birds. Members of this group are among the smallest non-avian dinosaurs known (as small as 100 grams) and are considered among the most intelligent. The group is known almost exclusively from Asia and prior to the discovery of Talos sampsoni, only two species were recognized in the Late Cretaceous of North America -- one of which, the infamous Troodon, was one of the first dinosaurs ever named from North America. As a result of their distinctive teeth and the possible presence of seeds preserved as gut contents in one species, several scientists have proposed an omnivorous or herbivorous diet for at least some troodontids. Other species possess relatively blade-like teeth indicative of a carnivorous diet. Zanno's own work on theropod diet suggests that extensive plant eating was confined to more primitive members of the group, with more advanced members of the clade like Troodon and Talos likely consuming at least some prey.
Several troodontid specimens have recently been discovered that not only support a close relationship with birds but also preserve remarkable evidence of bird-like behavior. These include extraordinary specimens such as eggs and embryos within nests that document transitional phases in the evolution of bird-like reproductive physiology and egg-laying behavior, as well as specimens preserved in distinctive avian-like sleeping postures with their heads rotated back and tucked under their "wings." Other troodontids provide evidence of "four-winged" locomotor capabilities, and perhaps most extraordinary, plumage coloration.
With an estimated body mass of 38 kilograms, the newly discovered Talos sampsoni is neither the smallest nor largest troodontid known. Its skeleton indicates that the new species was much smaller and more slender than its famous cousin Troodon, which is known from sediments of the same age in the northern part of Laramidia (Alberta, Canada and Montana, USA). "Talos was fleet-footed and lightly built," Zanno says. "This little guy was a scrapper."
Interestingly, the holotype specimen of Talos also tells us something about theropod behavior, particularly raptor behavior. This is because the second toe -- that is, the one with the enlarged talon -- of the left foot of the new specimen is deformed, indicating that the animal suffered a fracture or bite during its life.
This Little Talos Takes a Beating
When the team first began studying the Talos specimen, they noticed some unusual features on the second digit of the left foot, but initially assumed they were related to the fact that it belonged to a new species. "When we realized we had evidence of an injury, the excitement was palpable," Zanno commented. "An injured specimen has a story to tell." That's because evidence of injury relates to function. The manner in which an animal is hurt can tell you something about what it was doing during life. An injury to the foot of a raptor dinosaur, for example, provides new evidence about the potential function of that toe and claw. In order to learn about the injury to the animal's foot, the team scanned the individual bones using a high-resolution Computed Tomography (CT) scanner, similar to those used by physicians to examine bones and other organs inside the human body.
"Although we could see damage on the exterior of the bone, our microCT approach was essential for characterizing the extent of the injury, and importantly, for allowing us to better constrain how long it had been between the time of injury and the time that this particular animal died," noted Patrick O'Connor, associate professor of anatomy at Ohio University. After additional CT scanning of other parts of the foot, Zanno and her team realized that the injury was restricted to the toe with the enlarged claw, and the rest of the foot was not impacted. More detailed study suggested that the injured toe was either bitten or fractured and then suffered from a localized infection.
"People have speculated that the talon on the foot of raptor dinosaurs was used to capture prey, fight with other members of the same species, or defend the animal against attack. Our interpretation supports the idea that these animals regularly put this toe in harm's way," says Zanno.
Perhaps even more interesting is the fact that the injured toe exhibits evidence of bone remodeling thought to have taken place over a period of many weeks to months, suggesting that Talos lived with a serious injury to the foot for quite a long time. "It is clear from the bone remodeling that this animal lived for quite some time after the initial injury and subsequent infection, and that whatever it typically did with the enlarged talon on the left foot, whether that be acquire prey or interact with other members of the species, it must have been capable of doing so fairly well with the one on the right foot," added O'Connor.
Trackways made by animals closely related to Talos suggest that they held the enlarged talon off the ground when walking. "Our data support the idea that the talon of raptor dinosaurs was not used for purposes as mundane as walking," Zanno commented. "It was an instrument meant for inflicting damage."
What's in a Name?
The name Talos pays homage to a mythological Greek figure of the same name, believed to have protected the island of Crete by throwing stones at invading ships. It is said that the Greek Talos, who was often depicted as a winged bronze figure, could run at lightening speed and circled the ancient island three times a day. The dinosaur Talos belongs to a group of theropods known to have feathery integument (and in some cases "wings"), lived on the small island continent of Laramidia or west North America during the Late Cretaceous, and was also a fast runner. The team chose the name Talos because of these similarities but also because the Greek Talos was said to have died from a wound to the ankle and it was clear that Talos had also suffered a serious wound to the foot. The species name "sampsoni" honors another famous figure -- Dr. Scott Sampson of the PBS series Dinosaur Train. Sampson, a research curator at the Utah Museum of Natural History and research faculty at the University of Utah, helped to spearhead a collaborative research effort known as the Kaiparowits Basin Project, a long-term research project that has been surveying and documenting the Late Cretaceous dinosaur fauna of the Kaiparowits Basin in southern Utah, with a focus on the Kaiparowits and Wahweap formations exposed in Grand Staircase-Escalante National Monument (GSENM). Thus far this effort has resulted in the discovery of up to a dozen new dinosaurs from GSENM that are challenging previous ideas regarding Late Cretaceous dinosaur evolution and diversity within Laramidia and spurring new ideas regarding dinosaur biogeography in the region.
A Tale of Two Continents
Dinosaurs of the Late Cretaceous were living in a greenhouse world. A warm and equitable global climate that was devoid of polar ice caps and above average spreading at mid-oceanic ridges caused massive flooding of low-lying continental areas and created expansive epicontinental seaways. In North America, a shallow seaway running from the Gulf of Mexico through to the Arctic Ocean divided the continent into two landmasses, East America (Appalachia) and West America (Laramidia) for several million years during the Late Cretaceous. It was during this time that the dinosaurs achieved their greatest diversity, and scientists have been working overtime to understand why. Take for example the dinosaurs of Laramidia. The natural assumption is that being large bodied, those dinosaurs that lived on the small island continent would have roamed the whole area. However, recent fossil discoveries, particularly new dinosaurs from the Kaiparowits Formation, tell us that the true pattern is exactly the opposite. Thus far the dinosaurs from the Kaiparowits Formation in southern Utah are entirely unique, even from those dinosaurs living just a few hundred miles to the north in what is now Montana and Alberta. Monument Paleontologist Alan Titus observed, "When we began looking in the remote Kaiparowits badlands we expected to see at least a few familiar faces. As it turns out, they are all new to science." And while recent discoveries from the Kaiparowits have substantiated this pattern for large-bodied herbivores like duck-bill and horned dinosaurs (for example Utahceratops), the pattern among small-bodied theropods was not clear. "We already knew that some of dinosaurs inhabiting southern Utah during the Late Cretaceous were unique," Zanno said, "but Talos tells us that the singularity of this ecosystem was not just restricted to one or two species. Rather, the whole area was like a lost world in and of itself."
A Monumental Discovery
Talos sampsoni is the newest member of a growing list of new dinosaur species that have been discovered in Grand Staircase Escalante National Monument (GSENM) in southern Utah. Former President Clinton founded the monument in 1996, in part to protect the world class paleontological resources entombed within its 1.9 million acres of unexplored territory. GSENM is one of the largest recently designated national monuments managed by the BLM, and one of the last pristine dinosaur graveyards in the US. The area has turned out to be a treasure trove of new dinosaur species, with at least 15 collected in just the past decade. Titus admits, "We had very few large fossils to substantiate the claim of 'World Class' paleontology when I started in 2000. Now, I feel GSENM could easily qualify as a world heritage site on the basis of its dinosaurs alone, dozens of which have been found preserving soft tissue." He also adds, "BLM support has been critical to the long term viability of the region's paleontology research and is paying off in countless ways both to the public and scientists."
Zanno, along with colleague Scott Sampson, named the first dinosaur from the monument -- Hagryphus giganteus -- in 2005. Hagryphus (widely touted in the press as the "turkey" dinosaur) is also a theropod dinosaur, but one that belongs to a different subgroup known as oviraptorosaurs (or egg thief reptiles). Other GSENM dinosaurs include five new horned dinosaurs including the recently described and bizarrely ornate Kosmoceratops and Utahceratops, three new duck-bill dinosaurs including the "toothy" Gryposaurus monumentensis, two new tyrannosaurs, as well as undescribed ankylosaurs (armored dinosaurs), marine reptiles, giant crocodyliforms, turtles, plants, and a host of other organisms.
The discovery of a new troodontid from the monument is the latest in a long string of incredible fossil discoveries from the area. "I was surprised when I learned that I had found a new dinosaur," Knell said. "It is a rare discovery and I feel very lucky to be part of the exciting research happening here in the monument." Knell stumbled across the remains of Talos sampsoni while scouring the badlands of the Kaiparowits Formation for fossil turtles as part of his dissertation research.
Work continues every year in GSENM and new, significant fossil finds are made every field season. Considering there are hundreds of thousands of acres of outcrop that have yet to be surveyed, it is no exaggeration to claim the region will remain an exciting research frontier for decades to come.
Taken from: ScienceDaily (Sep. 19, 2011)
Primitive Birds Shared Dinosaurs' Fate
A new study puts an end to the longstanding debate about how archaic birds went extinct, suggesting they were virtually wiped out by the same meteorite impact that put an end to dinosaurs 65 million years ago.
For decades, scientists have debated whether birds from the Cretaceous period -- which are very different from today's modern bird species -- died out slowly or were killed suddenly by the Chicxulub meteorite. The uncertainty was due in part to the fact that very few fossil birds from the end of this era have been discovered.
Now a team of paleontologists led by Yale researcher Nicholas Longrich has provided clear evidence that many primitive bird species survived right up until the time of the meteorite impact. They identified and dated a large collection of bird fossils representing a range of different species, many of which were alive within 300,000 years of the impact.
"This proves that these species went extinct very abruptly, in terms of geological time scales," said Longrich. The study appears the week of Sept. 19 in the journal Proceedings of the National Academy of Sciences.
The team examined a large collection of about two dozen bird fossils discovered in North America -- representing a wide range of the species that existed during the Cretaceous -- from the collections of Yale's Peabody Museum of Natural History, the American Museum of Natural History, the University of California Museum of Paleontology, and the Royal Saskatchewan Museum. Fossil birds from the Cretaceous are extremely rare, Longrich said, because bird bones are so light and fragile that they are easily damaged or swept away in streams.
"The birds that had been discovered hadn't really been studied in a rigorous way," Longrich said. "We took a much more detailed look at the relationships between these bones and these birds than anyone had done before."
Longrich believes a small fraction of the Cretaceous bird species survived the impact, giving rise to today's birds. The birds he examined showed much more diversity than had yet been seen in birds from the late Cretaceous, ranging in size from that of a starling up to a small goose. Some had long beaks full of teeth.
Yet modern birds are very different from those that existed during the late Cretaceous, Longrich said. For instance, today's birds have developed a much wider range of specialized features and behaviors, from penguins to hummingbirds to flamingoes, while the primitive birds would have occupied a narrower range of ecological niches.
"The basic bird design was in place, but all of the specialized features developed after the mass extinction, when birds sort of re-evolved with all the diversity they display today," Longrich said. "It's similar to what happened with mammals after the age of the dinosaurs."
