WFS

Formation of sedimentary layers of white clay, Tamilnadu, India

Fossil site for wood fossils, Tamilnadu, 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

Birth of Earth’s Continents: New Research Points to Crust Stacking, Rather Than Upwelling of Hot Material

September 19th, 2013

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New research led by a University of Calgary geophysicist provides strong evidence against continent formation above a hot mantle plume, similar to an environment that presently exists beneath the Hawaiian Islands.

The analysis, published this month in Nature Geoscience, indicates that the nuclei of Earth’s continents formed as a byproduct of mountain-building processes, by stacking up slabs of relatively cold oceanic crust. This process created thick, strong ‘keels’ in Earth’s mantle that supported the overlying crust and enabled continents to form.

This computer simulation shows density difference of the mantle, compared to an oceanic reference, starting from a cooler initial state. Density is controlled by mantle composition as well as slowly cooling temperature; a keel of low-density material extending to about 260 km depth on the left side (x < 600 km) provides buoyancy that prevents continents from being subducted (‘recycled’ into the deep Earth). Graph on the top shows a computed elevation model. (Credit: David Eaton, University of Calgary)

The scientific clues leading to this conclusion derived from computer simulations of the slow cooling process of continents, combined with analysis of the distribution of diamonds in the deep Earth.

The Department of Geoscience’s Professor David Eaton developed computer software to enable numerical simulation of the slow diffusive cooling of Earth’s mantle over a time span of billions of years.

Working in collaboration with former graduate student, Assistant Professor Claire Perry from the Universite du Quebec a Montreal, Eaton relied on the geological record of diamonds found in Africa to validate his innovative computer simulations.

“For the first time, we are able to quantify the thermal evolution of a realistic 3D Earth model spanning billions of years from the time continents were formed,” states Perry.

Mantle plumes consist of an upwelling of hot material within Earth’s mantle. Plumes are thought to be the cause of some volcanic centres, especially those that form a linear volcanic chain like Hawaii. Diamonds, which are generally limited to the deepest and oldest parts of the continental mantle, provide a wealth of information on how the host mantle region may have formed.

“Ancient mantle keels are relatively strong, cold and sometimes diamond-bearing material. They are known to extend to depths of 200 kilometres or more beneath the ancient core regions of continents,” explains Professor David Eaton. “These mantle keels resisted tectonic recycling into the deep mantle, allowing the preservation of continents over geological time and providing suitable environments for the development of the terrestrial biosphere.”

His method takes into account important factors such as dwindling contribution of natural radioactivity to the heat budget, and allows for the calculation of other properties that strongly influence mantle evolution, such as bulk density and rheology (mechanical strength).

“Our computer model emerged from a multi-disciplinary approach combining classical physics, mathematics and computer science,” explains Eaton. “By combining those disciplines, we were able to tackle a fundamental geoscientific problem, which may open new doors for future research.”

This work provides significant new scientific insights into the formation and evolution of continents on Earth.

‘Highway from Hell’ Fueled Costa Rican Volcano

September 18th, 2013

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If some volcanoes operate on geologic timescales, Costa Rica’s Irazú had something of a short fuse. In a new study in the journal Nature, scientists suggest that the 1960s eruption of Costa Rica’s largest stratovolcano was triggered by magma rising from the mantle over a few short months, rather than thousands of years or more, as many scientists have thought. The study is the latest to suggest that deep, hot magma can set off an eruption fairly quickly, potentially providing an extra tool for detecting an oncoming volcanic disaster.

“If we had had seismic instruments in the area at the time we could have seen these deep magmas coming,” said the study’s lead author, Philipp Ruprecht, a volcanologist at Columbia University’s Lamont-Doherty Earth Observatory. “We could have had an early warning of months, instead of days or weeks.”

Towering more than 10,000 feet and covering almost 200 square miles, Irazú erupts about every 20 years or less, with varying degrees of damage. When it awakened in 1963, it erupted for two years, killing at least 20 people and burying hundreds of homes in mud and ash. Its last eruption, in 1994, did little damage.

