Conotubus fossils provide new clues about fossil formation

A new study from University of Missouri and Virginia Tech researchers is challenging accepted ideas about how ancient soft-bodied organisms become part of the fossil record. Findings suggest that bacteria involved in the decay of those organisms play an active role in how fossils are formed — often in a matter of just a few tens to hundreds of years. Understanding the relationship between decay and fossilization will inform future study and help researchers interpret fossils in a new way.

“The vast majority of the fossil record is composed of bones and shells,” said James Schiffbauer, assistant professor of geological sciences in the College of Arts and Science at MU. “Fossils of soft-bodied animals like worms and jellyfish, however, provide our only views onto the early evolution of animal life. Most hypotheses as to the preservation of these soft tissues focus on passive processes, where normal decay is halted or impeded in some way, such as by sealing off the sediments where the animal is buried. Our team is instead detailing a scenario where the actual decay helped ‘feed’ the process turning the organisms into fossils — in this case, the decay of the organisms played an active role in creating fossils.”

Conotubus. Three-dimensionally pyritized tube-worm like fossils, Conotubus, from the 550 million year old Gaojiashan Lagerstätte, Shaanxi Province, South China. Credit: Yaoping Cai, Northwest University, Xi'an, China.

Conotubus. Three-dimensionally pyritized tube-worm like fossils, Conotubus, from the 550 million year old Gaojiashan Lagerstätte, Shaanxi Province, South China.
Credit: Yaoping Cai, Northwest University, Xi’an, China.

Schiffbauer studied a type of fossil animal from the Ediacaran Period called Conotubus, which lived more than 540 million years ago. He noted that these fossils are either replicated by, or associated with, pyrite — commonly called fool’s gold. The tiny fossils are tube-shaped and believed to have been composed of substances similar at least in hardness to human fingernails. These fossilized tubes are all that remain of the soft-bodied animals that inhabited them and most likely resembled worms or sea anemone-like animals.

“Most of the animals that had once lived on the Earth — with estimates eclipsing 10 billion species — were never preserved in the fossil record, but in our study we have a spectacular view of a tinier fraction of soft-bodied animals,” said Shuhai Xiao, professor of geobiology at Virginia Tech and a co-author on this study. “We asked the important questions of how, and under what special conditions, these soft-tissued organisms can escape the fate of complete degradation and be preserved in the rock record.”

Schiffbauer and his team performed a sophisticated suite of chemical analyses of these fossils to determine what caused the pyrite to form. They found that the fool’s gold on the organisms’ outer tube formed when bacteria first began consuming the animal’s soft tissues, with the decay actually promoting the formation of pyrite.

“Normally, the Earth is good at cleaning up after itself,” Schiffbauer said. “In this case, the bacteria that helped break down these organisms also are responsible for preserving them as fossils. As the decay occurred, pyrite began replacing and filling in space within the animal’s exoskeleton, preserving them. Additionally, we found that this process happened in the space of a few years, perhaps even as low as 12 to 800. Ultimately, these new findings will help scientists to gain a better grasp of why these fossils are preserved, and what features represent the fossilization process versus original biology, so we can better reconstruct the evolutionary tree of life.

Shortening tails gave early birds a leg up

A radical shortening of their bony tails over 100 million years ago enabled the earliest birds to develop versatile legs that gave them an evolutionary edge, a new study shows.

A team led by Oxford University scientists examined fossils of the earliest birds from the Cretaceous Period, 145-66 million years ago, when early birds, such as Confuciusornis, Eoenantiornis, and Hongshanornis, lived alongside their dinosaur kin. At this point birds had already evolved powered flight, necessitating changes to their forelimbs, and the team investigated how this new lifestyle related to changes in their hind limbs (legs).

The team made detailed measurements of early bird fossils from all over the world including China, North America, and South America. An analysis of this data showed that the loss of their long bony tails, which occurred after flight had evolved, led to an explosion of diversity in the hind limbs of early birds, prefiguring the amazing variety of talons, stilts, and other specialised hind limbs that have helped to make modern birds so successful.