Longrich adds that this study is not the first to suggest that archaic birds went extinct abruptly. "There's been growing evidence that these birds were wiped out at the same time as the dinosaurs," Longrich said. "But this new evidence effectively closes the book on the debate."
Other authors of the paper include Tim Tokaryk (Royal Saskatchewan Museum) and Daniel Field (Yale University).
Taken from ScienceDaily (Sep. 19, 2011)
New Technique Fills Gaps in Fossil Record
University of Pennsylvania evolutionary biologists have resolved a long-standing paleontological problem by reconciling the fossil record of species diversity with modern DNA samples.
Cataloging the diversity of life on Earth is challenging enough, but when scientists attempt to draw a phylogeny -- the branching family tree of a group of species over their evolutionary history -- the challenge goes from merely difficult to potentially impossible. The fossil record is the only direct evidence scientists have about the history of species diversity, but it can be full of holes or totally nonexistent, depending on the type of organisms. The only hope in such cases is to infer historical diversity from modern DNA sequences, but such techniques have a fatal flaw: the results they provide are demonstrably incorrect.
The Penn team has developed a new technique for analyzing phylogenies and shown that the results stand up against the known fossil history of whale species, a gold standard in terms of fossil records.
"We've put contemporary molecular approaches on equal footing with classical paleontological approaches," said Joshua B. Plotkin of the Department of Biology in Penn's School of Arts and Sciences and the Department of Computer and Information Science in the School of Engineering and Applied Science.
Plotkin conducted the research along with postdoctoral fellows Helene Morlon and Todd Parsons, both of Biology.
Their work will appear in the journal Proceedings of the National Academy of Sciences.
The limitations of the fossil record -- and the lack of good alternatives -- represent a longstanding problem in paleontology. Some species, due to the makeup of their bodies or the geology of the areas where they lived, don't leave fossils. If they leave any legacy to the present, it must be inferred from the DNA of their modern descendants, or from the descendents of their relatives.
For a few decades, scientists have compared the DNA of modern species, making mathematical inferences about the history of species diversity in a group going back to their most recent common ancestor. This reconstructive technique held much promise for the field, but a problem with the approach is now evident.
"When scientists use these phylogenetic techniques, they always infer patterns of increasing diversity. In whatever group of species they inspect, they see virtually no extinctions and a steadily increasing number of species over time," Plotkin said. "This molecular inference is problematic because it's known to be false. The fossil record clearly shows extinctions and long periods of diversity loss."
The cetaceans, a group of species that includes whales, dolphins and porpoises, are ideal for testing ideas about evolutionary diversification, as their fossil record is especially clear. Because they are large animals, and the sea floor is well suited to fossilization, paleontologists are confident that the cetaceans came into existence about 35 million years ago and reached a peak of diversity about 10 million years ago. The number of cetaceans then crashed from about 150 species to the 89 species in existence today.
"The problem with phylogenetic inferences is that you get the opposite view when you apply it to the cetaceans. You would see the number of whale species increasing over time, so that the 89 species we have today is the apex. But we know that this is flat-out wrong because it's directly contradicted by the boom-then-bust pattern in the fossil record."
This realization was a major blow for the field; if molecular reconstructions can't be trusted, there would be no way for scientists to ever learn the history of species that don't have good fossil records. The only hope was that phylogenetic methods could be refined.
In their study, Plotkin and his colleagues added new variables to these methods. The flaw in existing techniques was the reliance on a static rate of diversification. Because that variable could never be negative, the number of species inferred necessarily increased over time.
"What we've done is a fairly modest extension of these techniques, but we allow for changing rates of speciation and extinction over time and among lineages," Plotkin said. "Most importantly, we allow for periods of time during which the extinction rate exceeds the speciation rate."
When applied to the DNA of the 89 whale species that survive today, Plotkin's molecular method closely matched the dynamics in the number of whale species during the last 35 million years as determined through traditional paleontological approaches.
"It's almost miraculous that we can inspect the DNA sequences of organisms living today and figure out how many such species were present millions of years ago," Plotkin said. "We're studying some of the largest species to have ever existed, and we are deciphering their evolutionary history based on information encoded in microscopic DNA molecules."
The research was supported by the Centre National de la Recherche Scientifique, Burroughs Wellcome Fund, David and Lucile Packard Foundation, Alfred P. Sloan Foundation and James S. McDonnell Foundation
Taken from: ScienceDaily (Sep. 19, 2011)
Life After 'Snowball Earth': New Fossils Suggest Rapid Recovery of Life After Global Freeze
The first organisms to emerge after an ancient worldwide glaciation likely evolved hardy survival skills, arming themselves with tough exteriors to weather a frozen climate.
Researchers at MIT, Harvard University and Smith College have discovered hundreds of microscopic fossils in rocks dating back nearly 710 million years, around the time when the planet emerged from a global glaciation, or "Snowball Earth," event. The fossils are remnants of tiny, amoeba-like organisms that likely survived the harsh post-glacial environment by building armor and reaching out with microscopic "feet" to grab minerals from the environment, cobbling particles together to make protective shells.
The discovery is the earliest evidence of shell building, or agglutination, in the fossil record. The team found a diversity of fossils, suggesting life may have recovered relatively quickly following the first major Snowball Earth event. The researchers report their findings in an upcoming issue of Earth and Planetary Science Letters.
The widely held Snowball Earth theory maintains that massive ice sheets covered the planet from pole to pole hundreds of millions of years ago. Geologists have found evidence of two major snowball periods -- at 710 and 635 million years ago -- in glacial deposits that formed close to the modern equator. Fossil records illustrate an explosion of complex, multicellular life following the more recent ice age. However, not much is known about life between the two major glaciations -- a period of about 75 million years that, until now, exhibited few signs of life.
"We know quite well what happened before the first Snowball, but we have no idea what happened in between," says Tanja Bosak, assistant professor of geobiology at MIT, and the paper's lead author. "Now we're really starting to realize there's a lot of unexpected life here."
Ice Age armor
Bosak's colleagues, Francis Macdonald of Harvard and Sara Pruss of Smith, trekked to northern Namibia and Mongolia to sample cap-carbonate rocks -- the very first layers of sediment deposited after the first ice age. The team hauled the samples back to Cambridge, where Bosak dissolved the rocks in acid. She plated the residue on slides and looked for signs of fossilized life. "It's a little bit like looking at clouds, trying to pick out shapes and seeing if anything's consistent," Bosak says.
Peering at the sludge through a microscope, she discovered a sea of tiny dark ovals, each with a single notch at its edge. To get a closer look, Bosak used scanning electron microscopy to create high-resolution, three-dimensional images, revealing hollow, 10-micron-thick shells. Fossils from Namibia were mostly round; those from Mongolia, more tube-like. Most fossils contained a slit or neck at one end, from which the organism's pseudopodia, or feet, may have protruded.
Bosak analyzed the shells' composition using X-ray spectroscopy, finding a rough patchwork of silica, aluminum and potassium particles that the organism likely plucked from the environment and glued to its surface.
Bosak says these single-celled microbes may have evolved the ability to build shells to protect against an extreme deep-ocean environment, as well as a potentially growing population of single-celled species, some of which may have preyed on other organisms.
A Snowball window
"We can now say there really were these robust organisms immediately after the first glaciation," Bosak says. "Having opened this kind of window, we're finding all kinds of organisms related to modern organisms."
The closest modern relative may be testate amoebae, single-celled microbes found in forests, lakes and peat bogs. These tiny organisms have been known to collect particles of silica, clay minerals, fungi and pollen, cementing them into a hard cloak or shell. Bosak says testate amoebae were extremely abundant before the first Snowball Earth, although there is no robust evidence that the plentiful protist evolved its shell-building mechanism until after that ice age.
Bosak's guess is that the post-glacial environment was a "brine" teeming with organisms and newly evolved traits. She says the group plans to return to Mongolia to sample more rocks from the same time period, and hopes other researchers will start to investigate rates of evolutionary change in similar rocks.
Andrew Knoll, the Fisher Professor of Natural History and professor of earth and planetary sciences at Harvard, says the group's findings point to a potentially rich source of information about the kinds of life able to persist between glacial periods.
"To date, we've known very little about life between the two large ice ages," Knoll says. "With this in mind, the new discoveries are truly welcome."
Credit: ScienceDaily (June 16, 2011)
Fossil of Giant Ancient Sea Predator Discovered
Paleontologists have discovered that a group of remarkable ancient sea creatures existed for much longer and grew to much larger sizes than previously thought, thanks to extraordinarily well-preserved fossils discovered in Morocco.
The creatures, known as anomalocaridids, were already thought to be the largest animals of the Cambrian period, known for the "Cambrian Explosion" that saw the sudden appearance of all the major animal groups and the establishment of complex ecosystems about 540 to 500 million years ago. Fossils from this period suggested these marine predators grew to be about two feet long. Until now, scientists also thought these strange invertebrates -- which had long spiny head limbs presumably used to snag worms and other prey, and a circlet of plates around the mouth -- died out at the end of the Cambrian.
Now a team led by former Yale researcher Peter Van Roy (now at Ghent University in Belgium) and Derek Briggs, director of the Yale Peabody Museum of Natural History, has discovered a giant fossilized anomalocaridid that measures one meter (more than three feet) in length. The anomalocaridid fossils reveal a series of blade like filaments in each segment across the animal's back, which scientists think might have functioned as gills.
In addition, the creature dates back to the Ordovician period, a time of intense biodiversification that followed the Cambrian, meaning these animals existed for 30 million years longer than previously realized.
"The anomalocaridids are one of the most iconic groups of Cambrian animals," Briggs said. "These giant invertebrate predators and scavengers have come to symbolize the unfamiliar morphologies displayed by organisms that branched off early from lineages leading to modern marine animals, and then went extinct. Now we know that they died out much more recently than we thought."
The specimens are just part of a new trove of fossils from Morocco that includes thousands of examples of soft-bodied marine fauna dating back to the early Ordovician period, 488 to 472 million years ago. Because hard shells fossilize and are preserved more readily than soft tissue, scientists had an incomplete and biased view of the marine life that existed during the Ordovician period before the recent discoveries in Morocco. The animals found in Morocco inhabited a muddy sea floor in fairly deep water, and were trapped by sediment clouds that buried them and preserved their soft bodies.
"The new discoveries in Morocco indicate that animals characteristic of the Cambrian, such as the anomalocaridids, continued to have a considerable impact on the biodiversity and ecology of marine communities many millions of years later," Van Roy said.
The paper appears in the May 26 issue of the journal Nature. This research was supported by a National Geographic Society Research and Exploration grant and by Yale University.
China Fossil Shows Bird, Crocodile Family Trees Split Earlier Than Thought
A fossil unearthed in China in the 1970s of a creature that died about 247 million years ago, originally thought to be a distant relative of both birds and crocodiles, turns out to have come from the crocodile family tree after it had already split from the bird family tree, according to research led by a University of Washington paleontologist.
The only known specimen of Xilousuchus sapingensis has been reexamined and is now classified as an archosaur. Archosaurs, characterized by skulls with long, narrow snouts and teeth set in sockets, include dinosaurs as well as crocodiles and birds.
