Formation of sedimentary layers of white clay, Tamilnadu, India

Fossil site for wood fossils, Tamilnadu, India

Fossil site in Kerala, India

Fossil site in Kerala, India

Fossil wood park maintained by geological survey of India at Tamilnadu

Cretaceous fossil sites india

Fossils in rack:-Cyad

Fossils in rack:-echiniderms

Fossils in rack:-Rastellum sp

Pre-historic seabed, Cretaceous period

Mass Extinctions And The Evolution Of Dinosaurs

March 29th, 2013 Riffin

Dinosaurs survived two mass extinctions and 50 million years before taking over the world and dominating ecosystems, according to new research published this week.

Reporting in Biology Letters, Steve Brusatte, Professor Michael Benton, and colleagues at the University of Bristol show that dinosaurs did not proliferate immediately after they originated, but that their rise was a slow and complicated event, and driven by two mass extinctions.

Illustration of a Tarbosaurus, a cousin of Tyrannosaurus Rex, chasing two Parasaurolophuses. (Credit: iStockphoto/Allan Tooley)

 

“The sheer size of dinosaurs like Tyrannosaurus makes us think there was something special about these animals that preordained them for success right from the beginning,” Brusatte said. “However, our research shows that the rise of dinosaurs was a prolonged and complicated process. It isn’t clear from the data that they would go on to dominate the world until at least 30 million years after they originated.”

 

Importantly, the new research also shows that dinosaurs evolved into all their classic lifestyles  – big predators, long-necked herbivores, etc. – long before they became abundant or diversified into the many different species we know today.

 

Brusatte added: “It just wasn’t a case of dinosaurs exploding onto the scene because of a special adaptation. Rather, they had to wait their turn and evolved in fits and starts before finally dominating their world.”

 

Dinosaurs originated about 230 million years ago and survived the Late Triassic mass extinction (228 million years ago), when some 35 per cent of all living families died out. It was their predecessors dying out during this extinction that allowed herbivorous dinosaurs to expand into the niches they left behind.

 

The rapid expansion of carnivorous and armoured dinosaur groups did not happen until after the much bigger mass extinction some 200 million year ago, at the Triassic-Jurassic boundary. At least half of the species now known to have been living on Earth at that time became extinct, which profoundly affected life on land and in the oceans.

 

Historically the rise of the dinosaurs has been treated as a classic case in which a group evolves key features that allow it to rapidly expand, fill many niches, and out-compete other groups. But Professor Benton said the story isn’t so simplistic: “We argue that the expansion of the dinosaurs took up to 50 million years and was not a simple process that can be explained with broad generalizations.”

New Fossil Species from a Fish-Eat-Fish World When Limbed Animals Evolved

March 28th, 2013 Riffin

Scientists who famously discovered the lobe-finned fish fossil Tiktaalik roseae, a species with some of the clearest evidence of the evolutionary transition from fish to limbed animals, have described another new species of predatory fossil lobe-finned fish fish from the same time and place. By describing more Devonian species, they’re gaining a greater understanding of the “fish-eat-fish world” that drove the evolution of limbed vertebrates.

Dr. Ted Daeschler handles a lower jaw fossil from Holoptychius bergmanni, a lobe-finned fish species from the Devonian Period that he co-discovered and described. (Credit: Drexel University)

Dr. Ted Daeschler handles a lower jaw fossil from Holoptychius bergmanni, a lobe-finned fish species from the Devonian Period that he co-discovered and described. (Credit: Drexel University)

“We call it a ‘fish-eat-fish world,’ an ecosystem where you really needed to escape predation,” said Dr. Ted Daeschler, describing life in the Devonian period in what is now far-northern Canada.

This was the environment where the famous fossil fish species Tiktaalik roseae lived 375 million years ago. This lobe-finned fish, co-discovered by Daeschler, an associate professor at Drexel University in the Department of Biodiversity, Earth and Environmental Science, and associate curator and vice president of the Academy of Natural Sciences of Drexel University, and his colleagues Dr. Neil Shubin and Dr. Farish A. Jenkins, Jr., was first described in Nature in 2006.This species received scientific and popular acclaim for providing some of the clearest evidence of the evolutionary transition from lobe-finned fish to limbed animals, or tetrapods.

Daeschler and his colleagues from the Tiktaalik research, including Academy research associate Dr. Jason Downs, have now described another new lobe-finned fish species from the same time and place in the Canadian Arctic. They describe the new species, Holoptychius bergmanni, in the latest issue of the Proceedings of the Academy of Natural Sciences of Philadelphia.

“We’re fleshing out our knowledge of the community of vertebrates that lived at this important location,” said Downs, who was lead author of the paper. He said describing species from this important time and place will help the scientific community understand the transition from finned vertebrates to limbed vertebrates that occurred in this ecosystem.

“It was a tough world back there in the Devonian. There were a lot of big predatory fish with big teeth and heavy armor of interlocking scales on their bodies,” said Daeschler.

Daeschler said Holoptychius and Tiktaalik were both large predatory fishes adapted to life in stream environments. The two species may have competed with one another for similar prey, although it is possible they specialized in slightly different niches; Tiktaalik‘s tetrapod-like skeletal features made it especially well suited to living in the shallowest waters.

The fossil specimens of Holoptychis bergmanni that researchers used to characterize this new species come from multiple individuals and include lower jaws with teeth, skull pieces including the skull roof and braincase, and parts of the shoulder girdles. The complete fish would have been 2 to 3 feet long when it was alive.