A report of the research is published this week in Proceedings of the Royal Society B.

This image shows fossil birds from the time of dinosaurs [left image: Eoenatiornis, right image: Hongshanornis] showing they had diverse types of legs. Credit: Roger Close

This image shows fossil birds from the time of dinosaurs [left image: Eoenatiornis, right image: Hongshanornis] showing they had diverse types of legs.
Credit: Roger Close

‘These early birds were not as sophisticated as the birds we know today — if modern birds have evolved to be like stealth bombers then these were more like biplanes,’ said Dr Roger Benson of Oxford University’s Department of Earth Sciences, who led the research. ‘Yet what surprised us was that despite some still having primitive traits, such as teeth, these early birds display an incredibly diverse array of versatile legs.’By comparing measurements of the main parts of the legs of early birds — upper leg, shin, and foot — to those of their dinosaur relatives Dr Benson and co-author Dr Jonah Choiniere of the University of the Witwatersrand, South Africa, were able to determine whether bird leg evolution was exceptional compared to leg evolution in dinosaurs.

‘Our work shows that, whilst they may have started off as just another type of dinosaur, birds quickly made a rather special evolutionary breakthrough that gave them abilities and advantages that their dinosaur cousins didn’t have,’ said Dr Rogers. ‘Key to this special ‘birdness’ was losing the long bony dinosaur tail — as soon as this happened it freed up their legs to evolve to become highly versatile and adaptable tools that opened up new ecological niches.’

It was developing these highly versatile legs, rather than powered flight, that saw the evolutionary diversification of early birds proceed faster than was generally true of other dinosaurs.

Bridgmanite:Earth’s most abundant mineral

An ancient meteorite and high-energy X-rays have helped scientists conclude a half century of effort to find, identify and characterize a mineral that makes up 38 percent of the Earth.

And in doing so, a team of scientists led by Oliver Tschauner, a mineralogist at the University of Las Vegas, clarified the definition of the Earth’s most abundant mineral — a high-density form of magnesium iron silicate, now called Bridgmanite — and defined estimated constraint ranges for its formation. Their research was performed at the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility located at DOE’s Argonne National Laboratory.

A section of meteorite that landed in Australia in 1879. Bridgmanite was formed and trapped in the dark veins from the intense, quick shock of asteroid collisions. A team of scientists clarified the definition of Bridgmanite, a high-density form of magnesium iron silicate and the Earth's most abundant mineral – using Argonne National Laboratory's Advanced Photon Source. Credit: Tschauneret et al, Science

A section of meteorite that landed in Australia in 1879. Bridgmanite was formed and trapped in the dark veins from the intense, quick shock of asteroid collisions. A team of scientists clarified the definition of Bridgmanite, a high-density form of magnesium iron silicate and the Earth’s most abundant mineral – using Argonne National Laboratory’s Advanced Photon Source.
Credit: Tschauneret et al, Science

The mineral was named after 1964 Nobel laureate and pioneer of high-pressure research Percy Bridgman. The naming does more than fix a vexing gap in scientific lingo; it also will aid our understanding of the deep Earth.

To determine the makeup of the inner layers of the Earth, scientists need to test materials under extreme pressure and temperatures. For decades, scientists have believed a dense perovskite structure makes up 38 percent of the Earth’s volume, and that the chemical and physical properties of Bridgmanite have a large influence on how elements and heat flow through the Earth’s mantle. But since the mineral failed to survive the trip to the surface, no one has been able to test and prove its existence — a requirement for getting a name by the International Mineralogical Association.