Volcán Irazú (Costa Rica). If some volcanoes operate on geologic timescales, Costa Rica’s Irazú had something of a short fuse. (Credit: © xevibp / Fotolia)

Irazú sits on the Pacific Ring of Fire, where oceanic crust is slowly sinking beneath the continents, producing some of earth’s most spectacular fireworks. Conventional wisdom holds that the mantle magma feeding those eruptions rises and lingers for long periods of time in a mixing chamber several miles below the volcano. But ash from Irazú’s prolonged explosion is the latest to suggest that some magma may travel directly from the upper mantle, covering more than 20 miles in a few months.

“There has to be a conduit from the mantle to the magma chamber,” said study co-author Terry Plank, a geochemist at Lamont-Doherty. “We like to call it the highway from hell.”

Their evidence comes from crystals of the mineral olivine separated from the ashes of Irazú’s 1963-1965 eruption, collected on a 2010 expedition to the volcano. As magma rising from the mantle cools, it forms crystals that preserve the conditions in which they formed. Unexpectedly, Irazú’s crystals revealed spikes of nickel, a trace element found in the mantle. The spikes told the researchers that some of Irazú’s erupted magma was so fresh the nickel had not had a chance to diffuse.

“The study provides one more piece of evidence that it’s possible to get magma from the mantle to the surface in very short order,” said John Pallister, who heads the U.S. Geological Survey (USGS) Volcano Disaster Assistance Program in Vancouver, Wash. “It tells us there’s a potentially shorter time span we need to worry about.”

Deep, fast-rising magma has been linked to other big events. In 1991, Mount Pinatubo in the Philippines spewed so much gas and ash into the atmosphere that it cooled Earth’s climate. In the weeks before the eruption, seismographs recorded hundreds of deep earthquakes that USGS geologist Randall White later attributed to magma rising from the mantle-crust boundary. In 2010, a chain of eruptions at Iceland’s Eyjafjallajökull volcano that caused widespread flight cancellations also indicated that some magma was coming from down deep. Small earthquakes set off by the eruptions suggested that the magma in Eyjafjallajökull’s last two explosions originated 12 miles and 15 miles below the surface, according to a 2012 study by University of Cambridge researcher Jon Tarasewicz in Geophysical Research Letters.

Volcanoes give off many warning signs before a blow-up. Their cones bulge with magma. They vent carbon dioxide and sulfur into the air, and throw off enough heat that satellites can detect their changing temperature. Below ground, tremors and other rumblings can be detected by seismographs. When Indonesia’s Mount Merapi roared to life in late October 2010, officials led a mass evacuation later credited with saving as many as 20,000 lives.

Still, the forecasting of volcanic eruptions is not an exact science. Even if more seismographs could be placed along the flanks of volcanoes to detect deep earthquakes, it is unclear if scientists would be able to translate the rumblings into a projected eruption date. Most problematically, many apparent warning signs do not lead to an eruption, putting officials in a bind over whether to evacuate nearby residents.

“[Several months] leaves a lot of room for error,” said Erik Klemetti, a volcanologist at Denison University. “In volcanic hazards you have very few shots to get people to leave.”

Scientists may be able to narrow the window by continuing to look for patterns between eruptions and the earthquakes that precede them. The Nature study also provides a real-world constraint for modeling how fast magma travels to the surface. “If this interpretation is correct, you start having a speed limit that your models of magma transport have to catch,” said Tom Sisson, a USGS volcanologist based at Menlo Park, Calif.

Olivine minerals with nickel spikes similar to Irazú’s have been found in the ashes of arc volcanoes in Mexico, Siberia and the Cascades of the U.S. Pacific Northwest, said Lamont geochemist Susanne Straub, whose ideas inspired the study. “It’s clearly not a local phenomenon,” she said. The researchers are currently analyzing crystals from past volcanic eruptions in Alaska’s Aleutian Islands, Chile and Tonga, but are unsure how many will bear Irazú’s fast-rising magma signature. “Some may be capable of producing highways from hell and some may not,” said Ruprecht.

Extreme Life Forms: Life Found in the Sediments of an Antarctic Subglacial Lake for the First Time

September 17th, 2013

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Evidence of diverse life forms dating back nearly a hundred thousand years has been found in subglacial lake sediments by a group of British scientists.