“The three-dimensional preservation of this material is spectacular,” Daeschler said. “For something as old as this, we’ll really be able to collect some good information about the anatomy of these animals.”

The research on Holoptychius bergmanni was led by Downs, a former post-doctoral fellow working with Daeschler who also teaches at Swarthmore College. Other co-authors of the paper with Downs and Daeschler are Dr. Neil Shubin of the University of Chicago, and the late Dr. Farish Jenkins, Jr. of Harvard University, who passed away in 2012.

Honoring a Modern Arctic Explorer and Supporter of Science

The researchers named the new fossil fish species Holoptychius bergmanni in honor of the late Martin Bergmann, former director of the Polar Continental Shelf Program (PCSP), Natural Resources Canada, the organization that provided logistical support during the team’s Arctic research expeditions spanning more than a decade. Bergmann was killed in a plane crash in 2011 shortly after the team’s most recent field season in Nunavut.

“We decided to choose Martin Bergmann to honor him, not ever having met him, but with the understanding that his work with PCSP made great strides in opening the Arctic to researchers,” said Downs. “It’s an invaluable project happening in the Canadian Arctic that’s enabling this type of work to happen.”

Bergmann’s organization assisted the research team with many aspects of expedition logistics including difficult flight operations to carry supplies and research personnel to remote research sites on Ellesemere Island. Daeschler described the pilots as capable of landing a Twin Otter aircraft almost anywhere, as long as the ground was solid — a condition they tested by briefly touching down the airplane and circling back to see if the tires left a deep mark in the mud.

Daeschler and colleagues intend to return to Ellesemere Island for another field expedition in the summer of 2013 to search for fossils in older rocks at a more northerly field site than the one where they discovered T. roseae and H. bergmanni.

A Deeper Look at the Devonian

Daeschler and a different co-author described another new species of Devonian fish in addition to H. bergmanni, in the same issue of the Proceedings of the Academy of Natural Sciences. More information about this new placoderm from Pennsylvania is available at the Drexel News Blog.

Oxygen-Poor ‘Boring’ Ocean Challenged Evolution of Early Life

March 27th, 2013 Riffin

A research team led by biogeochemists at the University of California, Riverside has filled in a billion-year gap in our understanding of conditions in the early ocean during a critical time in the history of life on Earth.

It is now well accepted that appreciable oxygen first accumulated in the atmosphere about 2.4 to 2.3 billion years ago. It is equally well accepted that the build-up of oxygen in the ocean may have lagged the atmospheric increase by well over a billion years, but the details of those conditions have long been elusive because of the patchiness of the ancient rock record.

The period 1.8 to 0.8 billion years ago is of particular interest because it is the essential first chapter in the history of eukaryotes, which are single-celled and multicellular organisms with more complex cellular structures compared to prokaryotes such as bacteria. Their rise was a milestone in the history of life, including that of animals, which first appear around 0.6 to 0.7 billion years ago.

The most interesting thing about the billion-year interval is that despite the rise of oxygen and eukaryotes, the first steps forward were small and remarkably unchanging over a very long period, with oxygen likely remaining low in the atmosphere and ocean and with marine life dominated by bacteria rather than diverse and large populations of more complex eukaryotes. In fact, chemical and biological conditions in this middle age of Earth history were sufficiently static to earn this interval an unflattering nickname — ‘the boring billion.’

But lest it be thought that such a ‘boring’ interval is uninteresting, the extraordinary circumstances required to maintain such biological and chemical stasis for a billion years are worthy of close study, which is what motivated the UC Riverside-led team.

Researchers Chris Reinhard (front) and Noah Planavsky dig into a shale exposure in north China. (Credit: Chu Research Group, Institute of Geology and Geophysics, Chinese Academy of Sciences.)

Researchers Chris Reinhard (front) and Noah Planavsky dig into a shale exposure in north China. (Credit: Chu Research Group, Institute of Geology and Geophysics, Chinese Academy of Sciences.)

By compiling data for metals with very specific and well-known chemical responses to oxygen conditions in the ocean, emphasizing marine sediments from this critical time interval from around the world, the researchers revealed an ancient ocean that was oxygen-free (anoxic) and iron-rich in the deepest waters and hydrogen sulfide-containing over limited regions on the ocean margins.

“Oxygen, by contrast, was limited, perhaps at very low levels, to the surface layers of the ocean,” said Christopher T. Reinhard, the first author of the research paper and a former UC Riverside graduate student. “What’s most unique about our study, however, is that by applying numerical techniques to the data, we were able to place estimates, for the first time, on the full global extent of these conditions. Our results suggest that most of the deep ocean was likely anoxic, compared to something much less than 1 percent today.”

Study results appear online this week in the Proceedings of the National Academy of Sciences.

“A new modeling approach we took allowed us to build on our past work, which was mostly limited to defining very localized conditions in the ancient ocean,” Reinhard said. “The particular strength of the method lies in its ability to define chemical conditions on the seafloor that have long since been lost to plate tectonic recycling.”

Reinhard, now a postdoctoral fellow at Caltech and soon to be an assistant professor at Georgia Institute of Technology, explained that chromium and molybdenum enrichments in ancient organic-rich sedimentary rocks, the focus of the study, actually track the amount of the metals present in ancient seawater. Critically, those concentrations are fingerprints of global ocean chemistry.