The new examination dates the X. sapingensis specimen to the early Triassic period, 247 million to 252 million years ago, said Sterling Nesbitt, a UW postdoctoral researcher in biology. That means the creature lived just a short geological time after the largest mass extinction in Earth's history, 252 million years ago at the end of the Permian period, when as much as 95 percent of marine life and 70 percent of land creatures perished. The evidence, he said, places X. sapingensis on the crocodile side of the archosaur family tree.
"We're marching closer and closer to the Permian-Triassic boundary with the origin of archosaurs," Nesbitt said. "And today the archosaurs are still the dominant land vertebrate, when you look at the diversity of birds."
The work could sharpen debate among paleontologists about whether archosaurs existed before the Permian period and survived the extinction event, or if only archosaur precursors were on the scene before the end of the Permian.
"Archosaurs might have survived the extinction or they might have been a product of the recovery from the extinction," Nesbitt said.
The research is published May 17 online in Earth and Environmental Science Transactions of the Royal Society of Edinburgh, a journal of Cambridge University in the United Kingdom.
Co-authors are Jun Liu of the American Museum of Natural History in New York and Chun Li of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, China. Nesbitt did most of his work on the project while a postdoctoral researcher at the University of Texas at Austin.
The X. sapingensis specimen -- a skull and 10 vertebrae -- was found in the Heshanggou Formation in northern China, an area with deposits that date from the early and mid-Triassic period, from 252 million to 230 million years ago, and further back, before the mass extinction.
The fossil was originally classified as an archosauriform, a "cousin" of archosaurs, rather than a true archosaur, but that was before the discovery of more complete early archosaur specimens from other parts of the Triassic period. The researchers examined bones from the specimen in detail, comparing them to those from the closest relatives of archosaurs, and discovered that X. sapingensis differed from virtually every archosauriform.
Among their findings was that bones at the tip of the jaw that bear the teeth likely were not downturned as much as originally thought when the specimen was first described in the 1980s. They also found that neural spines of the neck formed the forward part of a sail similar to that found on another ancient archosaur called Arizonasaurus, a very close relative of Xilousuchus found in Arizona.
The family trees of birds and crocodiles meet somewhere in the early Triassic and archosauriforms are the closest cousin to those archosaurs, Nesbitt said. But the new research places X. sapingensis firmly within the archosaur family tree, providing evidence that the early members of the crocodile and bird family trees evolved earlier than previously thought.
"This animal is closer to a crocodile, but it's not a crocodile. If you saw it today you wouldn't think it was a crocodile, especially not with a sail on its back," he said.
The research was funded by the National Science Foundation, the Society of Vertebrate Paleontology, the American Museum of Natural History and the Chinese Academy of Sciences.
Peculiar Feeding Mechanism of the First Vertebrates
A fang-like tooth on double upper lips, spiny teeth on the tongue and a pulley-like mechanism to move the tongue backwards and forwards -- this bizarre bite belongs to a conodont and, thanks to a fresh fossil find, has now been analyzed and reconstructed by a Swiss-French research team headed by paleontologists from the University of Zurich. Their analysis sheds some light on the evolutionary origin of jaws. Using a 3D animated model, the reconstruction shows for the first time how the first vertebrates fed.
Jaws made of bone are commonplace in the animal kingdom. However, how jaws developed in the course of evolution is still a mystery. Under the direction of paleontologist Nicolas Goudemand, a team of researchers from the University of Zurich and the European Synchrotron Radiation Facility set about solving this puzzle. Living and extinct jawless animals can yield clues as to the development of the jaw.
The researchers studied fossilized conodonts -- extinct, eel-shaped animals whose precise relationship with the actual vertebrates is still a matter of debate.
For their project, which was funded by the Swiss National Science Foundation and just published in the American journal PNAS, the researchers analyzed new conodont fossils that date from around the biggest mass extinction event at the boundary between the Permian and Triassic periods.
Multitasking thanks to teeth on upper lips and tongue
In some of these new fossils discovered in China, the researchers noticed several conjoined tooth-like structures that occupied an unusual position in the mouth. Based on this discovery and the re-evaluation of other unusually constructed conodont feeding apparatus, the scientists developed a 3D animated model that shows how conodonts fed: most conodonts had to have two upper lips, upon each of which there was a long, fang-like structure. The conodonts also had a kind of tongue bearing a complex set of spiny or comb-like 'teeth'. The 'tongue' rested on pulley-like cartilage and could be moved backwards and forwards thanks to two opposing muscles. The conodonts used the 'tongue' and lips to grab food before two pairs of relatively robust, sometimes molar-like 'throat teeth' ground and cut it up.
Similarity with lampreys
The conodonts' unique feeding mechanism is fairly similar to that of the extant lamprey, which is widely regarded as the extinct conodonts' nearest relative. The new findings confirm that conodonts are to be considered primitive vertebrates from an evolutionary point of view. Moreover, due to the comparative feeding mechanism and other similarities, lampreys and conodonts must have a common ancestor which was one of the first vertebrates. This common ancestor must also have had a tongue mounted on pulley-like cartilage and therefore eaten in the same manner as the conodonts.
New Evidence Shows Mobile Animals Could Have Evolved Much Earlier Than Previously Thought
A University of Alberta-led research team has discovered that billions of years before life evolved in the oceans, thin layers of microbial matter in shallow water produced enough oxygen to support tiny, mobile life forms.
The researchers say worm-like creatures could have lived on the oxygen produced by photosynthetic microbial material, even though oxygen concentrations in the surrounding water were not high enough to support life. The research was conducted in shallow lagoons in Venezuela where the high salt content is comparable to oceans older than 500 million years.
The link between biomats and animals is demonstrated by the trace-fossil record, which are tracks left behind by the movements of the worm-like creatures. The trace-fossil records for these animals date to at least 555 million years ago.
These findings suggest that the appearance of animals was not dependent on an oxygenated ocean. Rather, the earliest animals could have live within photosynthetic biomats and derived life-sustaining oxygen from that source.
Scientists believe that complex animals started on Earth roughly between 700 and 600 million years ago, when the oceans were just becoming fully oxygenated.
The researchers say their work opens the door to the search for life in early periods of Earth's history when it was believed there was absolutely no oxygen and no chance of finding life.
The research was led by U of A geologist Murray Gingras and geomicrobiologist Kurt Konhauser. The research was published May 15 online in Nature Geoscience.
Imaging Technology Reveals Intricate Details of 49-Million-Year-Old Spider
Scientists have used the latest computer-imaging technology to produce stunning three-dimensional pictures of a 49 million-year-old spider trapped inside an opaque piece of fossilized amber resin.
University of Manchester researchers, working with colleagues in Germany, created the intricate images using X-ray computed tomography to study the remarkable spider, which can barely be seen under the microscope in the old and darkened amber.
Writing in the international journal Naturwissenschaften, the scientists showed that the amber fossil -- housed in the Berlin Natural History Museum -- is a member of a living genus of the Huntsman spiders (Sparassidae), a group of often large, active, free-living spiders that are hardly ever trapped in amber.
As well as documenting the oldest ever huntsman spider, especially through a short film revealing astounding details, the scientists showed that even specimens in historical pieces of amber, which at first look very bad, can yield vital data when studied by computed tomography.
"More than 1,000 species of fossil spider have been described, many of them from amber," said Dr David Penney, from Manchester's Faculty of Life Sciences. "The best-known source is Baltic amber which is about 49 million years old, and which has been actively studied for over 150 years.
"Indeed, some of the first fossil spiders to be described back in 1854 were from the historically significant collection of Georg Karl Berendt, which is held in the Berlin Natural History museum. A problem here is that these old, historical amber pieces have reacted with oxygen over time and are now often dark or cracked, making it hard to see the animal specimens inside."
Berendt's amber specimens were supposed to include the oldest example of a so-called Huntsman spider but this seemed strange as huntsman spiders are strong, quick animals that would be unlikely to be trapped in tree resin. To test this, an international team of experts in the fields of fossils and living spiders, and in modern techniques of computer analysis decided to re-study Georg Berendt's original specimen and determine once and for all what it really was.
"The results were surprising," said Dr Penney. "Computed tomography produced 3D images and movies of astounding quality, which allowed us to compare the finest details of the amber fossil with similar-looking living spiders.
"We were able to show that the fossil is unquestionably a Huntsman spider and belongs to a genus called Eusparassus, which lives in the tropics and also arid regions of southern Europe today, but evidently lived in central Europe 50 million years ago.
"The research is particularly exciting because our results show that this method works and that other scientifically important specimens in historical pieces of darkened amber can be investigated and compared to their living relatives in the same way."
Professor Philip Withers, who established the Henry Moseley X-ray Imaging Facility -- a unique suite of 3D X-ray imagers covering scales from a metre to 50nm -- within Manchester's School of Materials, added: "Normally such fossils are really hard to detect because the contrast against the amber is low but with phase contrast imaging the spiders really jump out at you in 3D. Usually you have to go to a synchrotron X-ray facility to get good phase contrast, but we can get excellent phase contrast in the lab. This is really exciting because it opens up the embedded fossil archive not just in ambers."
Lizard Fossil Provides Missing Link to Show Body Shapes of Snakes and Limbless Lizards Evolved Independently
Until a recent discovery, theories about the origins and evolutionary relationships of snakes barely had a leg to stand on.
Genetic studies suggest that snakes are related to monitor lizards and iguanas, while their anatomy points to amphisbaenians ("worm lizards"), a group of burrowing lizards with snake-like bodies. The debate has been unresolved--until now. The recent discovery by researchers from the University of Toronto Mississauga and the Museum für Naturkunde Berlin, Germany of a tiny, 47 million-year-old fossil of a lizard called Cryptolacerta hassiaca provides the first anatomical evidence that the body shapes of snakes and limbless lizards evolved independently.
"This fossil refutes the theory that snakes and other burrowing reptiles share a common ancestry and reveals that their body shapes evolved independently," says lead author Professor Johannes Müller of Humboldt-Universität, Berlin.
The fossil reveals that amphisbaenians are not closely related to snakes, but instead are related to lacertids, a group of limbed lizards from Europe, Africa and Asia. "This is the sort of study that shows the unique contributions of fossils in understanding evolutionary relationships," says Professor Robert Reisz from the University of Toronto Mississauga, the senior author of the study. "It is particularly exciting to see that tiny fossil skeletons can answer some really important questions in vertebrate evolution."
The German research team, led by Müller and American graduate student Christy Hipsley, used X-ray computed tomography to reveal the detailed anatomy of the lizard's skull and combined the anatomy of Cryptolacerta and other lizards with DNA from living lizards and snakes to analyze relationships. Their results showed that Cryptolacerta shared a thickened, reinforced skull with worm lizards and that both were most closely related to lacertids, while snakes were related to monitor lizards like the living Komodo dragons.
Even though snakes and amphisbaeans separately evolved their elongate, limbless bodies, the discovery of Cryptolacerta reveals the early stages in the evolution of burrowing in lizards. By comparing Cryptolactera to living lizards with known lifestyles, co-author and U of T Mississauga paleontologist Jason Head determined that the animal likely inhabited leaf-litter environments and was an opportunistic burrower.
"Cryptolacerta shows us the early ecology of one of the most unique and specialized lizard groups, and also reveals the sequence of anatomical adaptations leading to amphisbaenians and their burrowing lifestyle," says Head. "Based on this discovery, it appears worm-lizards evolved head first."