Drilling. (Credit: Image courtesy of British Antarctic Survey)

The possibility that extreme life forms might exist in the cold and dark lakes hidden kilometres beneath the Antarctic ice sheet has fascinated scientists for decades.

However, direct sampling of these lakes in the interior of Antarctica continues to present major technological challenges. Recognising this, scientists from the British Antarctic Survey (BAS), and the Universities of Northumbria and Edinburgh have been searching around the retreating margins of the ice sheet for subglacial lakes that are becoming exposed for the first time since they were buried more than 100,000 years ago.

This is because parts of the ice sheet are melting and retreating at unprecedented rates as the temperature rises at the poles.

The group targeted Lake Hodgson on the Antarctic Peninsula which was covered by more than 400 m of ice at the end of the last Ice Age, but is now considered to be an emerging subglacial lake, with a thin covering of just 3-4 metres of ice.

Drilling through the ice they used clean coring techniques to delve into the sediments at the bottom of the lake which is 93 metres deep and approximately 1.5 km long by 1.5 km wide.

The lake was thought to be a harsh environment for any form of life but the layers of mud at the bottom of the lake represent a time capsule storing the DNA of the microbes which have lived there throughout the millennia. The top few centimetres of the core contained current and recent organisms which inhabit the lake but once the core reached 3.2 m deep the microbes found most likely date back nearly 100,000 years.

Lead author David Pearce, who was at BAS and is now at the University of Northumbria, says,

“What was surprising was the high biomass and diversity we found. This is the first time microbes have been identified living in the sediments of a subglacial Antarctic lake and indicates that life can exist and potentially thrive in environments we would consider too extreme.

“The fact these organisms have survived in such a unique environment could mean they have developed in unique ways which could lead to exciting discoveries for us. This is the early stage and we now need to do more work to further investigate these life forms.”

Some of the life discovered was in the form of fossil DNA showing that many different types of bacteria live there, including a range of extremophiles which are species adapted to the most extreme environments. These use a variety of chemical methods to sustain life both with and without oxygen.

One DNA sequence was related to the most ancient organisms known on Earth and parts of the DNA in twenty three percent has not been previously described. Many of the species are likely to be new to science making clean exploration of the remote lakes isolated under the deeper parts of the ice sheet even more pressing.

Scientists believe organisms living in subglacial lakes could hold clues for how life might survive on other planets.

Late last year a British expedition to drill into Lake Ellsworth was called off after technical difficulties. A US expedition sampled a subglacial environment near the edge of the ice sheet but has yet to report its findings, and a Russian led project has sampled ice near the surface of a subglacial lake and has reported finding signs of life.

Biochemists Resurrect ‘Molecular Fossils’: Findings Challenge Assumptions About Origins of Life

September 16th, 2013

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Before there was life on Earth, there were molecules. A primordial soup. At some point a few specialized molecules began replicating. This self-replication, scientists agree, kick-started a biochemical process that would lead to the first organisms. But exactly how that happened — how those molecules began replicating — has been one of science’s enduring mysteries.

Now, research from UNC School of Medicine biochemist Charles Carter, PhD, appearing in the September 13 issue of the Journal of Biological Chemistry, offers an intriguing new view on how life began. Carter’s work is based on lab experiments during which his team recreated ancient protein enzymes that likely played a vital role in helping create life on Earth. Carter’s finding flies in the face of the widely-held theory that Ribonucleic Acid (RNA) self-replicated without the aid of simple proteins and eventually led to life as we know it.

Artist’s conception of DNA (stock image). (Credit: © Sergey Nivens / Fotolia)

In the early 1980s, researchers found that ribozymes — RNA enzymes — act as catalysts. It was evidence that RNA can be both the blueprints and the chemical catalysts that put those blueprints into action. This finding led to the “RNA World” hypothesis, which posits that RNA alone triggered the rise of life from a sea of molecules.

But for the hypothesis to be correct, ancient RNA catalysts would have had to copy multiple sets of RNA blueprints nearly as accurately as do modern-day enzymes. That’s a hard sell; scientists calculate that it would take much longer than the age of the universe for randomly generated RNA molecules to evolve sufficiently to achieve the modern level of sophistication. Given Earth’s age of 4.5 billion years, living systems run entirely by RNA could not have reproduced and evolved either fast or accurately enough to give rise to the vast biological complexity on Earth today.