Beyond the utility of chromium and molybdenum for tracking oxygen levels in the early ocean, molybdenum is also a bioessential element critical in the biological cycling of nitrogen, a major nutrient in the ocean.

“Molybdenum’s abundance in our ancient rocks is also a direct measure of its availability to early life,” said Timothy W. Lyons, a professor of biogeochemistry at UCR and the principal investigator of the research project. “Our recent results tell us that poor supplies of molybdenum and their impact on nitrogen availability may have limited the rise of oxygen in the ocean and atmosphere and the proliferation of eukaryotic life. There is more to do, certainly, but this is a very tantalizing new read of a chapter in Earth history that is anything but boring.”

WFS Profiles : Barnum Brown (1873-1963)

March 26th, 2013 Riffin
Barnum Brown has been called the greatest “bone hunter” of all time, as well as the last of the great dinosaur hunters.  A forward thinking scientist with a successful career, Brown is most famous for discovering the king of the dinosaurs, which was aptly named Tyrannosaurus rex, or the “king of the tyrant lizards.”   But the discovery of the T. rex was not Brown’s only achievement.  .
Barnum Brown: The Man Who Discovered T. rex

Barnum Brown: The Man Who Discovered T. rex

 

Like Carl Akeley and Roy Chapman Andrews, his colleagues at the American Museum of Natural History, Brown was a real life combination of Indiana Jones and Sherlock Holmes.  He had a sixth sense when it came to discovering dinosaur fossils, and was said to have smelled a fossil prior to sighting any evidence of ancient remains.  He was a man who followed his nose wherever it led him, whether it was the badlands of Canada or the Far East.

Without Brown’s enthusiasm and street-sense, the awesome dinosaurs we take for granted when visiting natural history museums may never have come to be.

Named Barnum, after the co-founder of Barnum and Bailey’s Circus, Brown was a master at mingling scientific adventure with showmanship.  And like his namesake, he was a wheeler-dealer of a businessman and an all around likable chap.  To fund his expensive digs, Brown approached the Sinclair Oil Company and offered to write dinosaur booklets for them to help their sales of “fossil fuel.”  The Sinclair gas stations incorporated a dinosaur for their logo and handed out the booklets that Brown wrote to attract customers.  The oil company was so thrilled with the amount of customers that the logo and dinosaur booklets brought them that they gave Brown enough money to pay for international expeditions and digs at sites all over the world.

 

Picture Brown was known as an eccentric along with being quite a celebrity.  Although he was a brilliant paleontologist, he never fit the image of the stereotypical absent-minded scientist.   In fact, he was a bit of a dandy and often arrived at the site of a dig dressed for a night on the town and wearing a full length fur coat as you can see in the photo on the right of Brown in the Montana badlands.  Sometimes he even wore a top hat. He also loved ballroom dancing and charmed the ladies of his time.

But his claim to fame was bone hunting, so much so that his was sometimes referred to by his peers and fans as Mr. Bones or Mr. Dinosaur.

Born in 1873, Brown began his career in 1897 at the American Museum of Natural History, where he worked as the assistant of Henry Osborne, the museum’s director.  At that time, the museum didn’t have a single dinosaur for its public to view.  Luckily for us, Brown set his mind and heart to the task of filling its rooms with fossils and bones he collected during the sixty-six years he worked there.  By the end of Brown’s successful career as the chief curator of the museum, he had established the largest dinosaur collection in the world and left a legacy that dino lovers everywhere continue to enjoy

In the early 1900s, he discovered the Tyrannosaurus rex in Hell Creek, Montana.  By 1908, he and his assistants had succeeded in finding almost a complete specimen of the T. rex.  This was quite a hit with the public.  Before T. rex, giant carnivorous dinosaurs were more a part of science fiction than science fact.  The public was shocked to know that actual monsters had once roamed the earth!   Since Brown’s first finding, over thirty specimens of T. Rex have been found.

Brown didn’t stop with T. Rex.  He went on to seek dinosaur and mammal fossils in such remote places as the Red Deer River badlands of Alberta.

Never much of a note-taker, Brown described the badlands by the shapes of the rocks.  Although he noted that a “pack” of Tyrannosaurus rexes were found in one particular bonebed, he never wrote down the exact location and took the secret to his grave.  Today’s paleontologists are still searching the rugged crags and crevices of Alberta searching for rocks that were only referenced in Brown’s notes by such vague names as the “Widow.”

Armed with ample funding from oil companies, Brown spent his life roaming the globe in search of previously unknown dinosaurs.  He found quite a few!   He often named them according to a part of their anatomy which separated them from their comrades.  Most of the names of the dinosaurs that Barnum Brown found were later changed, probably to the dismay of the eccentric dino hunter.

source: Las Vegas Natural History Museum site

Megavolcanoes Tied to Pre-Dinosaur Mass Extinction: Apparent Sudden Climate Shift Could Have Analog Today

March 25th, 2013 Riffin

Scientists examining evidence across the world from New Jersey to North Africa say they have linked the abrupt disappearance of half of earth’s species 200 million years ago to a precisely dated set of gigantic volcanic eruptions. The eruptions may have caused climate changes so sudden that many creatures were unable to adapt — possibly on a pace similar to that of human-influenced climate warming today. The extinction opened the way for dinosaurs to evolve and dominate the planet for the next 135 million years, before they, too, were wiped out in a later planetary cataclysm.