Shock-compression that occurs in collisions of asteroid bodies in the solar system create the same hostile conditions of the deep Earth — roughly 2,100 degrees Celsius (3,800 degrees Farenheit) and pressures of about 240,000 times greater than sea-level air pressure. The shock occurs fast enough to inhibit the Bridgmanite breakdown that takes place when it comes under lower pressure, such as the Earth’s surface. Part of the debris from these collisions falls on Earth as meteorites, with the Bridgmanite “frozen” within a shock-melt vein. Previous tests on meteorites using transmission electron microscopy caused radiation damage to the samples and incomplete results.

So the team decided to try a new tactic: non-destructive micro-focused X-rays for diffraction analysis and novel fast-readout area-detector techniques. Tschauner and his colleagues from Caltech and the GeoSoilEnviroCARS, a University of Chicago-operated X-ray beamline at the APS at Argonne National Laboratory, took advantage of the X-rays’ high energy, which gives them the ability to penetrate the meteorite, and their intense brilliance, which leaves little of the radiation behind to cause damage.

The team examined a section of the highly shocked L-chondrite meteorite Tenham, which crashed in Australia in 1879. The GSECARS beamline was optimal for the study because it is one of the nation’s leading locations for conducting high-pressure research.

Bridgmanite grains are rare in the Tenhma meteorite, and they are smaller than 1 micrometer in diameter. Thus the team had to use a strongly focused beam and conduct highly spatially resolved diffraction mapping until an aggregate of Bridgmanite was identified and characterized by structural and compositional analysis.

This first natural specimen of Bridgmanite came with some surprises: It contains an unexpectedly high amount of ferric iron, beyond that of synthetic samples. Natural Bridgmanite also contains much more sodium than most synthetic samples. Thus the crystal chemistry of natural Bridgmanite provides novel crystal chemical insights. This natural sample of Bridgmanite may serve as a complement to experimental studies of deep mantle rocks in the future.

Prior to this study, knowledge about Bridgmanite’s properties has only been based on synthetic samples because it only remains stable below 660 kilometers (410 miles) depth at pressures of above 230 kbar (23 GPa). When it is brought out of the inner Earth, the lower pressures transform it back into less dense minerals. Some scientists believe that some inclusions on diamonds are the marks left by Bridgmanite that changed as the diamonds were unearthed.

The team’s results were published in the November 28 issue of the journal Science as “Discovery of bridgmanite, the most abundant mineral in Earth, in a shocked meteorite,” by O. Tschauner at University of Nevada in Las Vegas, N.V.; C. Ma; J.R. Beckett; G.R. Rossman at California Institute of Technology in Pasadena, Calif.; C. Prescher; V.B. Prakapenka at University of Chicago in Chicago, IL.

This research was funded by the U.S. Department of Energy, NASA, and NSF.

Aquilops : Oldest horned dinosaur species in North America

cientists have named the first definite horned dinosaur species from the Early Cretaceous in North America, according to a study published December 10, 2014 in the open-access journal PLOS ONE by Andrew Farke from Raymond M. Alf Museum of Paleontology and colleagues.

This is a an artist's reconstruction of Aquilops in its environment in ancient Montana

This is a an artist’s reconstruction of Aquilops in its environment in ancient Montana
Credit: Copyright Brian Engh, courtesy of Raymond M. Alf Museum of Paleontology; CC-BY

The limited fossil record for neoceratopsian–or horned dinosaurs–from the Early Cretaceous in North America restricts scientists’ ability to reconstruct the early evolution of this group. The authors of this study have discovered a dinosaur skull in Montana that represents the first horned dinosaur from the North American Early Cretaceous that they can identify to the species level. The authors named the dinosaur Aquilops americanus, which exhibits definitive neoceratopsian features and is closely related to similar species in Asia. The skull is comparatively small, measuring 84 mm long, and is distinguished by several features, including a strongly hooked rostral bone, or beak-like structure, and an elongated and sharply pointed cavity over the cheek region. When alive, the authors estimate it was about the size of a crow.