The findings appear in the journal Nature.
On Prehistoric Supercontinent of Pangaea, Latitude and Rain Dictated Where Species Lived
More than 200 million years ago, mammals and reptiles lived in their own separate worlds on the supercontinent Pangaea, despite little geographical incentive to do so. Mammals lived in areas of twice-yearly seasonal rainfall; reptiles stayed in areas where rains came just once a year. Mammals lose more water when they excrete, and thus need water-rich environments to survive. Results are published in the Proceedings of the National Academy of Sciences.
Aggregating nearly the entire landmass of Earth, Pangaea was a continent the likes our planet has not seen for the last 200 million years. Its size meant there was a lot of space for animals to roam, for there were few geographical barriers, such as mountains or ice caps, to contain them.
Yet, strangely, animals confined themselves. Studying a transect of Pangaea stretching from about three degrees south to 26 degrees north (a long swath in the center of the continent covering tropical and semiarid temperate zones), a team of scientists led by Jessica Whiteside at Brown University has determined that reptiles, represented by a species called procolophonids, lived in one area, while mammals, represented by a precursor species called traversodont cynodonts, lived in another. Though similar in many ways, their paths evidently did not cross.
"We're answering a question that goes back to Darwin's time," said Whiteside, assistant professor of geological sciences at Brown, who studies ancient climates. "What controls where organisms live? The two main constraints are geography and climate."
Turning to climate, the frequency of rainfall along lines of latitude directly influenced where animals lived, the scientists write in a paper published this week in the online early edition of the Proceedings of the National Academy of Sciences. In the tropical zone where the mammal-relative traversodont cynodonts lived, monsoon-like rains fell twice a year. But farther north on Pangaea, in the temperate regions where the procolophonids predominated, major rains occurred only once a year. It was the difference in the precipitation, the researchers conclude, that sorted the mammals' range from that of the reptiles.
On Pangaea, the mammals needed a water-rich area, so the availability of water played a decisive role in determining where they lived. "It's interesting that something as basic as how the body deals with waste can restrict the movement of an entire group," Whiteside said.
In water-limited areas, "the reptiles had a competitive advantage over mammals," Whiteside said. She thinks the reptiles didn't migrate into the equatorial regions because they already had found their niche.
The researchers compiled a climate record for Pangaea during the late Triassic period, from 234 million years ago to 209 million years ago, using samples collected from lakes and ancient rift basins stretching from modern-day Georgia to Nova Scotia. Pangaea was a hothouse then: Temperatures were about 20 degrees Celsius hotter in the summer, and atmospheric carbon dioxide was five to 20 times greater than today. Yet there were regional differences, including rainfall amounts.
The researchers base the rainfall gap on variations in Earth's precession, or the wobble on its axis, coupled with the eccentricity cycle, based on Earth's orbital position to the sun. Together, these Milankovitch cycles influence how much sunlight, or energy, reaches different areas of the planet. During the late Triassic, the equatorial regions received more sunlight, thus more energy to generate more frequent rainfall. The higher latitudes, with less total sunlight, experienced less rain.
The research is important because climate change projections shows areas that would receive less precipitation, which could put mammals there under stress.
"There is evidence that climate change over the last 100 years has already changed the distribution of mammal species," said Danielle Grogan, a graduate student in Whiteside's research group. "Our study can help us predict negative climate effects on mammals in the future."
Contributing authors include Grogan, Paul Olsen from Columbia University, and Dennis Kent from Rutgers. The National Science Foundation and the Richard Salomon Foundation funded the research.
Reptile 'Cousins' Shed New Light on End-Permian Extinction
The end-Permian extinction, by far the most dramatic biological crisis to affect life on Earth, may not have been as catastrophic for some creatures as previously thought, according to a new study led by the University of Bristol.
An international team of researchers studied the parareptiles, a diverse group of bizarre-looking terrestrial vertebrates which varied in shape and size. Some were small, slender, agile and lizard-like creatures, while others attained the size of rhinos; many had knobbly ornaments, fringes, and bony spikes on their skulls.
The researchers found that, surprisingly, parareptiles were not hit much harder by the end-Permian extinction than at any other point in their 90 million-year history. Furthermore, the group as a whole declined and diversified time and time again throughout its history, and it was not until about 50 million years after the end-Permian crisis that the parareptiles finally disappeared.
During the end-Permian extinction, some 250 million years ago, entire groups of animals and plants either vanished altogether or decreased significantly in numbers, and the recovery of the survivors was at times slow and prolonged before new radiations took place.
By studying the fossil record, palaeontologists can examine how individual groups of organisms responded to the end-Permian event and assess just how dramatic it was. However, as the quality and completeness of the fossil record varies considerably, both geographically and stratigraphically, palaeontologists need to find a way to 'join the dots' and piece together the fragments of a complex mosaic to give a more satisfactory and better picture of ancient life's diversity.
The team led by Dr Marcello Ruta of Bristol's School of Earth Sciences, and including scientists from Germany, Brazil and North America, used the evolutionary relationships among known parareptiles to produce a corrected estimate of changing diversity through time.
Dr Marcello Ruta said: "Evolutionary relationships can be superimposed on a time scale, allowing you to infer missing portions of past diversity. They are powerful tools that complement and refine the known record of extinct diversity. If you visualize evolutionary relationships in the form of branching diagrams and then plot them on a time scale, new patterns begin to emerge, with gaps in the fossil record suddenly filling rapidly."
One of the team members, Juan Cisneros of the Universidade Federal do Piauí, Ininga, Brazil said: "It is as if ghosts from the past appear all of a sudden and join their relatives in a big family tree -- you have a bigger tree. This way, you can start analysing observed and extrapolated abundance of species through time, and you can quantify novel origination and extinction events that would otherwise go unnoticed if you were to look at known finds only."
Co-author Johannes Müller of the Museum für Naturkunde, Berlin added: "Researchers who investigate changing diversity through time have a huge battery of basic and advanced analytical and statistical methods at their disposal to study patterns of diversification and extinction. Classic text-book views of waxing and waning of groups through deep time will certainly benefit, where possible, from the use of evolutionary thinking."
University of Washington's Linda Tsuji, also part of the research team, concluded: "This is the first time that the history of parareptiles has been examined in such detail. But this is only the beginning. These bizarre-looking vertebrates continue to inspire generations of researchers, not only those interested in mass extinctions. They are abundant, diverse, and we still know very little about their biology. We hope that this study will initiate a more in-depth study of the response of terrestrial vertebrates to global catastrophes."
The new findings are published online in the journal Palaeontology
Battle Scars Found on an Ancient Sea Monster
Scars on the jaw of a 120-million-year-old marine reptile suggest that life might not have been easy in the ancient polar oceans. The healed bite wounds were probably made by a member of the same species. Such injuries give important clues about the social behaviour of extinct sea creatures from the time of dinosaurs.
Found in the remote desert near the town of Marree in northern South Australia, the fossilised skeleton belonged to an ichthyosaur, a dolphin-like marine reptile that lived during the 'Age of Dinosaurs'. Ichthyosaurs were fast swimming predators that fed on fish and squid-like animals. Adults would have been around six metres in length and had long-snouted heads with over 100 pointed, crocodile-like teeth.
When the ichthyosaur was alive, the Australian continent was still joined to Antarctica and would have been much further south than it is today close to the southern polar circle. What is now arid grassland was then the bottom of a vast inland sea that experienced freezing water temperatures and even seasonal icebergs.
The surprising discovery of well preserved bite marks on the bones of the ichthyosaur's lower jaw were made during painstaking cleaning and reassembly of its skeleton in the laboratory. Evidence of advanced healing indicates that the animal survived the attack and lived on for some time afterwards.
"Pathological traces on ancient fossilised bones and teeth give unique insights into the lives and social behaviours of extinct animals" says Benjamin Kear, one of the authors of the study and an Assistant Professor with the Palaeobiology Programme at Uppsala University. "Such finds have also rarely been reported in ichthyosaurs before."
The size and spacing of the tooth marks do match any potential predators or prey. Rather, they are most consistent with another adult ichthyosaur, suggesting that the wounds were inflicted during combat over food, mates or territory. Facial biting is a common social interaction observed in animals today and is often directed towards restraining the opponents jaws.
Immature Skull Led Young Tyrannosaurs to Rely on Speed, Agility to Catch Prey
While adult tyrannosaurs wielded power and size to kill large prey, youngsters used agility to hunt smaller game.
"It's one of the secrets of success for tyrannosaurs -- the different age groups weren't competing with each other for food because their diets shifted as they grew," said Ohio University paleontologist Lawrence Witmer.
Witmer is part of an international team of scientists from Japan, Mongolia and the United States that analyzed the youngest and most-complete known skull for any species of tyrannosaur, offering a new view of the growth and feeding strategies of these fearsome predators. The 70-million-year-old skull comes from a very young individual of the Mongolian dinosaur species known as Tarbosaurus bataar, the closest known relative of T. rex.
The analysis of the 11.4-inch skull, published in the Journal of Vertebrate Paleontology, revealed changes in skull structure that suggest that young tyrannosaurs had a different lifestyle than adults.
"We knew that adult Tarbosaurus were a lot like T. rex," said lead author Takanobu Tsuihiji, a former Ohio University postdoctoral fellow who is now a postdoctoral researcher at the National Museum of Nature and Science in Tokyo. "Adults show features throughout the skull associated with a powerful bite…large muscle attachments, bony buttresses, specialized teeth. The juvenile is so young that it doesn't really have any of these features yet, and so it must have been feeding quite differently from its parents."
The skull was found as part of an almost complete skeleton, missing only the neck and a portion of the tail. Based on careful analysis of the microstructure of the legs bones, co-author Andrew Lee of Ohio University (now at Midwestern University) estimated that the juvenile was only 2 to 3 years old when it died. It was about 9 feet in total length, about 3 feet high at the hip and weighed about 70 pounds. In comparison, Tarbosaurus adults were 35 to 40 feet long, 15 feet high, weighed about 6 tons and probably had a life expectancy of about 25 years, based on comparison with T. rex.
"This little guy may have been only 2 or 3, but it was no toddler…although it does give new meaning to the phrase 'terrible twos,'" said Witmer, Chang Professor of Paleontology at the Ohio University College of Osteopathic Medicine. "We don't know to what extent its parents were bringing it food, and so it was probably already a pretty capable hunter. Its skull wasn't as strong as the adult's, and would have had to have been a more careful hunter, using quickness and agility rather than raw power."
The different hunting strategies of juveniles and adults may have reduced competition among Tarbosaurus and strengthened their role as the dominant predators of their environment.
"The juvenile skull shows that there must have a change in dietary niches as the animals got older," Tsuihiji said. "The younger animals would have taken smaller prey that they could subdue without risking damage to their skulls, whereas the older animals and adults had progressively stronger skulls that would have allowed taking larger, more dangerous prey."
The late Cretaceous environment offered plenty of options for prey.
"Tarbosaurus is found in the same rocks as giant herbivorous dinosaurs like the long-necked sauropod Opisthocoelicaudia and the duckbill hadrosaur Saurolophus," said Mahito Watabe of the Hayashibara Museum of Natural Sciences in Okayama, who led the expedition to Mongolia in 2006 that uncovered the new skull. "But the young juvenile Tarbosaurus would have hunted smaller prey, perhaps something like the bony-headed dinosaur Prenocephale."