In recent years, many scientists have suggested that the so-called End-Triassic Extinction and at least four other known past die-offs were caused at least in part by mega-volcanism and resulting climate change. However, they were unable to tie deposits left by eruptions to biological crashes closely in time. This study provides the tightest link yet, with a newly precise date for the ETE–201,564,000 years ago, exactly the same time as a massive outpouring of lava. “This may not quench all the questions about the exact mechanism of the extinction itself. However, the coincidence in time with the volcanism is pretty much ironclad,” said coauthor Paul Olsen, a geologist at Columbia University’s Lamont-Doherty Earth Observatory who has been investigating the boundary since the 1970s.

Along sea cliffs in southern England, geologist Paul Olsen of Columbia University's Lamont-Doherty Earth Observatory samples rocks from near the 201,564,000-year Triassic extinction boundary. (Credit: Kevin Krajick/Earth Institute)

Along sea cliffs in southern England, geologist Paul Olsen of Columbia University’s Lamont-Doherty Earth Observatory samples rocks from near the 201,564,000-year Triassic extinction boundary. (Credit: Kevin Krajick/Earth Institute)

The new study unites several pre-existing lines of evidence by aligning them with new techniques for dating rocks. Lead author Terrence Blackburn (then at Massachusetts Institute of Technology; now at the Carnegie Institution) used the decay of uranium isotopes to pull exact dates from basalt, a rock left by eruptions. The basalts analyzed in the study all came from the Central Atlantic Magmatic Province (CAMP), a series of huge eruptions known to have started around 200 million years ago, when nearly all land was massed into one huge continent. The eruptions spewed some 2.5 million cubic miles of lava in four sudden spurts over a 600,000-year span, and initiated a rift that evolved into the Atlantic Ocean; remnants of CAMP lavas are found now in North and South America, and North Africa. The scientists analyzed samples from what are now Nova Scotia, Morocco and the New York City suburbs. (Olsen hammered one from a road cut in the Hudson River Palisades, about 1,900 feet from the New Jersey side of the George Washington Bridge.)

Previous studies have suggested a link between the CAMP eruptions and the extinction, but other researchers’ dating of the basalts had a margin of error of 1 to 3 million years. The new margin of error is only a few thousand years — in geology, an eye blink. Blackburn and his colleagues showed that the eruption in Morocco was the earliest, with ones in Nova Scotia and New Jersey coming about 3,000 and 13,000 years later, respectively. Sediments below that time contain pollen, spores and other fossils characteristic of the Triassic era; in those above, the fossils disappear. Among the creatures that vanished were eel-like fish called conodonts, early crocodilians, tree lizards and many broad-leaved plants. The dating is further strengthened by a layer of sediment just preceding the extinction containing mineral grains providing evidence of one of earth’s many periodic reversals of magnetic polarity. This particular reversal, labeled E23r, is consistently located just below the boundary, making it a convenient marker, said coauthor Dennis Kent, a paleomagnetism expert who is also at Lamont-Doherty. With the same layers found everywhere the researchers have looked so far, the eruptions “had to be a hell of an event,” said Kent.

The third piece of chronological evidence is the sedimentary layers themselves. Sedimentary rocks cannot be dated directly — one reason why the timing of the extinction has been hard to nail. Olsen and some others have long contended that Earth’s precession — a cyclic change in the orientation of the axis toward the sun and resulting temperature changes — consistently created layers reflecting the alternate filling and drying of large lake basins on a fairly steady 20,000-year schedule. This idea is well accepted for more recent time, but many scientists have had doubts about whether it could be applied much farther back. By correlating the precisely dated basalts with surrounding sedimentary layers, the new study shows that precession operated pretty much the same way then, allowing dates with a give or take of 20,000 years to be assigned to most sediments holding fossils, said Olsen.

Olsen has painstakingly cataloged the layers around the time of the End Triassic, and the initial phase of the extinction occurs in just one layer — meaning the event took 20,000 years at most. But, he said, “it could have taken much less. This is the level of resolution we have now, but it’s the ‘less’ part that is the more important, and that’s what we are working on now.”

Many scientists assume that giant eruptions would have sent sulfurous particles into the air that darkened the skies, creating a multi-year winter that would have frozen out many creatures. A previous study by Kent and Rutgers University geochemist Morgan Schaller has also shown that each pulse of volcanism doubled the air’s concentration of carbon dioxide — a major component of volcanic gases. Following the cold pulses, the warming effects of this greenhouse gas would have lasted for millennia, wiping out creatures that could not take too much heat. (It was already quite hot to begin with at that time; even pre-eruption CO2 levels were higher than those of today.) Fossils show that heat-sensitive plants especially suffered; there is also evidence that the increased CO2 caused chemical reactions that made the oceans more acidic, causing populations of shell-building creatures to collapse. As if this were not enough, there is also some evidence that a large meteorite hit Earth at the time of the extinction–but that factor seems far less certain. A much stronger case has been made for the extinction of the dinosaurs by a meteorite some 65 million years ago — an event that opened the way for the evolution and dominance of mammals, including human beings. Volcanism may have been involved in that extinction as well, with the meteorite delivering the final blow.)