“The RNA world hypothesis is extremely unlikely,” said Carter. “It would take forever.”

Moreover, there’s no proof that such ribozymes even existed billions of years ago. To buttress the RNA World hypothesis, scientists use 21st century technology to create ribozymes that serve as catalysts. “But most of those synthetic ribozymes,” Carter said, “bear little resemblance to anything anyone has ever isolated from a living system.”

Carter, who has been an expert in ancient biochemistry for four decades, took a different approach. His experiments are deeply embedded in consensus biology.

Our genetic code is translated by two super-families of modern-day enzymes. Carter’s research team created and superimposed digital three-dimensional versions of the two super-families to see how their structures aligned. Carter found that all the enzymes have virtually identical cores that can be extracted to produce “molecular fossils” he calls Urzymes — Ur meaning earliest or original. The other parts, he said, are variations that were introduced later, as evolution unfolded.

These two Urzymes are as close as scientists have gotten to the actual ancient enzymes that would have populated Earth billions of years ago.

“Once we identified the core part of the enzyme, we cloned it and expressed it,” Carter said. “Then we wanted to see if we could stabilize it and determine if it had any biochemical activity.” They could and it did.

Both Urzymes are very good at accelerating the two reactions necessary to translate the genetic code.

“Our results suggest that there were very active protein enzymes very early in the generation of life, before there were organisms,” Carter said. “And those enzymes were very much like the Urzymes we’ve made.”

The finding also suggests that Urzymes evolved from even simpler ancestors — tiny proteins called peptides. And over time those peptides co-evolved with RNA to give rise to more complex life forms.

In this “Peptide-RNA World” scenario, RNA would have contained the instructions for life while peptides would have accelerated key chemical reactions to carry out those instructions.

“To think that these two Urzymes might have launched protein synthesis before there was life on Earth is totally electrifying,” Carter said. “I can’t imagine a much more exciting result to be working on, if one is interested in the origin of life.”

The study leaves open the question of exactly how those primitive systems managed to replicate themselves — something neither the RNA World hypothesis nor the Peptide-RNA World theory can yet explain. Carter, though, is extending his research to include polymerases — enzymes that actually assemble the RNA molecule. Finding an Urzyme that serves that purpose would help answer that question.

The study’s co-authors include Li Li of UNC and Christopher Francklyn of the University of Vermont, Burlington.

Ancient Ancestor of Tulip Tree Line Identified

September 15th, 2013

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The modern-day tulip tree, state tree of Indiana as well as Kentucky and Tennessee, can trace its lineage back to the time of the dinosaurs, according to newly published research by an Indiana University paleobotanist and a Russian botanist.

The tulip tree, Liriodendron tulipfera, has been considered part of the magnolia family. But David Dilcher of Indiana University Bloomington and Mikhail S. Romanov of the N.V. Tsitsin Main Botanical Garden in Moscow show that it is closely related to fossil plant specimens from the Lower Cretaceous period.

Artist’s reconstruction of Archaeanthus. (Credit: Photo-by David Dilcher)

Their findings suggest the tulip tree line diverged from magnolias more than 100 million years ago and constitutes an independent family, Liriodendraceae, with two living species: one in the Eastern United States and the other in Eastern China. The article, “Fruit structure in Magnoliaceae s.l. and Archaeanthus and their relationships,” appears in the most recent issue of the American Journal of Botany.

The tulip tree, sometimes called tulip poplar or yellow poplar, is one of the largest trees of Eastern North America, sometimes reaching more than 150 feet in height. It is native from southern New England westward to Michigan and south to Louisiana and Florida.

Dilcher, an IU professor emeritus of geological sciences and biology in the College of Arts and Sciences, discovered fossil flowers and fruits resembling those of magnolias and tulip trees in 1975 in Kansas. Dilcher and Peter Crane, now the dean of the School of Forestry and Environmental Studies at Yale University, published information about the fossils and named the plant Archaeanthus.