The juvenile skull also is important because it helps clarify the identity of small, potentially juvenile specimens of other tyrannosaur species previously found.
"The beauty of our new young skull is that we absolutely know for many good reasons that it's Tarbosaurus," Witmer said. "We can use this known growth series to get a better sense of whether some of these more controversial finds grew up to be Tarbosaurus, Tyrannosaurus or some other species."
Other authors on the article include Khishigjav Tsogtbaatar and Rinchen Barsbold of the Mongolian Paleontological Center; Takehisa Tsubamoto, Shigeru Suzuki and Yasuhiro Kawahara of the Hayashibara Biochemical Laboratories; and Ryan Ridgely of the WitmerLab at Ohio University. The research was funded by grants to Tsuihiji from the Japan Society of Promotion of Science and to Witmer and Ridgely from the U.S. National Science Foundation. The field work was supported by the Hayashibara Company Limited, Olympus, Mitsubishi Motor Company and Panasonic.
Jurassic Spider from China Is Largest Fossil Specimen Discovered
With a leg span of more than five inches, a recently named Jurassic period spider from China is the largest fossil specimen discovered, and one that has modern relatives in tropical climates today.
A research team of KU and Capital Normal University (Beijing) researchers said the spider belongs to the living genus Nephila, or golden orb-weavers. An extremely long range for any animal genus, the nephilids are example of living fossils. Nephilids are the largest web-weaving spiders alive today (body length up to 5 cm, leg span 15 cm) and are common to the tropical and subtropical regions today. This suggests that the paleoclimate of Daohugou, China, where the specimen was found, was probably similarly warm and humid during the Jurassic.
Nephila females weave some of the largest orb webs known (up to 1.5 m in diameter) with distinctive gold-colored silk to catch a wide variety of medium-sized to large insects, but occasionally bats and birds as by-catch. Typically, an orb-weaver spider first weaves a non-sticky spiral with space for sticky spirals in between. Unlike most other orb-weaving spiders, Nephila do not remove the non-sticky spirals after weaving the sticky spirals. This results in a 'manuscript paper' effect when the orb is seen in the sunlight, because the sticky spirals reflect the light while the non-sticky spirals do not, thus resembling musical staves.
This fossil finding provides evidence that golden orb-webs were being woven and capturing medium to large insects in Jurassic times, and predation by these spiders would have played an important role in the natural selection of contemporaneous insects.
The research was published in the online edition of Biology Letters. Paul A. Selden, Gulf-Hedberg Distinguished Professor at KU and director of the Paleontological Institute, as well as ChungKun Shih and Dong Ren, professors from Capital Normal University, Beijing, China, authored the research.
Fossil Sirenians, Related to Today's Manatees, Give Scientists New Look at Ancient Climate
What tales they tell of their former lives, these old bones of sirenians, relatives of today's dugongs and manatees. And now, geologists have found, they tell of the waters in which they swam.
While researching the evolutionary ecology of ancient sirenians -- commonly known as sea cows -- scientist Mark Clementz and colleagues unexpectedly stumbled across data that could change the view of climate during the Eocene Epoch, some 50 million years ago.
Clementz, from the University of Wyoming, published the results in a paper in this week's issue of the journal Science.
He and co-author Jacob Sewall of Kutztown University in Pennsylvania used their findings to dispute a popular scientific assumption about the temperature and composition of seawater during the time marked by the emergence of the first modern mammals.
The Sirenia, named for the sirens or mermaids of Greek myth, is an order of aquatic, plant-eating mammals that live in swamps, rivers, estuaries, marine wetlands and coastal waters.
Four species of "sea cows" are alive today, in two families and genera: the dugong, with one species, and manatees with three species.
Sirenia also includes the Steller's sea cow, extinct since the 18th century, and others known only from fossil remains. The order evolved during the Eocene more than 50 million years ago.
In their paper--"Latitudinal Gradients in Greenhouse Seawater δ18O: Evidence from Eocene Sirenian Tooth Enamel"--the scientists used the isotopic composition of sirenian fossils from a broad time period and geographic area, along with climate simulation data, to add to the long-running debate over Eocene climate.
"This study demonstrates the value of the fossil record, and of examining the deep time record of paleoclimatological events, so we can better understand climate change today," says Lisa Boush, program director in the National Science Foundation (NSF)'s Division of Earth Sciences, which funded the research.
"This novel approach will potentially transform our way of thinking about the hydrologic response to global climate change."
"I wasn't looking at it from this direction when we started the project," says Clementz, whose research is part of an NSF Career award.
"But once we started accumulating enough samples, we could step back and get a better understanding of the habitat and dietary preferences of these fossil species, and also of the big picture. We saw that it could be reflecting climate and environmental change."
A new look at climate during the Eocene, when Earth underwent a dramatic change, could help scientists better understand global climate change today.
Most scientists assumed that the oxygen isotopic composition of seawater in the past was very similar to that of today, with high values at low latitudes and low values at high latitudes.
Isotopes are variants of atoms of a particular chemical element, in this case oxygen, with differing numbers of neutrons.
"But when we looked at the oxygen isotopic values of the fossils from low-latitude sites for the Eocene, they were much lower than we would predict," says Clementz.
The finding suggests that low-latitude sites during the Eocene were much wetter than today.
"This created a very different distribution in the oxygen isotopic composition of seawater for this time interval, which would, in turn, significantly impact estimates of paleoclimate and paleotemperature in the distant past," says Clementz.
"Scientists have used this assumption of the oxygen isotopic values of seawater to constrain temperature estimates for the past."
In their paper, Clementz and Sewall show that the assumption may be flawed, which could mean that previous estimates of water temperature are incorrect.
Plankton Fossils Tell Tale of Evolution and Extinction
Scientists studying the fossils of tiny ocean-dwelling plankton, called foraminifera, have uncovered another piece in the puzzle of why species evolve or become extinct.
The issue of whether extinctions and evolution are controlled more by the environment or by the existing diversity of species in an ecosystem is one that scientists have been debating since Darwin's time.
Writing in the journal Science on April 15, researchers from Imperial College London and Cardiff University say their study of foraminifera, or 'forams', suggests that new species are more likely to evolve when there are fewer species already and that extinctions are more closely linked to a change in environment than they are to the number of existing species.
Forams are marine plankton measuring not more than half a millimetre across, smaller than a grain of sand. They are abundant in oceans the world over, where they have existed for over a hundred million years. When forams die, they sink into the seabeds where they accumulate in layers many kilometres deep, providing a largely unbroken record of their history.
They have distinct shells made from calcium carbonate, similar to the shells of snails and birds' eggs, which can tell scientists about the environment in which they lived. For these reasons forams make excellent subjects for studying changes in environment and evolution.
Advanced techniques in geochemistry and microscopy have allowed the scientists to interrogate the foram fossil record in greater resolution than ever before. This enabled the researchers to model the interactions between the diversity of different foram species, the climate and the species' ecology over time, in order to see what factors had the greatest impact on the species' evolution.
By looking at the shells under a microscope and using information derived from chemical analysis of the shells, the team was able to make interpretations about the environments the foraminifera were living in; for example, whether they lived in the surface waters and hosted even tinier photosynthetic organisms or whether they lived hundreds of meters down where the light and heat from the sun was greatly reduced.
Professor Andy Purvis, from the Department of Life Sciences at Imperial College London is a lead author of the study. He said: "Newly obtained paleontological data about forams and the environmental conditions they endured are only just starting to yield valuable information about how life has changed form and function over time. This work is another step towards improving our understanding the complexity of extinct ecosystems and could help scientists predict future changes in modern biodiversity."
Tracy Aze, co-author on the study and a PhD student in the School of Earth and Ocean Sciences at Cardiff University, said: "The fossil record is a critical resource for understanding how today's species might react to our changing climate because it is the only way to study evolution's winners and losers."
Co-author Dr Thomas Ezard, now at the Department of Mathematics at the University of Surrey, devised a mathematical framework to analyse the interactions of species diversity, climate and species behaviour whilst at Imperial College London. He said: "The richness of the foram fossil record lends itself ideally to detailed mathematical and statistical modelling. This richness provides us with the robust evidence we need to make predictions about how complex interactions drive evolutionary dynamics."
Dr Ezard concluded: "if we want to understand evolution fully, we need to acknowledge that not all species are one and the same. The astonishing abundance and diversity of these foraminifera provides crucial clues in awkward parts of evolution's puzzle."
Did Dinosaurs Have Lice? Researchers Say It's Possible
A new study louses up a popular theory of animal evolution and opens up the possibility that dinosaurs were early -- perhaps even the first -- animal hosts of lice.
The study, in Biology Letters, uses fossils and molecular data to track the evolution of lice and their hosts. It offers strong evidence, the researchers said, that the ancestors of lice that today feed on birds and mammals began to diversify before a mass extinction event killed off the dinosaurs about 65 million years ago.
"This study lends support to the idea that major groups of birds and mammals were around before the dinosaurs went extinct," said Kevin Johnson, an ornithologist with the State Natural History Survey at the University of Illinois and a principal investigator on the study. "If the lice were around, we know their hosts were probably around."
Scientists still are trying to understand the factors that led to the diversity of today's birds and mammals. One theory is that the extinction of the dinosaurs fostered the earliest stages of bird and mammal diversification and expansion (a process called "radiation") by opening vast new territories and types of habitats to them.
"Ducks do different things from owls, which do different things from parrots, for example," Johnson said, "and it was thought that after the dinosaurs went extinct that's when these birds or mammals diversified into these different niches."
"But based on the evidence from lice, the radiation of birds and mammals was already under way before the dinosaurs went extinct," he said.
Lice have developed unique methods for evading a host's defenses. Wing lice, for example, have elongated bodies that allow them to insert themselves between the barbs in a feather and thus evade preening. Gopher lice have grooves in the tops of their heads that clasp onto a single shaft of hair. This specialization makes it hard for lice to shift to other hosts. As a result, their evolutionary history coincides very closely with that of their hosts.
Johnson and his colleagues, including co-principal investigator Vincent Smith (a former postdoctoral researcher in Johnson's lab who now is at the Natural History Museum in London) built a partial family tree of lice by comparing the DNA sequences of genes from 69 present-day louse lineages. Changes in gene sequence are a reliable measure of relatedness among different species in the same group (organisms in the same order, family or genus, for example). And because these changes accumulate over time, they also can be used to create a rough timeline of the evolution of related groups of organisms.
"Lice are like living fossils," Smith said. "The record of our past is written in these parasites, and by reconstructing their evolutionary history we can use lice as markers to investigate the evolutionary history of their hosts."
The researchers used louse, bird and mammal fossils to anchor precise time points in the tree. These fossils are dated according to the age of the geologic formations in which they were found. This gives only a minimum age for the animal found embedded there, Johnson said.
"If the oldest dove fossil is 20 million years old, we know that doves must have been around at that time," Johnson said, "so we know that the split that occurred between doves and the closest relative of doves must have occurred before 20 million years ago."
The oldest fossils found so far that resemble modern bird and mammal groups are less than 65 million years old, Johnson said. This led to the hypothesis that major bird and mammal lineages appeared only after the dinosaurs went extinct.
But more recent studies of the genetic changes in major groups of birds and mammals suggest that many of them were around before the dinosaurs disappeared.