The End Triassic was the fourth known global die-off; the extinction of the dinosaurs was the fifth. Today, some scientists have proposed that we are on the cusp of a sixth, humanmade, extinction. Explosive human population growth, industrial activity and exploitation of natural resources are rapidly pushing many species off the map. Burning of fossil fuels in particular has had an effect, raising the air’s CO2 level more than 40 percent in just 200 years — a pace possibly as fast, or faster, than that of the End Triassic. Resulting temperatures increases now appear to be altering ecosystems; and CO2 entering seawater is causing what could be the fastest ongoing acidification of the oceans for at least the last 300 million years, according to a 2012 study. “In some ways, the End Triassic Extinction is analogous to today,” said Blackburn. “It may have operated on a similar time scale. Much insight on the possible future impact of doubling atmospheric CO2 on global temperatures, ocean acidity and life on earth may be gained by studying the geologic record.”

Paul Renne, a researcher at the Berkeley Geochronology Center in California, who studies the End Triassic but was not involved in the Science paper, said the study was “part of a growing pattern in which we see that the major ecosystem crises were triggered” by volcanism. He said the new data “make the case stronger than it was. … The pendulum continues to swing in favor of that idea.” Of the actual mechanism that killed creatures, he said climate change was the most popular suspect. But, he added, “We still don’t have any way yet of knowing exactly how much CO2 was put into the atmosphere at that time, and what it did. If we did, we would then be able to say to people, ‘Look folks, this is what we’re facing now, and here’s what we have to do about it. But we don’t know that yet.”

Structural Extremes in a Cretaceous Dinosaur

March 24th, 2013 Riffin

Fossils of the Early Cretaceous dinosaur, Nigersaurus taqueti, document for the first time the cranial anatomy of a rebbachisaurid sauropod. Its extreme adaptations for herbivory at ground-level challenge current hypotheses regarding feeding function and feeding strategy among diplodocoids, the larger clade of sauropods that includes Nigersaurus. We used high resolution computed tomography, stereolithography, and standard molding and casting techniques to reassemble the extremely fragile skull. Computed tomography also allowed us to render the first endocast for a sauropod preserving portions of the olfactory bulbs, cerebrum and inner ear, the latter permitting us to establish habitual head posture. To elucidate evidence of tooth wear and tooth replacement rate, we used photographic-casting techniques and crown thin sections, respectively. To reconstruct its 9-meter postcranial skeleton, we combined and size-adjusted multiple partial skeletons. Finally, we used maximum parsimony algorithms on character data to obtain the best estimate of phylogenetic relationships among diplodocoid sauropods. Nigersaurus taqueti shows extreme adaptations for a dinosaurian herbivore including a skull of extremely light construction, tooth batteries located at the distal end of the jaws, tooth replacement as fast as one per month, an expanded muzzle that faces directly toward the ground, and hollow presacral vertebral centra with more air sac space than bone by volume. A cranial endocast provides the first reasonably complete view of a sauropod brain including its small olfactory bulbs and cerebrum. Skeletal and dental evidence suggests that Nigersaurus was a ground-level herbivore that gathered and sliced relatively soft vegetation, the culmination of a low-browsing feeding strategy first established among diplodocoids during the Jurassic.

Partial skeleton of Nigersaurus taqueti (MNN GAD517) discovered during the 2000 Expedition to Niger. Expedition member G. Lyon is seated inside the curve of the proximal caudal vertebrae of a skeleton planed flat by wind-blown sand at a site in Gadoufaoua, Ténéré Desert, Niger (photo by M. Hettwer).

Partial skeleton of Nigersaurus taqueti (MNN GAD517) discovered during the 2000 Expedition to Niger. Expedition member G. Lyon is seated inside the curve of the proximal caudal vertebrae of a skeleton planed flat by wind-blown sand at a site in Gadoufaoua, Ténéré Desert, Niger (photo by M. Hettwer).

The diagram is based on strict consensus of five minimum-length trees using 13 ingroup taxa and 102 unordered characters (CI = 0.76; RI = 0.78) (Text S5). Scaled icons represent a diplodocid (Apatosaurus) [11], dicraeosaurid (Dicraeosaurus) [51], and a rebbachisaurid (Nigersaurus). Geographic distributions include Laurasian diplodocoids (western North America—Apatasaurus, Diplodocus, Suuwassea; Europe—Histriasaurus, Spanish rebbachisaurid) and Gondwanan diplodocoids (South America—Cathartesaura, Limaysaurus, Zapalasaurus; Africa—Rebbachisaurus, Nigersaurus). Temporal boundaries based on a recent timescale [52]. Color scheme: Laurasia (orange); Gondwana (blue); North America (solid orange); Europe (striped orange); South America (blue); Africa (striped blue). doi:10.1371/journal.pone.0001230.g004

The diagram is based on strict consensus of five minimum-length trees using 13 ingroup taxa and 102 unordered characters (CI = 0.76; RI = 0.78) (Text S5). Scaled icons represent a diplodocid (Apatosaurus) [11], dicraeosaurid (Dicraeosaurus) [51], and a rebbachisaurid (Nigersaurus). Geographic distributions include Laurasian diplodocoids (western North America—Apatasaurus, Diplodocus, Suuwassea; Europe—Histriasaurus, Spanish rebbachisaurid) and Gondwanan diplodocoids (South America—Cathartesaura, Limaysaurus, Zapalasaurus; Africa—Rebbachisaurus, Nigersaurus). Temporal boundaries based on a recent timescale [52]. Color scheme: Laurasia (orange); Gondwana (blue); North America (solid orange); Europe (striped orange); South America (blue); Africa (striped blue).
doi:10.1371/journal.pone.0001230.g004

Citation: Sereno PC, Wilson JA, Witmer LM, Whitlock JA, Maga A, et al. (2007) Structural Extremes in a Cretaceous Dinosaur. PLoS ONE 2(11): e1230. doi:10.1371/journal.pone.0001230

Academic Editor: Tom Kemp, University of Oxford, United Kingdom

 

 

 

Fossil Bird Study On Extinction Patterns Could Help Today’s Conservation Efforts

March 23rd, 2013 Riffin

A new University of Florida study of nearly 5,000 Haiti bird fossils shows contrary to a commonly held theory, human arrival 6,000 years ago didn’t cause the island’s birds to die simultaneously.