This discovery, combined with neoceratopsian fossil records from elsewhere, allows the authors to support a late Early Cretaceous (~113-105 million years ago) intercontinental migratory event between Asia and North America, as well as support for a complex set of migratory events for organisms between North America and Asia later in the Cretaceous. However, to better reconstruct the timing and mode of these events, additional fieldwork will be necessary.

“Aquilops lived nearly 20 million years before the next oldest horned dinosaur named from North America,” said Andrew Farke. “Even so, we were surprised that it was more closely related to Asian animals than those from North America.”

volcanoes may be much closer than thought

Credit: Virginia Tech
 

Traditional thought holds that hot updrafts from the Earth’s core cause volcanoes, but researchers say eruptions may stem from the asthenosphere, a layer closer to the surface.

Credit: Virginia Tech

A long-held assumption about the Earth is discussed in today’s edition of Science, as Don L. Anderson, an emeritus professor with the Seismological Laboratory of the California Institute of Technology, and Scott King, a professor of geophysics in the College of Science at Virginia Tech, look at how a layer beneath the Earth’s crust may be responsible for volcanic eruptions.

The discovery challenges conventional thought that volcanoes are caused when plates that make up the planet’s crust shift and release heat.

Instead of coming from deep within the interior of the planet, the responsibility is closer to the surface, about 80 kilometers to 200 kilometers deep — a layer above the Earth’s mantle, known as the as the asthenosphere.

“For nearly 40 years there has been a debate over a theory that volcanic island chains, such as Hawaii, have been formed by the interaction between plates at the surface and plumes of hot material that rise from the core-mantle boundary nearly 1,800 miles below the Earth’s surface,” King said. “Our paper shows that a hot layer beneath the plates may explain the origin of mid-plate volcanoes without resorting to deep conduits from halfway to the center of the Earth.”

Traditionally, the asthenosphere has been viewed as a passive structure that separates the moving tectonic plates from the mantle.

As tectonic plates move several inches every year, the boundaries between the plates spawn most of the planet’s volcanoes and earthquakes.

“As the Earth cools, the tectonic plates sink and displace warmer material deep within the interior of the Earth,” explained King. “This material rises as two broad, passive updrafts that seismologists have long recognized in their imaging of the interior of the Earth.”

The work of Anderson and King, however, shows that the hot, weak region beneath the plates acts as a lubricating layer, preventing the plates from dragging the material below along with them as they move.

The researchers show this lubricating layer is also the hottest part of the mantle, so there is no need for heat to be carried up to explain mid-plate volcanoes.

“We’re taking the position that plate tectonics and mid-plate volcanoes are the natural results of processes in the plates and the layer beneath them,” King said.

Fossil hunters find skeleton of 40,000-year-old woolly mammoth in North Sea

Fossil hunters searching for ancient relics have found the skeleton of a 40,000-year-old woolly mammoth in North Sea. The team of archaeologists, salvagers and palaeontologists trawled the waters off the east coast of Britain at a depth of 100 feet. North Sea Fossils, who are based in Urk, Netherlands, include an expert they call “Mr Mammoth” and are in search of the remains of extinct animals in the dark depths. Bones of animals including woolly rhinos, Irish elks and parts of the male skeleton of an 11-foot tall woolly mammoth, including its skull and tusks, have all been brought up and collected. A prehistoric skull of a European bison, also known as a Wisent, was also discovered lying on the North Sea bed.

Carbon dating tests revealed the bones belonged to a mammoth that roamed the planet around 40,000 years ago.Markus Broch, who works at North Sea Fossils, said it is “extremely rare” to find and later assemble a complete mammoth skeleton.Mr Broch said: “During the Ice Age there was no sea between Holland and England and these great beasts roamed and died there.”That is why their bones are still found by boats fishing in the North Sea.

“My father-in-law, who is a fisherman, started collecting these bones at young age because he was fascinated by them, and has now assembled a very large collection “We started selling duplicates from his collection online some years ago, which went so well that our business have grown and grown.