The new study supports this idea, Johnson said.
"Our analysis suggests that both bird and mammal lice began to diversify before the mass extinction of dinosaurs," Johnson said. "And given how widespread lice are on birds, in particular, and also to some extent on mammals, they probably existed on a wide variety of hosts in the past, possibly including dinosaurs."
Many scientists believe that birds are the descendants of feathered dinosaurs, Jonson said. "So maybe birds just inherited their lice from dinosaurs."
Taken from: ScienceDaily (Apr. 5, 2011)
'Thunder-Thighs' Dinosaur Discovered: Brontomerus May Have Used Powerful Thigh Muscles to Kick Predators
ScienceDaily (Feb. 23, 2011) - A new dinosaur named Brontomerus mcintoshi, or “thunder-thighs” after its enormously powerful thigh muscles, has been discovered in Utah, USA. The new species is described in a paper recently published in the journal Acta Palaeontologica Polonica by an international team of scientists from the UK and the US.
A member of the long-necked sauropod group of dinosaurs which includes Diplodocus and Brachiosaurus, Brontomerus may have used its powerful thighs as a weapon to kick predators, or to help travel over rough, hilly terrain. Brontomerus lived about 110 million years ago, during the Early Cretaceous Period, and probably had to contend with fierce “raptors” such as Deinonychus and Utahraptor.
The fossilised bones of two specimens of Brontomerus mcintoshi — an adult and a juvenile — were rescued from a previously looted and damaged quarry in eastern Utah by researchers from the Sam Noble Museum. Paleontologists speculate that the larger specimen is the mother of the younger and would have weighed around 6 tons, about the size of a large elephant, and measured 14 meters in length. At a third of the size, the smaller specimen would have weighed about 200 kg, the size of a pony, and been 4.5 m long.
The authors classified the new genus based on an incomplete skeleton including bones from the shoulder, hip, ribs, vertebrae and some unidentifiable fragments. They used the bones to identify Brontomerus’ unique features, primarily the shape of the ilium (hip bone), which, in the case of Brontomerus, is unusually large in comparison to that of similar dinosaurs. The wide, blade-shaped bone projects forward ahead of the hip socket, providing a proportionally massive area for the attachment of muscles.
The shape of the bone indicates that the animal would likely have had the largest leg muscles of any dinosaur in the sauropod family. This is reflected in the name Brontomerus, which literally means “thunder-thighs.” The dinosaur’s species name, mcintoshi, was chosen in honor of John “Jack” McIntosh, a retired physicist at Wesleyan University, Conn., and lifelong avocational paleontologist.
“Brontomerus mcintoshi is a charismatic dinosaur and an exciting discovery for us,” said first author Mike Taylor, a researcher in the Department of Earth Sciences at University College London. “When we recognised the weird shape of the hip, we wondered what its significance might be, but we concluded that kicking was the most likely. The kick would probably have been used when two males fought over a female, but given that the mechanics were all in place it would be bizarre if it wasn’t also used in predator defense.”
Other marks on the bones give additional clues to Brontomerus’ lifestyle and environment. Co author Matt Wedel, assistant professor of anatomy at Western University of Health Sciences, Pomona, Calif., explained: “The shoulder blade of Brontomerus has unusual bumps that probably mark the boundaries of muscle attachments, suggesting that Brontomerus had powerful forelimb muscles as well. It’s possible that Brontomerus mcintoshi was more athletic than most other sauropods. It is well established that far from being swamp-bound hippo-like animals, sauropods preferred drier, upland areas; so perhaps Brontomerus lived in rough, hilly terrain and the powerful leg muscles were a sort of dinosaur four-wheel drive.”
While Brontomerus’ unusual hip structure and enormous thigh muscles place it on the list of most extreme dinosaurs, it is also a significant find for another reason. It is one more in a number of finds over the past 20 years that challenge the previously held idea that sauropods began to disappear in the Early Cretaceous period.
“Because sauropods were the most abundant dinosaurs found during the Jurassic period and the rarest during the Early Cretaceous, there’s long been the perception that sauropods were successful in the Jurassic and were replaced by duckbills and horned dinosaurs in the Cretaceous,” explained Wedel. “In the past 20 years, however, we are finding more sauropods from the Early Cretaceous period, and the picture is changing. It now seems that sauropods may have been every bit as diverse as they were during the Jurassic, but much less abundant and so much less likely to be found.”
T. Rex More Hyena Than Lion: Tyrannosaurus Rex Was Opportunistic Feeder, Not Top Predator, Paleontologists Say
ScienceDaily (Feb. 22, 2011) - The ferocious Tyrannosaurus rex has been depicted as the top dog of the Cretaceous, ruthlessly stalking herds of duck-billed dinosaurs and claiming the role of apex predator, much as the lion reigns supreme in the African veld.
But a new census of all dinosaur skeletons unearthed over a large area of eastern Montana shows that Tyrannosaurus was too numerous to have subsisted solely on the dinosaurs it tracked and killed with its scythe-like teeth.
Instead, argue paleontologists John "Jack" Horner from the Museum of the Rockies and Mark B. Goodwin from the University of California, Berkeley, T. rex was probably an opportunistic predator, like the hyena in Africa today, subsisting on both carrion and fresh-killed prey and exploiting a variety of animals, not just large grazers.
"In our census, T. rex came out very high, equivalent in numbers to Edmontosaurus, which many people had thought was its primary prey," said Horner, curator of paleontology at the Museum of the Rockies in Bozeman, Mont., and Regents Professor at Montana State University. "This says that T. rex is not a cheetah, it's not a lion. It's more like a hyena."
"This putative apex predator is as abundant in the upper layers of the Hell Creek Formation as the herbivores, its reputed primary food source," added Goodwin, a curator in UC Berkeley's Museum of Paleontology and assistant director of the museum. "And it's even more plentiful in the other two-thirds of the formation. This supports the view that T. rex benefited from a much wider variety of food sources than live prey."
The dinosaur census in the Hell Creek Formation of Montana, which dates from 65-95 million years ago, was begun in 1999 by Horner and Goodwin with the financial and occasional field support of Nathan Myhrvold, former chief technology officer for Microsoft Corp. and co-founder of Intellectual Ventures of Bellevue, Wash. The results, authored by Horner, Goodwin and Myhrvold, were published Feb. 9 in the open-access journal PLoS ONE.
Normally, Goodwin said, top predators are one-third or one-fourth as abundant as their prey, because of the larger energy needs of carnivores. Opportunistic hunters like the hyena, however, can be twice as abundant as the top predators.
"If you count the lions and the leopards and the cheetahs in the Serengeti, the number still does not equal the number of hyenas, because hyenas have a much wider food source," Horner said. "Cheetahs, for example, only go after things that are really fast. They don't eat turtles. But a hyena will eat a turtle, or anything else that it can catch or is dead."
Similarly, T. rex was eating anything it could, he said. "There's no evidence that T. rex could run very fast, so it wasn't out there being a cheetah. If it could get a sick animal, it would."
Horner suggests that juvenile and young adult T. rex may have been primarily flesh eaters, while the older adults, which developed proportionally larger, bone-crushing teeth as they aged, also consumed the bones and marrow of their prey.
Horner and Goodwin, together and separately, have been digging for dinosaurs in Eastern Montana for decades. The fossils date from a time when the area bordered an inland sea, which periodically advanced and withdrew over coastal plains, depositing sediment that was later exposed and heavily eroded. When Horner started his census of dinosaurs in the Hell Creek Formation around Fort Peck Lake in 1999, he teamed up with Goodwin to re-examine some of the dinosaurs discovered in the area.
Since then, through lab analysis and annual summer digs, they have shown that one named species, Torosaurus, was just a big, aged Triceratops; two dome-headed dinosaurs, Dracorex and Stygimoloch, were merely younger members of the genus Pachycephalosaurus; and the so-called Nanotyrannus was just a juvenile T. rex.
Once these fossils had been properly identified, Homer and Goodwin were able to catalog the species and relative ages of known dinosaurs in the formation, which is about 100 meters thick at exposed areas covering some 1,000 square kilometers. The census included only skeletal remains, not teeth, because the paleontologists wanted a record of the maturity of each specimen, and teeth tell little about the age of a dinosaur at death, Goodwin said.
Collating only skeletons containing three or more bones, the researchers counted 23 Triceratops, five Tyrannosaurus and five Edmontosaurus within the Upper Hell Creek Formation. The youngest or "upper" formation dates from between 65 and 70 million years ago, just before the purported mass extinction of the dinosaurs that was attributed to a comet or asteroid impact.
A census of older sediments -- the lower Hell Creek formation -- turned up 11 Triceratops, 11 T. rex and six Edmontosaurus partial skeletons, along with fossil bones of three other dinosaurs: Thescelosaurus and Ornithomimus, two bird-like, bipedal meat-eaters reaching some 12 feet in length at maturity; and Ankylosaurus, an armored, four-legged plant-eater with a club tail.
"Small juveniles and older adults were relatively rare compared to large juveniles and subadults for all the dinosaurs," Goodwin said. This could be explained if juveniles lived in other locations, which is not uncommon in some species. The largest adults may simply have been relatively rare.
"This adds to an emerging picture of what the dinosaur fauna looked like during the late Cretaceous," he said.
Horner noted the greater variety of dinosaurs in the older sediments, the Lower Hell Creek Formation, compared to the younger "Upper" formation.
"Definitely there was a change in population leading up to the Cretaceous-Tertiary boundary, so something was happening to the faunas prior to the impact," he said. "During the 10 million years after dinosaur diversity peaked 75 million years ago, the dinosaurs dwindled pretty fast, and there weren't many left at the end."
The work was supported by individual donations from James Kinsey, Catherine B. Reynolds and Homer Hickam, as well as Intellectual Ventures, the Windway Foundation, the Smithsonian Institution and the University of California Museum of Paleontology.
Fossil Antelopes Shed New Light on Today's Sub-Saharan Mammals
ScienceDaily (Feb. 17, 2011) — New fossil discoveries have provided a glimpse into the biogeographic configuration of Africa over the last seven million years.
Modern-day Africa south of the Sahara is home to a unique variety of mammals, a great number of which are not found anywhere else in the world. Biogeographers have long recognized that sub-Saharan Africa constitutes one of the world's six major mammalian biogeographic divisions, termed 'realms'. However, the historical development of these continental regions of biogeographic diversity has been little explored.
Description of 6-million-year-old fossil antelopes from the Middle Awash in Ethiopia's Afar Region has now provided new information on the development of today's sub-Saharan mammalian community. The new fossils are identified as a spiral-horned antelope named Prostrepsiceros cf. vinayaki. These Ethiopian fossils are closely related to species previously described from the Indian Subcontinent and Arabia and constitute the first African record of this otherwise Eurasian antelope. The discovery of a Eurasian antelope in Africa nearly six million years ago (Mya) is of significance given the extraordinary isolation of sub-Saharan antelope communities today. The new fossils therefore signal a period of time when mammalian dispersal between Africa and Eurasia remained less restricted than today.