Although many birds perished or became displaced during a mass extinction event following the first arrival of humans to the Caribbean islands, fossil evidence shows some species were more resilient than others. The research provides range and dispersal patterns from A.D. 600 to 1600 that may be used to create conservation plans for tropical mountainous regions, some of the most threatened habitats worldwide. Understanding what caused recent extinctions — whether direct habitat loss or introduction of invasive species — helps researchers predict future ecological impacts. The study was published online in The , March 12 and is scheduled to appear in the journal’s print edition in July.

Florida Museum of Natural History ornithologist David Steadman displays fossils of an undescribed, extinct new species of woodcock from Hispaniola. In a study published online March 12 in The Holocene, Steadman analyzed nearly 5,000 fossils from the Trouing Jean Paul site in southeast Haiti to better understand range and dispersal patterns, a tool that may be used to create more effective conservation plans. The extinct woodcock was one of the most common bird species at the site. (Credit: University of Florida by Kristen Grace)

Florida Museum of Natural History ornithologist David Steadman displays fossils of an undescribed, extinct new species of woodcock from Hispaniola. In a study published online March 12 in The Holocene, Steadman analyzed nearly 5,000 fossils from the Trouing Jean Paul site in southeast Haiti to better understand range and dispersal patterns, a tool that may be used to create more effective conservation plans. The extinct woodcock was one of the most common bird species at the site. (Credit: University of Florida by Kristen Grace)

“People arrive about 6,000 years ago and within a millennium or two, you lose the big, spectacular critters — the ground sloths, the monkeys, the biggest rodents and some of the big extinct birds, like giant owls and eagles,” said lead author David Steadman, ornithology curator at the Florida Museum of Natural History on the UF campus. “We have some bird species from our fossil site that, from a modern standpoint, are just as extinct as the others, but in fact, they almost were able to survive longer. That helps give us a gauge on what the future might bring.”

Researchers used comparisons with modern bones to identify 23 species from the 4,857 bird fossils excavated from Trouing Jean Paul, a cave in southeast Haiti at an elevation of about 6,000 feet. The most common bird species include the Zenaida Dove, the Black Swift, the Least Pauraque, the Hispaniolan woodpecker and a new, undescribed extinct woodcock in the genus Scolopax. Researchers believe the woodcock became extinct between A.D. 1350 and 1800, surviving the first arrival of the Amerindians 6,000 years ago, but dying off following the arrival of Europeans and African peoples in 1492, Steadman said.

“When you take a look at what could’ve caused this, it really does just keep pointing to humans,” Steadman said. “I just think it’s habitat loss from people and introduction of non-native, invasive plants and animals. It’s the same thing we’re dealing with in Florida now — who knows what the pythons are going to wipe out in the Everglades.”

Researchers radiocarbon-dated six individual bones from the extinct woodcock to determine the site’s age. Because the locality also includes fossils of frogs, lizards, snakes, bats and rodents, in addition to the Common Barn Owl and Ashy-faced Owl, it was likely a roost where owls deposited boney pellets of their prey, scientists said.

Of the present-day species found at the site, as many as one-third are considered threatened today and four of the 23 total species are no longer found in the area. Their predominant habitat was pine forests, which are mostly disturbed today or entirely cut down for agriculture. The Least Pauraque, a type of nightjar, is now an endangered species that lives in an extremely localized area, Steadman said.

“This gives us some evidence of how drastic the range contraction was of this species — the Least Pauraque not only lived in the mountains, it was common there,” Steadman said. “Within 1,000 years, it’s lost most of its range and most of its population. From the standpoint of evolution, if we want that species to ever have the opportunity to evolve through time, we need to be concerned with time intervals that are measured in centuries and millennia, not just decades.”

Jim Mead, professor and chair of the department of geosciences at East Tennessee State University, said the research is important because the direct radiocarbon dating represents a much later time period than the arrival of the first Amerindians.

“What Steadman is finding, more often than not, is that we as people bring in other things with us and indirectly wipe out other animals,” said Mead, who was not involved with the study. “He’s providing background data and I think that’s critical to Hispaniola because you have two countries on that island and they’re quite different culturally and economically, so those countries are going to play different games on the local fauna.”

Mead said it is also significant that Trouing Jean Paul occurs at a high elevation, where human or climate pressures could result in animals finding a “refugia” upslope.

“Typically, a lot of sites are found in lower elevation, or we go to the lower elevations to look at localities we work on,” Mead said. “But Dave is saying, ‘Why don’t we look at these other areas that haven’t really been examined?’ This one cave is a critical one for that. It gives us a 3-D look at environments on an island.”

Oona Takano, who helped sort and identify the specimens as a UF undergraduate student, is a study co-author.