“Most weeks we go to the fishing ports to meet the fishing vessels and buy the fossils they caught.”Sometimes we charter a boat of our own and go for special ‘fossil hunting’ expeditions.”Because we see so many fossils we work very closely with the leading experts in the field, such as Dick Mol, who is the world’s leading authority on mammoths.”We have assembled a number of complete skeletons of mammoths, something very few companies in the world can do.”

The skull of an adult male mammoth being fished up on the North Sea just off the coast of Rotterdam by Dutch fishermen

The skull of an adult male mammoth being fished up on the North Sea just off the coast of Rotterdam by Dutch fishermen

The salvagers have managed to piece together the entire mammoth skeleton after initially discovering the skull and tusks of the animal in 2012.

The firm travelled out to sea and recovered a stash of other mammoth fossils using deep sea trawler nets before piecing them together at their base in Urk.Other items found by the firm include parts of sabre-toothed tigers, the skull of a woolly rhino and the cranium of a reindeer.Mammoths were first described in 1799 by Johann Friedrich Blumenback, a German scientist.He gave the name Elephas primigenius to elephant-like bones found in Europe.

The bones belonged to the woolly mammoth which was later considered to be a distinct genus and renamed Mamuthus primigenus.The species found by North Sea Fossils were known to roam through parts of Central Europe around 40,000 years ago.

Source: An article in Telegraph

 

Turtles and dinosaurs: evolution of turtles

A team of scientists, including researchers from the California Academy of Sciences, has reconstructed a detailed “tree of life” for turtles. The specifics of how turtles are related — to one another, to other reptiles, and even to dinosaurs — have been hotly debated for decades. Next generation sequencing technologies in Academy labs have generated unprecedented amounts of genetic information for a thrilling new look at turtles’ evolutionary history. These high-tech lab methods revolutionize the way scientists explore species origins and evolutionary relationships, and provide a strong foundation for future looks into Earth’s fossil record.

Research results, appearing in Molecular Phylogenetics and Evolution, describe how a new genetic sequencing technique called Ultra Conserved Elements (UCE) reveal turtles’ closest relatives across the animal kingdom. The new genetic tree uses an enormous amount of data to refute the notion that turtles are most closely related to lizards and snakes. Instead, authors place turtles in the newly named group “Archelosauria” with their closest relatives: birds, crocodiles, and dinosaurs. Scientists suspect the new group will be the largest group of vertebrates to ever receive a new scientific name.

The UCE technique used in high-tech labs allowed scientists to move beyond years of speculation and place the Archelosauria group in its rightful place on the reptile tree of life. UCE has been available since 2012, yet scientists are just beginning to tap its potential for generating enormous amounts of genetic data across vertebrates.

“Calling this is an exciting new era of sequencing technology is an understatement,” says Brian Simison, PhD, Director of the Academy’s Center for Comparative Genomics (CCG) that analyzed the study’s massive amount of data. The CCG is a state-of-the-art facility composed of a sequencing lab, frozen DNA collection, and computing resources that serves as the Academy’s core genetic center. Established in the summer of 2008, the CCG continues to refine Academy research — including new turtle findings — on a global, evolutionary scale.

“In the space of just five years, reasonably affordable studies using DNA sequencing have advanced from using only a handful of genetic markers to more than 2,000 — an unbelievable amount of DNA,” adds Simison. “New techniques like UCE dramatically improve our ability to help resolve decades-long evolutionary mysteries, giving us a clear picture of how animals like turtles evolved on our constantly-changing planet.”

Major findings also resolve an evolutionary mystery surrounding softshell turtles — a bizarre group of scale-less turtles with snorkel-like snouts. Until now, studies linked softshell turtles with a smaller semi-aquatic group called mud turtles, despite the fact that softshells appear in the fossil record long before their mud-loving counterparts. The Academy’s study places softshells in a league of their own on the evolutionary tree, quite far removed from any turtle relatives. Their long independent history helps explain their striking looks as well as their ancient presence in the fossil record.