But the relationship between the fossils and any living plant species remained a mystery until Dilcher met and began working with Romanov, who specializes in study of the magnolia family and its relatives. The researchers used advanced technologies of light, scanning electron and polarizing microscopy to develop a more detailed picture of the Archaeanthus flowers, fruits and seeds and compare them with the flowers, fruits and seeds of contemporary plants.

“We discovered features of the fruits and seeds, not previously detailed, that were more similar to those of the tulip tree line of evolution than to the magnolias,” Dilcher said. “Thus the beautiful tulip tree has a lineage that extends back to the age of the dinosaurs. It has a long, independent history separate from the magnolias and should be recognized as its own flowering plant family.”

While the paper provides new insight into the evolution of the tulip tree line, questions remain, Dilcher said. Scientists don’t know how widespread and various the early members of the tulip tree line may have been, for example. Fossils similar to Archaeanthus have been found in the Southeastern United States. Were there other similar plants, and where did they develop?

Further, the fact that the tulip tree family has survived and evolved for more than 100 million years — albeit in limited and widely divergent ranges — is relevant to understanding how species have developed in the past and how they might fare in the future given changing climate and other factors.

Darwin’s Dilemma Resolved: Evolution’s ‘Big Bang’ Explained by Five Times Faster Rates of Evolution

September 14th, 2013

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A new study led by Adelaide researchers has estimated, for the first time, the rates of evolution during the “Cambrian explosion” when most modern animal groups appeared between 540 and 520 million years ago.

A living arthropod (centipede Cormocephalus) crawls over its 515-million-year-old relative that lived during the Cambrian explosion (trilobite Estaingia). A study of arthropods reveals that morphology and genes evolved five times faster during evolution’s “big bang” compared to all subsequent periods: Fast, but still compatible with Darwin’s theory. Both the centipede and trilobite are found on what is now Kangaroo Island, Australia. (Credit: Michael Lee.)

The findings, published online today in the journal Current Biology, resolve “Darwin’s dilemma”: the sudden appearance of a plethora of modern animal groups in the fossil record during the early Cambrian period.

“The abrupt appearance of dozens of animal groups during this time is arguably the most important evolutionary event after the origin of life,” says lead author Associate Professor Michael Lee of the University of Adelaide’s School of Earth and Environmental Sciences and the South Australian Museum.

“These seemingly impossibly fast rates of evolution implied by this Cambrian explosion have long been exploited by opponents of evolution. Darwin himself famously considered that this was at odds with the normal evolutionary processes.

“However, because of the notorious imperfection of the ancient fossil record, no-one has been able to accurately measure rates of evolution during this critical interval, often called evolution’s Big Bang.

“In this study we’ve estimated that rates of both morphological and genetic evolution during the Cambrian explosion were five times faster than today — quite rapid, but perfectly consistent with Darwin’s theory of evolution.”

The team, including researchers from the Natural History Museum in London, quantified the anatomical and genetic differences between living animals, and established a timeframe over which those differences accumulated with the help of the fossil record and intricate mathematical models. Their modelling showed that moderately accelerated evolution was sufficient to explain the seemingly sudden appearance of many groups of advanced animals in the fossil record during the Cambrian explosion.

The research focused on arthropods (insects, crustaceans, arachnids and their relatives), which are the most diverse animal group in both the Cambrian period and present day.

“It was during this Cambrian period that many of the most familiar traits associated with this group of animals evolved, like a hard exoskeleton, jointed legs, and compound (multi-faceted) eyes that are shared by all arthropods. We even find the first appearance in the fossil record of the antenna that insects, millipedes and lobsters all have, and the earliest biting jaws.” says co-author Dr Greg Edgecombe of the Natural History Museum.

The Final Nail in the Jurassic Park Coffin? Next Generation Sequencing Reveals Absence of DNA in Sub-Fossilized Insects

September 13th, 2013

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It is hardly possible to talk about fossil insects in amber without the 1993 movie Jurassic Park entering the debate. The idea of recreating dinosaurs by extracting DNA from insects in amber has held the fascination of the public for two decades. Claims for successful extraction of DNA from amber up to 130 million-years-old by various scientists in the early 1990s were only seriously questioned when a study at the Natural History Museum, London, was unable to replicate the process. The original claims are now considered by many to be a text-book example of modern contaminant DNA in the samples. Nonetheless, some scientists hold fast to their original claims.