Scientists Discover ‘Lubricant’ for Earth’s Tectonic Plates: Hidden Magma Layer Could Play Role in Earthquakes

March 21st, 2013 Riffin

Scientists at Scripps Institution of Oceanography at UC San Diego have found a layer of liquefied molten rock in Earth’s mantle that may be acting as a lubricant for the sliding motions of the planet’s massive tectonic plates. The discovery may carry far-reaching implications, from solving basic geological functions of the planet to a better understanding of volcanism and earthquakes.

The scientists discovered the magma layer at the Middle America trench offshore Nicaragua. Using advanced seafloor electromagnetic imaging technology pioneered at Scripps, the scientists imaged a 25-kilometer- (15.5-mile-) thick layer of partially melted mantle rock below the edge of the Cocos plate where it moves underneath Central America.

The orange colored area enclosed by a dashed line denotes a magma layer that scientists believe is facilitating the motion of the Cocos plate off Nicaragua. The blue areas represent the Cocos plate sliding across the mantle and eventually diving beneath the Central American continent, while the black dots signify earthquake locations. The discovery was made by analyzing data collected by an array of seafloor electromagnetic instruments, shown as inverted triangles. (Credit: Image courtesy of University of California – San Diego)

The discovery is reported in the March 21 issue of the journal Nature by Samer Naif, Kerry Key, and Steven Constable of Scripps, and Rob Evans of Woods Hole Oceanographic Institution.

The new images of magma were captured during a 2010 expedition aboard the U.S. Navy-owned and Scripps-operated research vessel Melville. After deploying a vast array of seafloor instruments that recorded natural electromagnetic signals to map features of the crust and mantle, the scientists realized they found magma in a surprising place.

“This was completely unexpected,” said Key, an associate research geophysicist in the Cecil H. and Ida M. Green Institute of Geophysics and Planetary Physics at Scripps. “We went out looking to get an idea of how fluids are interacting with plate subduction, but we discovered a melt layer we weren’t expecting to find at all — it was pretty surprising.”

For decades scientists have debated the forces and circumstances that allow the planet’s tectonic plates to slide across Earth’s mantle. Studies have shown that dissolved water in mantle minerals results in a more ductile mantle that would facilitate tectonic plate motions, but for many years clear images and data required to confirm or deny this idea were lacking.

“Our data tell us that water can’t accommodate the features we are seeing,” said Naif, a Scripps graduate student and lead author of the paper. “The information from the new images confirms the idea that there needs to be some amount of melt in the upper mantle and that’s really what’s creating this ductile behavior for plates to slide.”

The marine electromagnetic technology employed in the study was originated by Charles “Chip” Cox, an emeritus professor of oceanography at Scripps, and in recent years further advanced by Constable and Key. Since 2000 they have been working with the energy industry to apply this technology to map offshore oil and gas reservoirs.

The researchers say their results will help geologists better understand the structure of the tectonic plate boundary and how that impacts earthquakes and volcanism.

“One of the longer-term implications of our results is that we are going to understand more about the plate boundary, which could lead to a better understanding of earthquakes,” said Key.

The researchers are now seeking to find the source that supplies the magma in the newly discovered layer.

The National Science Foundation and the Seafloor Electromagnetic Methods Consortium at Scripps supported the research.

Sea Floor Earthquake Zones Can Act Like a ‘Magnifying Lens’ Strengthening Tsunamis Beyond What Was Through Possible

March 20th, 2013 Riffin

The earthquake zones off of certain coasts — like those of Japan and Java — make them especially vulnerable to tsunamis, according to a new study. They can produce a focusing point that creates massive and devastating tsunamis that break the rules for how scientists used to think tsunamis work.

Until now, it was largely believed that the maximum tsunami height onshore could not exceed the depth of the seafloor. But new research shows that when focusing occurs, that scaling relationship breaks down and flooding can be up to 50 percent deeper with waves that do not lose height as they get closer to shore.

“It is as if one used a giant magnifying lens to focus tsunami energy,” said Utku Kanoglu, professor at the Middle East Technical University and senior author of the study. “Our results show that some shorelines with huge earthquake zones just offshore face a double whammy: not only they are exposed to the tsunamis, but under certain conditions, focusing amplifies these tsunamis far more than shoaling and produces devastating effects.”

The team observed this effect both in Northern Japan, which was struck by the Tohoku tsunami of 2011, and in Central Java, which was struck by a tsunami in 2006.

“We are still trying to understand the implications,” said Costas Synolakis, director of the Tsunami Research Center at the USC Viterbi School of Engineering and a co-author of the study. “But it is clear that our findings will make it easier to identify locales that are tsunami magnets, and thus help save lives in future events.”

During an earthquake, sections of the sea floor lift up while others sink. This creates tsunamis that propagate trough-first in one direction and crest-first in the other. The researchers discovered that on the side of the earthquake zone where the wave propagates trough-first, there is a location where focusing occurs — strengthening it before it hits the coastline with an unusual amount of energy that is not seen by the crest-first wave. Based on the shape, location, and size of the earthquake zone, that focal point can concentrate the tsunami’s power right on to the coastline.

In addition, before this analysis, it was thought that tsunamis usually decrease in height continuously as they move away from where they are created and grow close to shore, just as wind waves do. The study’s authors instead suggest that the crest of the tsunami remains fairly intact close to the source.

“While our study does not preclude that other factors may help tsunamis overgrow, we now know when to invoke exotic explanations for unusual devastation: only when the basic classic wave theory we use does not predict focusing, or if the focusing is not high enough to explain observations,” said Vasily Titov, a researcher at NOAA’s Pacific Marine Environmental Laboratory and study co-author.