Study coauthor James Parham, PhD — Academy Research Associate, Assistant Professor of Geological Sciences at Cal State Fullerton, and turtle expert — says cutting-edge testing techniques bring a new level of clarity to more than two decades of his turtle research. With large amounts of data backing up each evolutionary branch on the turtle tree of life, scientists are able to compare their evolution not only across species, but also across each continent’s corresponding fossil records.

“I have been working on the evolutionary relationships of turtles for over 20 years using a variety of methods,” says Parham. “Fossils are essential for showing us what extinct turtles looked like, but also in letting us know when and where they lived in the past.”

Parham notes that studying turtle fossils — particularly the physical features of their bones — hasn’t always painted an accurate evolutionary picture of turtle relationships across continents and through time. “The turtle tree of life based on fossil turtle anatomy didn’t match up with the timing of their appearance in the fossil record, as well as their geography,” Parham says. “But the tree of life generated at the Academy’s CCG is consistent with time and space patterns we’ve gathered from the fossil record. These new testing techniques help reconcile the information from DNA and fossils, making us confident that we’ve found the right tree.”

Lava erupting on sea floor linked to deep-carbon cycle

Scientists from the Smithsonian and the University of Rhode Island have found unsuspected linkages between the oxidation state of iron in volcanic rocks and variations in the chemistry of the deep Earth. Not only do the trends run counter to predictions from recent decades of study, they belie a role for carbon circulating in the deep Earth.The team’s research was published May 2 in Science Express.

Elizabeth Cottrell, lead author and research geologist at the Smithsonian’s National Museum of Natural History, and Katherine Kelley at the University of Rhode Island’s Graduate School of Oceanography measured the oxidation state of iron, which is the amount of iron that has a 3+ versus a 2+ electronic charge, in bits of magma that froze to a glass when they hit the freezing waters and crushing pressures of the sea floor. Due to the high precision afforded by the spectroscopic technique they used, the researchers found very subtle variations in the iron-oxidation state that had been overlooked by previous investigations.

Molten magma erupted onto the seafloor freezes to glass that contains clues to its origin in Earth's deep interior and ancient past (field of view ~1 cm). Volcanic glasses like this one may reveal a link between Earth's oxidation state and the deep carbon cycle. Credit: Glenn Macpherson and Tim Gooding

Molten magma erupted onto the seafloor freezes to glass that contains clues to its origin in Earth’s deep interior and ancient past (field of view ~1 cm). Volcanic glasses like this one may reveal a link between Earth’s oxidation state and the deep carbon cycle.
Credit: Glenn Macpherson and Tim Gooding

The variations correlate with what Cottrell described as the “fingerprints” of the deep Earth rocks that melted to produce the lavas — but not in the way previous researchers had predicted. The erupted lavas that have lower concentrations of 3+ iron also have higher concentrations of elements such as barium, thorium, rubidium and lanthanum, that concentrate in the lavas, rather than staying in their deep Earth home. More importantly, the oxidation state of iron also correlates with elements that became enriched in lavas long ago, and now, after billions of years, show elevated ratios of radiogenic isotopes. Because radiogenic isotopic ratios cannot be modified during rock melting and eruption, Cottrell called this “a dead ringer for the source of the melt itself.”

Carbon is one of the “geochemical goodies” that tends to become enriched in the lava when rocks melt. “Despite is importance to life on this planet, carbon is a really tricky element to get a handle on in melts from the deep Earth,” said Cottrell. “That is because carbon also volatilizes and is lost to the ocean waters such that it can’t easily be quantified in the lavas themselves. As humans we are very focused on what we see up here on the surface. Most people probably don’t recognize that the vast majority of carbon — the backbone of all life — is located in the deep Earth, below the surface — maybe even 90 percent of it.”