More information on the historical development of modern African biogeography is gleaned from a review of the African record of fossil bovids (the natural group comprising antelopes, oxen, and kin). By seven Mya and up to five Mya, the composition of African bovids is already clearly distinguished from that of Europe and Asia; however, barriers to mammalian dispersal among these three continental regions are much weaker than in the modern world. This is evidenced by the retained presence of very similar species, such as the Middle Awash fossil antelope and multiple species of tragoportacin antelopes, a now extinct group that at this time ranged widely across Eurasia and Africa.
In contrast, the record of fossil bovids after five Mya indicates extremely limited faunal exchange taking place between Africa and Eurasia. Despite the presence of very large fossil assemblages from the last five million years, there are few records of closely related bovid species shared between African and Eurasian sites throughout this time. The study proposes that a major biogeographic break occurred around five million years ago, after which time the proportion of Eurasian taxa in Africa decreased significantly, beginning to resemble the situation in sub-Saharan Africa today. African fossil sites from between six and five million years ago, such as those from the Middle Awash from which the hominid Ardipithecus kadabba has been named, are then recognized to lie just before this notable increase in African biogeographic isolation.
The Ethiopian biogeographic realm therefore appears to have had a distinct history of ever-increasing isolation over the last seven million years. The modern African sub-Saharan mammalian community may be understood to be the vestiges of a once wider-ranging and more broadly connected African mammalian fauna. The causes of the gradual geographic restriction of Africa's mammals over time are not clear, but global climate change may be implicated. With gradual cooling and drying taking place globally since 17 Mya, strengthened latitudinal climatic gradients might have created ecological barriers to dispersal between the African continent to the south and the Eurasian landmass to the north. With the onset of the northern hemisphere glaciation and ice age cycles of the last 2.5 million years, intensified subtropical aridity and the expansion of the Saharan and Arabian deserts probably played a major role in the modern-day isolation of sub-Saharan mammalian communities.
The last seven million years is the time during which hominids, the human line from our last common ancestor with chimpanzees, evolved and dispersed from Africa. The earliest hominids are known from about seven to five Mya and include Ardipithecus kadabba from the Middle Awash, Orrorin tugenensis from Kenya, and Sahelanthropus tchadensis from Chad. Bovids have a very large and rich fossil record and are usually among the most abundant fossil taxa found at hominid sites. Studies on the bovid record therefore provide one of the best proxies for reconstructing large-scale paleobiological patterns as well as direct evidence for the contexts of early human evolution. Through description of the new Middle Awash specimens and a review of the bovid fossil record, this paper also sheds light on the continental-scale biogeographical context of early human evolution.
3-D Digital Dinosaur Track Download: A Roadmap for Saving at-Risk Natural History Resources
ScienceDaily (Feb. 12, 2011) — Portable laser scanning technology allows researchers to tote their latest fossil discovery from the field to the lab in the form of lightweight digital data stored on a laptop. But sharing that data as a 3D model with others requires standard formats that are currently lacking, say paleontologists at Southern Methodist University.
Portable 3D laser technology preserves Texas dinosaur's rare footprint. (Credit: Image courtesy of Southern Methodist University)
The SMU researchers used portable laser scanning technology to capture field data of a huge 110 million-year-old Texas dinosaur track and then create to scale an exact 3D facsimile. They share their protocol and findings with the public -- as well as their downloadable 145-megabyte model -- in the online scientific journal Palaeontologia Electronica.
The model duplicates an actual dinosaur footprint fossil that is slowly being destroyed by weathering because it's on permanent outdoor display, says SMU paleontologist Thomas L. Adams, lead author of the scientific article. The researchers describe in the paper how they created the digital model and discuss the implications for digital archiving and preservation. Click here for the download link.
"This paper demonstrates the feasibility of using portable 3D laser scanners to capture field data and create high-resolution, interactive 3D models of at-risk natural history resources," write the authors.
"3D digitizing technology provides a high-fidelity, low-cost means of producing facsimiles that can be used in a variety of ways," they say, adding that the data can be stored in online museums for distribution to researchers, educators and the public.
SMU paleontologist Louis L. Jacobs is one of the coauthors on the article.
"The protocol for distance scanning presented in this paper is a roadmap for establishing a virtual museum of fossil specimens from inaccessible corners across the globe," Jacobs said.
Paleontologists propose the term "digitype" for digital models
Scientists increasingly are using computed tomography and 3D laser scanners to produce high-quality 3D digital models, say Adams and his colleagues, including to capture high-resolution images from remote field sites.
SMU's full-resolution, three-dimensional digital model of the 24-by-16-inch Texas footprint is one of the first to archive an at-risk fossil, they say.
The SMU paleontologists propose the term "digitype" for such facsimiles, writing in their article "High Resolution Three-Dimensional Laser-scanning of the type specimen of Eubrontes (?) Glenrosensis Shuler, 1935, from the Comanchean (Lower Cretaeous) of Texas: Implications for digital archiving and preservation."
Laser scanning is superior to other methods commonly used to create a model because the procedure is noninvasive and doesn't harm the original fossil, the authors say. Traditional molding and casting procedures, such as rubber or silicon molds, can damage specimens.
But the paleontologists call for development of standard formats to help ensure data accessibility.
"Currently there is no single 3D format that is universally portable and accepted by all software manufacturers and researchers," the authors write.
Digitype is baseline for measuring future deterioration
SMU's digital model archives a fossil that is significant within the scientific world as a type specimen -- one in which the original fossil description is used to identify future specimens. The fossil also has cultural importance in Texas. The track is a favorite from well-known fossil-rich Dinosaur Valley State Park, where the iconic footprint draws tourists.
The footprint was left by a large three-toed, bipedal, meat-eating dinosaur, most likely the theropod Acrocanthosaurus. The dinosaur probably left the footprint as it walked the shoreline of an ancient shallow sea that once immersed Texas, Adams said. The track was described and named in 1935 as Eubrontes (?) glenrosensis. Tracks are named separately from the dinosaur thought to have made them, he explained.
"Since we can't say with absolute certainty they were made by a specific dinosaur, footprints are considered unique fossils and given their own scientific name," Adams said.
The fossilized footprint, preserved in limestone, was dug up in the 1930s from the bed of the Paluxy River in north central Texas about an hour's drive southwest of Dallas. In 1933 it was put on prominent permanent display in Glen Rose, Texas, embedded in the stone base of a community bandstand on the courthouse square.
The footprint already shows visible damage from erosion, and eventually it will be destroyed by gravity and exposure to the elements, Adams said. The 3D model provides a baseline from which to measure future deterioration, he said.
In comparing the 3D model to an original 1930s photograph made of the footprint, the researchers discovered that some surface areas have fractured and fallen away. By comparing the 3D model with a synthetically altered version, the researchers were able to calculate volume change, which in turn enables reconstruction of lost volume for restoration purposes.
Model comprises 52 scans totaling 2 gigabytes
Adams and his research colleagues took a portable scanner to the bandstand site to capture the 3D images. They employed a NextEngine HD Desktop 3D scanner and ScanStudio HD PRO software running on a standard Windows XP 32 laptop. The scanner and laptop were powered from outlets on the bandstand. The researchers used a tent to control lighting and maximize laser contrast.
Because of the footprint's size -- about 2 feet by 1.4 feet (64 centimeters by 43 centimeters) -- multiple overlapping images were required to capture the full footprint.
Raw scans were imported into Rapidform XOR2 Redesign to align and merge them into a single 3D model. The final 3D model was derived from 52 overlapping scans totaling 2 gigabytes, the authors said.
The full-resolution 3D digital model comprises more than 1 million poly-faces and more than 500,000 vertices with a resolution of 1.2 millimeters. It is stored in Wavefront format. In that format the model is about 145 megabytes. The model is free for downloading from a link on Palaeontologia Electronica's web site.
3D digital footprint also available as a QuickTime virtual object
A smaller facsimile is also available from the journal as a QuickTime Virtual Reality object. In that format, users can slide their mouse pointer over the 3D footprint image to drag it to a desired viewing angle, and zoom and pan. Click here for the link to the QuickTime video.
Adams, a doctoral candidate in the Roy M. Huffington Department of Earth Sciences at SMU, describes the SMU researchers' protocol in a video at www.smuresearch.com, which also carries a link to the journal article and an image slideshow.
Besides the 3D model, included with the Palaeontologia Electronica article is a link to a pdf of the original 1935 scientific article in which SMU geology professor Ellis W. Shuler described and identified the dinosaur that made the track.
Shuler's article, no longer in print, is "Dinosaur Track Mounted in the Band Stand at Glen Rose, Texas," published in Field & Laboratory. The clay molds and plaster casts Shuler made of the bandstand track are now lost, Adams said. Click here for the article.
Besides Adams and Jacobs, other co-authors on the article are paleontologists Christopher Strganac and Michael J. Polcyn in the Roy M. Huffington Department of Earth Sciences at SMU.
The research was funded by the Institute for the Study of Earth and Man at SMU
Newly Discovered Dinosaur Likely Father of Triceratops
ScienceDaily (Feb. 1, 2011) — Triceratops and Torosaurus have long been considered the kings of the horned dinosaurs. But a new discovery traces the giants' family tree further back in time, when a newly discovered species appears to have reigned long before its more well-known descendants, making it the earliest known member of its family.
| The skull on the left is the Titanoceratops skull, the missing parts of which were reconstructed to look like a Pentaceratops. The illustration on the right shows the missing parts of the frill (shaded). (Credit: Image courtesy of Yale University) |
The new species, called Titanoceratops after the Greek myth of the Titans, rivaled Triceratops in size, with an estimated weight of nearly 15,000 pounds and a massive eight-foot-long skull.
Titanoceratops, which lived in the American southwest during the late Cretaceous period around 74 million years ago, is the earliest known triceratopsin, suggesting the group evolved its large size more than five million years earlier than previously thought, according to Nicholas Longrich, the paleontologist at Yale who made the discovery. The finding, which will appear in an upcoming issue of the journal Cretaceous Research, helps shed light on the poorly understood origins of these giant horned dinosaurs.
Longrich was searching through scientific papers when he came across a description of a partial skeleton of a dinosaur discovered in New Mexico in 1941. The skeleton went untouched until 1995, when it was finally prepared and identified incorrectly as Pentaceratops, a species common to the area. When the missing part of its frill -- the signature feature of the horned dinosaurs -- was reconstructed for display in the Oklahoma Museum of Natural History, it was modeled after Pentaceratops.
"When I looked at the skeleton more closely, I realized it was just too different from the other known Pentaceratops to be a member of the species," Longrich said, adding that the specimen's size indicated that it likely weighed about twice as much as adult Pentaceratops. The new species is very similar to Triceratops, but with a thinner frill, longer nose and slightly bigger horns, Longrich said.
Instead, Longrich believes that Titanoceratops is the ancestor of both Triceratops and Torosaurus, and that the latter two split several millions years after Titanoceratops evolved. "This skeleton is exactly what you would expect their ancestor to look like," he said.
Titanoceratops was probably only around for about a million years, according to Longrich, while the triceratopsian family existed for a total of about 10 million years and roamed beyond the American southwest into other parts of the country and as far north as Canada.
In order to confirm the discovery beyond any trace of a doubt, Longrich hopes paleontologists will find other fossil skeletons that include intact frills, which would help confirm the differences between Titanoceratops and Pentaceratops.
"There have got to be more of them out there," Longrich said.
No Leftovers for Tyrannosaurus Rex: New Evidence That T. Rex Was Hunter, Not Scavanger
The findings end a long-running debate about the hunting behaviour of this awesome predator.