This image shows a sub-fossilized insect in copal. (Credit: Dr. David Penney, University of Manchester)

Research just published in the journal The Public Library of Science ONE (PLOS ONE) by a team of researchers from the Faculty of Life Sciences at The University of Manchester can now confirm that the existence of DNA in amber fossils is highly unlikely. The team led by amber expert Dr David Penney and co-ordinated by ancient DNA expert Professor Terry Brown used highly-sensitive ‘next generation’ sequencing techniques — the most advance type of DNA sequencing — on insects in copal, the sub-fossilized resin precursor of amber.

The research was conducted wearing full forensic suits in the dedicated ancient DNA facility at The University of Manchester, which comprises a suite of independent, physically isolated laboratories, each with an ultra-filtered air supply maintaining positive displacement pressure and a managed access system.

According to Professor Brown: “In the original 1990s studies DNA amplification was achieved by a process called the polymerase chain reaction (PCR), which will preferentially amplify any modern, undamaged DNA molecules that contaminate an extract of partially degraded ancient ones to give false positive results that might be mistaken for genuine ancient DNA. Our approach, using ‘next generation’ sequencing methods is ideal for ancient DNA because it provides sequences for all the DNA molecules in an extract, regardless of their length, and is less likely to give preference to contaminating modern molecules.”

The team concluded that their inability to detect ancient DNA in relatively young (60 years to 10,600 years old) sub-fossilized insects in copal, despite using sensitive next generation methods, suggests that the potential for DNA survival in resin inclusions is no better, and perhaps worse, than that in air-dried museum insects (from which DNA has been retrieved using similar techniques). This raises significant doubts about claims of DNA extraction from fossil insects in amber, many millions of years older than copal.

Dr Penney said: “Intuitively, one might imagine that the complete and rapid engulfment in resin, resulting in almost instantaneous demise, might promote the preservation of DNA in a resin entombed insect, but this appears not to be the case. So, unfortunately, the Jurassic Park scenario must remain in the realms of fiction.”

How Ancient Crocodiles Flourished During the Age of the Dinosaurs?

September 11th, 2013

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New research has revealed the hidden past of crocodiles, showing for the first time how these fierce reptiles evolved and survived in a dinosaur dominated world.

While most modern crocodiles live in freshwater habitats and feed on mammals and fish, their ancient relatives were extremely diverse — with some built for running around like dogs on land and others adapting to life in the open ocean, imitating the feeding behaviour of today’s killer whales.

Research published today [11 September] in the journal Proceedings of the Royal Society B shows, for the first time, how the jaws of ancient crocodiles evolved to enable these animals to survive in vastly different environments, all whilst living alongside the dinosaurs 235 to 65 million years ago.

A sample of jaws from the Mesozoic crocodile fossil record. From top to bottom jaws are from: Kaprosuchus (Cretaceous) (image by Carol Abraczinskas), Simosuchus (Cretaceous), Mariliasuchus (Cretaceous) (courtesy of The American Museum of Natural History), Dakosaurus (Jurassic to Cretaceous) and Cricosaurus (Jurassic to Cretaceous) (courtesy of Jeremías Taborda). (Credit: Image courtesy of University of Bristol)

The study was conducted by Tom Stubbs and Dr Emily Rayfield from the University of Bristol, together with Dr Stephanie Pierce from The Royal Veterinary College and Dr Phil Anderson from Duke University.

Tom Stubbs, who led the research at the University of Bristol, said: “The ancestors of today’s crocodiles have a fascinating history that is relatively unknown compared to their dinosaur counterparts. They were very different creatures to the ones we are familiar with today, much more diverse and, as this research shows, their ability to adapt was quite remarkable.

“Their evolution and anatomical variation during the Mesozoic Era was exceptional. They evolved lifestyles and feeding ecologies unlike anything seen today.”

The research team examined variation in the morphology (shape) and biomechanics (function) of the lower jaws in over 100 ancient crocodiles, using a unique combination of numerical methods.