Animation of a formation and focusing of a Tsunami: http://www.youtube.com/watch?v=BUS4dsBf8BI&feature=youtu.be

A New Snake Skull from the Paleocene of Bolivia Sheds Light on the Evolution of Macrostomatans

March 19th, 2013 Riffin

Macrostomatan snakes, one of the most diverse extant clades of squamates, display an impressive arsenal of cranial features to consume a vast array of preys. In the absence of indisputable fossil representatives of this clade with well-preserved skulls, the mode and timing of these extraordinary morphological novelties remain obscure. Here, we report the discovery of Kataria anisodonta n. gen. n. sp., a macrostomatan snake recovered in the Early Palaeocene locality of Tiupampa, Bolivia. The holotype consists of a partial, minute skull that exhibits a combination of booid and caenophidian characters, being the presence of an anisodont dentition and diastema in the maxilla the most distinctive trait. Phylogenetic analysis places Kataria basal to the Caenophidia+Tropidophiidae, and represents along with bolyeriids a distinctive clade of derived macrostomatans. The discovery of Kataria highlights the morphological diversity in the maxilla among derived macrostomatans, demonstrating the relevance of maxillary transformations in the evolution of this clade. Kataria represents the oldest macrostomatan skull recovered, revealing that the diversification of macrostomatans was well under way in early Tertiary times. This record also reinforces the importance of Gondwanan territories in the history of snakes, not only in the origin of the entire group but also in the evolution of ingroup clades.

The skull of Kataria anisodonta (MHNC 13323). Photographs and half-tone drawings in (A) left lateral, (B) right lateral, (C) dorsal and (D) ventral views. Dotted areas indicate matrix. chp, choanal process; ec, ectopterygoid; fr, frontal; ip, interchoanal process; mx, maxilla; mxp, maxillary process; op, optic foramen; p, parietal; pf, prefrontal; pl, palatine; plp, palatine process; po, postorbital; ps, parasphenoid; pt, pterygoid; sm, septomaxilla; v, vomer. doi:10.1371/journal.pone.0057583.g001

The skull of Kataria anisodonta (MHNC 13323).
Photographs and half-tone drawings in (A) left lateral, (B) right lateral, (C) dorsal and (D) ventral views. Dotted areas indicate matrix. chp, choanal process; ec, ectopterygoid; fr, frontal; ip, interchoanal process; mx, maxilla; mxp, maxillary process; op, optic foramen; p, parietal; pf, prefrontal; pl, palatine; plp, palatine process; po, postorbital; ps, parasphenoid; pt, pterygoid; sm, septomaxilla; v, vomer.
doi:10.1371/journal.pone.0057583.g001

 

Details of the holotype specimen of Kataria anisodonta. (A) frontal view of the partial skull; (B) dorsolateral view of the left orbit; (C) ventral view of the palatal region; (D) scanning electron microscope image of the rear maxillary region. chp, choanal process; dot, ductus for olfactory tract; ec, ectopterygoid; fr, frontal; ip, interchoanal process; mfr, medial frontal flange; mx, maxilla; mxp, maxillary process; op, optic foramen; p, parietal; pf, prefrontal; pl, palatine; plp, palatine process; po, postorbital; ps, parasphenoid; pt, pterygoid; sm, septomaxilla; v, vomer. doi:10.1371/journal.pone.0057583.g002

Details of the holotype specimen of Kataria anisodonta.
(A) frontal view of the partial skull; (B) dorsolateral view of the left orbit; (C) ventral view of the palatal region; (D) scanning electron microscope image of the rear maxillary region. chp, choanal process; dot, ductus for olfactory tract; ec, ectopterygoid; fr, frontal; ip, interchoanal process; mfr, medial frontal flange; mx, maxilla; mxp, maxillary process; op, optic foramen; p, parietal; pf, prefrontal; pl, palatine; plp, palatine process; po, postorbital; ps, parasphenoid; pt, pterygoid; sm, septomaxilla; v, vomer.
doi:10.1371/journal.pone.0057583.g002

 

Lateral view of maxillary bones showing differences in tooth row morphology of macrostomatan snakes. (A) the boid Eunectes notaeus, (b) the bolyeriid Casarea dussumieri [44], (C) Kataria anisodonta and (D) the opistoglyphous colubroid Philodryas trilineatus. Not to scale. amx, anterior maxilla; ecp, ectopterygoid process; plp, palatine process; pmx, posterior maxilla; soo, suborbital ossification. doi:10.1371/journal.pone.0057583.g003

Lateral view of maxillary bones showing differences in tooth row morphology of macrostomatan snakes.
(A) the boid Eunectes notaeus, (b) the bolyeriid Casarea dussumieri [44], (C) Kataria anisodonta and (D) the opistoglyphous colubroid Philodryas trilineatus. Not to scale. amx, anterior maxilla; ecp, ectopterygoid process; plp, palatine process; pmx, posterior maxilla; soo, suborbital ossification.
doi:10.1371/journal.pone.0057583.g003

Citation: Scanferla A, Zaher H, Novas FE, de Muizon C, Céspedes R (2013) A New Snake Skull from the Paleocene of Bolivia Sheds Light on the Evolution of Macrostomatans. PLoS ONE 8(3): e57583. doi:10.1371/journal.pone.0057583

Editor: Richard J. Butler, Ludwig-Maximilians-Universität München, Germany

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