Scientists from the Zoological Society of London (ZSL) used an ecological model based on predator relationships in the Serengeti to determine whether scavenging would have been an effective feeding strategy for T. rex.
Previous attempts to answer the question about T. rex's hunting behaviour have focused on its morphology. The flaw in this approach is that two species can possess similar physical features and still have very different hunting strategies, such as vultures and eagles.
Lead author Dr Chris Carbone, says "By understanding the ecological forces at work, we have been able to show that scavenging was not a viable option for T. rex as it was out-competed by smaller, more abundant predatory dinosaurs.
"These smaller species would have discovered carcasses more quickly, making the most of 'first-come-first-served' opportunities."
Like polar bears and lions, the authors conclude that an individual T. rex would have roamed over large distances to catch its prey, potentially areas several times the size of Greater London.
This research now opens the door to look at the behaviour of T. rex as a hunter.
Mass Extinction Linked to Ancient Climate Change, New Details Reveal
ScienceDaily (Jan. 27, 2011) - About 450 million years ago, Earth suffered the second-largest mass extinction in its history -- the Late Ordovician mass extinction, during which more than 75 percent of marine species died. Exactly what caused this tremendous loss in biodiversity remains a mystery, but now a team led by researchers at the California Institute of Technology (Caltech) has discovered new details supporting the idea that the mass extinction was linked to a cooling climate.
"While it's been known for a long time that the mass extinction is intimately tied to climate change, the precise mechanism is unclear," says Seth Finnegan, a postdoctoral researcher at Caltech and the first author of the paper published online in Science on January 27. The mass extinction coincided with a glacial period, during which global temperatures cooled and the planet saw a marked increase in glaciers. At this time, North America was on the equator, while most of the other continents formed a supercontinent known as Gondwana that stretched from the equator to the South Pole.
By using a new method to measure ancient temperatures, the researchers have uncovered clues about the timing and magnitude of the glaciation and how it affected ocean temperatures near the equator. "Our observations imply a climate system distinct from anything we know about over the last 100 million years," says Woodward Fischer, assistant professor of geobiology at Caltech and a coauthor.
The fact that the extinction struck during a glacial period, when huge ice sheets covered much of what's now Africa and South America, makes it especially difficult to evaluate the role of climate. "One of the biggest sources of uncertainty in studying the paleoclimate record is that it's very hard to differentiate between changes in temperature and changes in the size of continental ice sheets," Finnegan says. Both factors could have played a role in causing the mass extinction: with more water frozen in ice sheets, the world's sea levels would have been lower, reducing the availability of shallow water as a marine habitat. But differentiating between the two effects is a challenge because until now, the best method for measuring ancient temperatures has also been affected by the size of ice sheets.
The conventional method for determining ancient temperature requires measuring the ratios of oxygen isotopes in minerals precipitated from seawater. The ratios depend on both temperature and the concentration of isotopes in the ocean, so the ratios reveal the temperature only if the isotopic concentration of seawater is known. But ice sheets preferentially lock up one isotope, which reduces its concentration in the ocean. Since no one knows how big the ice sheets were, and these ancient oceans are no longer available for scientists to analyze, it's hard to determine this isotopic concentration. As a result of this "ice-volume effect," there hasn't been a reliable way to know exactly how warm or cold it was during these glacial periods.
But by using a new type of paleothermometer developed in the laboratory of John Eiler, Sharp Professor of Geology and professor of geochemistry at Caltech, the researchers have determined the average temperatures during the Late Ordovician -- marking the first time scientists have been able to overcome the ice-volume effect for a glacial episode that happened hundreds of millions of years ago. To make their measurements, the researchers analyzed the chemistry of fossilized marine animal shells collected from Quebec, Canada, and from the midwestern United States.
The Eiler lab's method, which does not rely on the isotopic concentration of the oceans, measures temperature by looking at the "clumpiness" of heavy isotopes found in fossils. Higher temperatures cause the isotopes to bond in a more random fashion, while low temperatures lead to more clumping.
"By providing independent information on ocean temperature, this new method allows us to know the isotopic composition of 450-million-year-old seawater," Finnegan says. "Using that information, we can estimate the size of continental ice sheets through this glaciation." And with a clearer idea of how much ice there was, the researchers can learn more about what Ordovician climate was like -- and how it might have stressed marine ecosystems and led to the extinction.
"We have found that elevated rates of climate change coincided with the mass extinction," says Aradhna Tripati, a coauthor from UCLA and visiting researcher in geochemistry at Caltech.
The team discovered that even though tropical ocean temperatures were higher than they are now, moderately sized glaciers still existed near the poles before and after the mass extinction. But during the extinction intervals, glaciation peaked. Tropical surface waters cooled by five degrees, and the ice sheets on Gondwana grew to be as large as 150 million cubic kilometers -- bigger than the glaciers that covered Antarctica and most of the Northern Hemisphere during the modern era's last ice age 20,000 years ago.
"Our study strengthens the case for a direct link between climate change and extinction," Finnegan says. "Although polar glaciers existed for several million years, they only caused cooling of the tropical oceans during the short interval that coincides with the main pulse of mass extinction."
In addition to Finnegan, Eiler, Tripati, and Fischer, the other authors on the Science paper, "The magnitude and duration of Late Ordovician-Early Silurian glaciation magnitude," are Kristin Bergmann, a graduate student at Caltech; David Jones of Amherst College; David Fike of Washington University in St. Louis; Ian Eisenman, a postdoctoral scholar at Caltech and the University of Washington; and Nigel Hughes of the University of California, Riverside.
This research was funded by the Agouron Institute and the National Science Foundation.
New Predator 'Dawn Runner' Discovered in Early Dinosaur Graveyard
ScienceDaily (Jan. 13, 2011) — A team of paleontologists and geologists from Argentina and the United States on Jan. 13 announced the discovery of a lanky dinosaur that roamed South America in search of prey as the age of dinosaurs began, approximately 230 million years ago.
Sporting a long neck and tail and weighing only 10 to 15 pounds, the new dinosaur has been named Eodromaeus, the "dawn runner."
"It really is the earliest look we have at the long line of meat eaters that would ultimately culminate in Tyrannosaurus Rex near the end of the dinosaur era," said Paul Sereno, University of Chicago paleontologist and National Geographic Explorer-in-Residence. "Who could foretell what evolution had in store for the descendants of this pint-sized, fleet-footed predator?"
Sereno and his colleagues describe a near-complete skeleton of the new species, based on the rare discovery of two individuals found side-by-side, in the Jan. 14, 2011 issue of the journal Science. The paper presents a new snapshot of the dawn of the dinosaur era -- a key period that has garnered less attention than the dinosaurs' demise. "It's more complex than some had supposed," Sereno said.
Set in picturesque foothills of the Andes, the site of discovery is known as the "Valley of the Moon," said the report's lead author, Ricardo Martinez of Argentina's National University of San Juan. For dinosaur paleontologists, it is like no other.
"Two generations of field work have generated the single best view we have of the birth of the dinosaurs," Martinez said. "With a hike across the valley, you literally walk over the graveyard of the earliest dinosaurs to a time when they ultimately dominate."
The area was once a rift valley in the southwest corner of the supercontinent Pangaea. Sediments covered skeletons over a period of five million years, eventually accumulating a thickness of more than 2,000 feet (700 meters).
Volcanoes associated with the nascent Andes Mountains occasionally spewed volcanic ash into the valley, allowing the team to use radioactive elements in the ash layers to determine the age of the sediments.
"Radioisotopes -- our clocks in the rocks -- not only placed the new species in time, about 230 million years ago, but also gave us perspective on the development of this key valley," said Paul Renne, director of the Berkeley Geochronology Center in California. "About five million years of time are represented in these layers, from one end to the other."
In the oldest rocks Eodromaeus lived alongside Eoraptor, a similar-sized, plant-eating dinosaur that Sereno and colleagues discovered in the valley in 1991. Eoraptor's descendants would eventually include the giant, long-necked sauropods. Eodromaeus, with stabbing canine teeth and sharp-clawed grasping hands, is the pint-sized precursor to later meat-eaters called theropods, and eventually to birds.
"We're looking at a snapshot of early dinosaur life. Their storied evolutionary careers are just unfolding, but at this point they're actually quite similar," Sereno said.
Eodromaeus at the root of the dinosaur family tree
Vexing scientific questions at the dawn of the dinosaur era include what gave them an edge over competitors, and how quickly did they rise to dominance? In Eodromaeus' day, other kinds of reptiles outnumbered dinosaurs, such as squat lizard-like rhynchosaurs and mammal-like reptiles. The authors logged thousands of fossils unearthed in the valley to find, as Martinez remarked, that "dinosaurs took their sweet time to dominate the scene."
Their competitors dropped out sequentially over several million years, not at a single horizon in the valley.
In the red cliffs on the far side of the valley, larger plant- and meat-eating dinosaurs had evolved many times the size of Eoraptor and Eodromaeus, but it would be even later when they dominated all land habitats in the succeeding Jurassic and Cretaceous periods.
Story Source:The University of Chicago(Vedio Clip)
The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Chicago.
Prehistoric Bird Used Club-Like Wings as Weapon
ScienceDaily (Jan. 5, 2011) — Long before the knights of medieval Europe wielded flails or martial artists brandished nunchucks, it appears that a flightless prehistoric bird used its own wings as a similar type of weapon in combat.
Paleontologists at Yale University and the Smithsonian Institution have discovered that Xenicibis, a member of the ibis family that lived about ten thousand years ago and was found only in Jamaica, most likely used its specialized wings like a flail, swinging its upper arm and striking its enemies with its thick hand bones.
"No animal has ever evolved anything quite like this," said Nicholas Longrich of Yale, who led the research. "We don't know of any other species that uses its body like a flail. It's the most specialized weaponry of any bird I've ever seen."
As part of the new study, the researchers analyzed a number of recently discovered partial skeletons of Xenicibis and found that the wings were drastically different from anything they'd seen before. "When I first saw it, I assumed it was some sort of deformity," Longrich said. "No one could believe it was actually that bizarre."
The bird, which was the size of a large chicken, is anatomically similar to other members of the ibis family except for its wings, which include thick, curved hand bones unlike those of any other known bird. Xenicibis also had a much larger breastbone and longer wings than most flightless birds. "That was our first clue that the wings were still being used for something," Longrich said.
While other birds are known to punch or hammer one another with their wings, Xenicibis is the only known animal to have used its hands, hinged at the wrist joint, like two baseball bats to swing at and strike its opponents. Although modern day ibises do not strike one another in this fashion, they are very territorial, with mates often fighting other pairs over nesting and feeding rights.
It's also possible that the birds used their club-like wings to defend themselves against other species that might have preyed on the birds' eggs or young. Xenicibis is unusual in that it became flightless even in the midst of a number of predators, including the Jamaican yellow boa, a small extinct monkey and over a dozen birds of prey.
The team found that two of the wing bones in the collection showed evidence of combat, including a fractured hand bone and a centimeter-thick upper arm bone that was broken in half. The damage is proof of the extreme force the birds were able to wield with their specialized wings, Longrich said.
Other authors of the paper, published in the Proceedings of the Royal Society B, include Storrs Olson (National Museum of Natural History, Smithsonian Institution).