Dr Stephanie Pierce, from The Royal Veterinary College, said: “We were curious how extinction events and adaptations to extreme environments during the Mesozoic — a period covering over 170 million years — impacted the feeding systems of ancient crocodiles and to do this we focused our efforts on the main food processing bone, the lower jaw.”

By analysing variation in the lower jaw, the researchers provide novel insights into how the feeding systems of ancient crocodiles evolved as the group recovered from the devastating end-Triassic extinction event and subsequently responded to the distribution of ecological resources, such as habitat and foodstuff.

For the first time, the research has shown that, following the end-Triassic extinction, ancient crocodiles invaded the Jurassic seas and evolved jaws built primarily for hydrodynamic efficiency to capture agile prey, such as fish. However, only a small range of elongate lower jaw shapes were suitable in Jurassic marine environments.

The study has also revealed that variation peaked again in the Cretaceous, where ancient crocodiles evolved a great variety of lower jaw shapes, as they adapted to a diverse range of feeding ecologies and terrestrial environments, alongside the dinosaurs.

Surprisingly, the lower jaws of Cretaceous crocodiles did not have a great amount of biomechanical variation and, instead, the fossil record points towards novel adaptations in other areas of their anatomy, such as armadillo-like body armour.

Dr Pierce added: “Our results show that the ability to exploit a variety of different food resources and habitats, by evolving many different jaw shapes, was crucial to recovering from the end-Triassic extinction and most likely contributed to the success of Mesozoic crocodiles living in the shadow of the dinosaurs.”

This exceptional variation has never before been explored numerically, with no studies ever having incorporated such a wide range of crocodiles over such a long time period.

Beneath Earth’s Surface, Scientists Find Long ‘Fingers’ of Heat

September 9th, 2013

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Scientists seeking to understand the forces at work beneath the surface of Earth have used seismic waves to detect previously unknown “fingers” of heat, some of them thousands of miles long, in Earth’s upper mantle. Their discovery, published Sept. 5 in Science Express, helps explain the “hotspot volcanoes” that give birth to island chains such as Hawai’i and Tahiti.

Many volcanoes arise at collision zones between the tectonic plates, but hotspot volcanoes form in the middle of the plates. Geologists have hypothesized that upwellings of hot, buoyant rock rise as plumes from deep within Earth’s mantle — the layer between the crust and the core that makes up most of Earth’s volume — and supply the heat that feeds these mid-plate volcanoes.

But some hotspot volcano chains are not easily explained by this simple model, a fact which suggests there are more complex interactions between these hot plumes and the upper mantle. Now, a computer modeling approach, developed by University of Maryland seismologist Vedran Lekic and colleagues at the University of California Berkeley, has produced new seismic wave imagery which reveals that the rising plumes are, in fact, influenced by a pattern of finger-like structures carrying heat deep beneath Earth’s oceanic plates.

Seismic waves are waves of energy produced by earthquakes, explosions and volcanic eruptions, which can travel long distances below Earth’s surface. As they travel through layers of different density and elasticity, their shape changes. A global network of seismographs records these changing waveforms. By comparing the waveforms from hundreds of earthquakes recorded at locations around the world, scientists can make inferences about the structures through which the seismic waves have traveled.

The process, known as seismic tomography, works in much the same way that CT scans (computed tomography) reveal structures hidden beneath the surface of the human body. But since we know much less about the structures below Earth’s surface, seismic tomography isn’t easy to interpret. “The Earth’s crust varies a lot, and being able to represent that variation is difficult, much less the structure deeper below” said Lekic, an assistant professor of geology at the College Park campus.

Slow-moving seismic waves, hotter than surrounding material, interact with plumes rising from the mantle to affect the formation of hotspot volcanic islands. (Credit: Illustration: Scott French)

Until recently, analyses like the one in the study would have taken up to 19 years of computer time. While studying for his doctorate with the study’s senior author, UC Berkeley Prof. Barbara Romanowicz, Lekic developed a method to more accurately model waveform data while still keeping computer time manageable, which resulted in higher-resolution images of the interaction between the layers of Earth’s mantle.

By refining this method, a research team led by UC Berkeley graduate student Scott French found finger-like channels of low-speed seismic waves flowing about 120 to 220 miles below the sea floor, and stretching out in bands about 700 miles wide and 1,400 miles apart. The researchers also discovered a subtle but important difference in speed: at this depth, seismic waves typically travel about 2.5 to 3 miles per second, but the average seismic velocity in the channels was 4 percent slower. Because higher temperatures slow down seismic waves, the researchers infer that the channels are hotter than the surrounding material.

“We estimate that the slowdown we’re seeing could represent a temperature increase of up to 200 degrees Celsius,” or about 390 degrees Fahrenheit, said French, the study’s study lead author. At these depths, absolute temperatures in the mantle are about 1,300 degrees Celsius, or 2,400 degrees Fahrenheit, the researchers said.

Geophysicists have long theorized that channels akin to those revealed in the computer model exist, and are interacting with the plumes in Earth’s mantle that feed hotspot volcanoes. But the new images reveal for the first time the extent, depth and shape of these channels. And they also show that the fingers align with the motion of the overlying tectonic plate. The researchers hypothesize that these channels may be interacting in complex ways with both the tectonic plates above them and the hot plumes rising from below.

“This global pattern of finger-like structures that we’re seeing, which has not been documented before, appears to reflect interactions between the upwelling plumes and the motion of the overlying plates,” Lekic said. “The deflection of the plumes into these finger-like channels represents an intermediate scale of convection in the mantle, between the large-scale circulation that drives plate motions and the smaller scale plumes, which we are now starting to image.”

“The exact nature of those interactions will need further study,” said French, “but we now have a clearer picture that can help us understand the ‘plumbing’ of Earth’s mantle responsible for hotspot volcano islands like Tahiti, Reunion and Samoa.”

Rare Fossil Ape Cranium Discovered in China

September 8th, 2013

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A team of researchers has discovered the cranium of a fossil ape from Shuitangba, a Miocene site in Yunnan Province, China. The juvenile cranium of the fossil ape Lufengpithecus is significant, according to team member Nina Jablonski, Distinguished Professor of Anthropology at Penn State.

The cranium of the fossil juvenile ape found at a Miocene site in Yunnan Province, China. (Credit: Xue-Ping Ji, Yunnan Institute of Cultural Relics and Archaeology)

Jablonski noted that juvenile crania of apes and hominins are extremely rare in the fossil record, especially those of infants and young juveniles. This cranium is only the second relatively complete cranium of a young juvenile in the entire Miocene — 23-25 million years ago — record of fossil apes throughout the Old World, and both were discovered from the late Miocene of Yunnan Province.
The cranium is also noteworthy for its age. Shuitangba, the site from which it was recovered, at just over 6 million years old, dates to near the end of the Miocene, a time when apes had become extinct in most of Eurasia. Shuitangba has also produced remains of the fossil monkey, Mesopithecus, which represents the earliest occurrence of monkeys in East Asia.

Jablonski was co-author of a recent paper online in the Chinese Science Bulletin that described the discovery.

“The preservation of the new cranium is excellent, with only minimal post-depositional distortion,” Jablonski said. “This is important because all previously discovered adult crania of the species to which it is assigned, Lufengpithecus lufengensis, were badly crushed and distorted during the fossilization process. In living ape species, cranial anatomy in individuals at the same stage of development as the new fossil cranium already show a close resemblance to those of adults.”

Therefore, the new cranium, despite being from a juvenile, gives researchers the best look at the cranial anatomy of Lufengpithecus lufengensis.

“Partly because of where and when Lufengpithecus lived, it is considered by most to be in the lineage of the extant orangutan, now confined to Southeast Asia but known from the late Pleistocene of southern China as well,” Jablonski said.

However, the researchers noted the cranium shows little resemblance to those of living orangutans, and in particular, shows none of what are considered to be key diagnostic features of orangutan crania. Lufengpithecus therefore appears to represent a late surviving lineage of Eurasian apes, but with no certain affinities yet clear.

The survival of this lineage is not entirely surprising since southern China was less affected by climatic deterioration during the later Miocene that resulted in the extinction of many ape species throughout the rest of Eurasia. The researchers are hopeful that further excavations will produce the remains of adult individuals, which will allow them to better assess the relationships among members of this lineage as well as the relationships of this lineage to other fossil and extant apes.