The rocks that the team analyzed that were reduced also showed a greater influence of having melted in the presence of carbon than those that were oxidized. “And this makes sense because for every atom of carbon present at depth it has to steal oxygen away from iron as it ascends toward the surface,” said Cottrell. This is because carbon is not associated with oxygen at depth, it exists on its own, like in the mineral diamond. But by the time carbon erupts in lava, it is surrounded by oxygen. In this way, concludes Cottrell, “carbon provides both a mechanism to reduce the iron and also a reasonable explanation for why these reduced lavas are enriched in ways we might expect from melting a carbon-bearing rock.”

Tricky take-off kept pterodactyls grounded

A new study, which teamed cutting-edge engineering techniques with paleontology, has found that take-off capacity may have determined body size limits in extinct flying reptiles. The research simulated pterodactyl flight using computer modeling, and will be presented at the upcoming Society of Vertebrate Paleontology meeting in Berlin. Findings suggest that a pterodactyl with a wingspan of 12m or more would simply not be able to get off the ground.

Pterosaurs (commonly known as pterodactyls) were truly giants of the sky. With wingspans of up to 10m, the largest species may have weighed as much as a quarter of a ton. They would have dwarfed the largest known bird at just one third this size. How could such behemoths stay aloft? What prevented them from becoming even bigger?

These questions sparked a novel partnership between Colin Palmer: entrepreneur, mechanical engineer and now doctoral student at Bristol University (UK); and Mike Habib: anatomist and paleontologist at University of Southern California.

“It has been fascinating to apply an engineering approach to understanding biological systems” says Palmer, who has worked on yachts, hovercraft, sailing vessels and windmills before turning to pterosaurs. “Working with Colin has been particularly rewarding” says paleontologist Habib “as we have complimentary skill sets and come at the problem from different backgrounds.”

 

Pterosaur hunting is illustrated. - Illustration by Mark Witton

Pterosaur hunting is illustrated. – Illustration by Mark Witton

The pair used 3D imaging of fossils to create a computer model of a pterosaur with a 6m wingspan. This model was then scaled up to create enlarged models with 9m and 12m wingspans. They were used to estimate the wing strength, flexibility, flying speed and power required for flight in massive pterosaurs.

Results showed that even the largest pterosaur model could sustain flight by using intermittent powered flight to find air currents for gliding. It could also slow down sufficiently to make a safe landing because the pterosaurs wing is formed from a flexible membrane.

Take-off, on the other hand, proved an entirely greater challenge. Unlike modern birds, pterosaur anatomy suggests that they used both their arms and legs to push themselves off the ground during take-off, a maneuver known as the ‘quadrupedal launch’. However, once wingspans approached 12m, the push-off force required to get the model off the ground was too great.

The challenge of propelling a 400kg animal using a quadrupedal launch kept the 12m-wingspan model strictly on terra firma. Palmer concludes “Getting into the air ultimately limited pterosaur size. Even with their unique four legged launch technique, the iron laws of physics eventually caught up with these all time giants of the cretaceous skies.”

Note: This story has been adapted from a news release issued by the Society of Vertebrate Paleontology

Erosion may trigger earthquakes

Researchers from laboratories at Géosciences Rennes (CNRS/Université de Rennes 1)*, Géosciences Montpellier (CNRS/Université de Montpellier 2) and Institut de Physique du Globe de Paris (CNRS/IPGP/Université Paris Diderot), in collaboration with a scientist in Taiwan, have shown that surface processes, i.e. erosion and sedimentation, may trigger shallow earthquakes (less than five kilometers deep) and favor the rupture of large deep earthquakes up to the surface. Although plate tectonics was generally thought to be the only persistent mechanism able to influence fault activity, it appears that surface processes also increase stresses on active faults, such as those in Taiwan, one of the world’s most seismic regions.

The work is published in Nature Communications on 21 November 2014.

Over the last few decades, many studies have focused on the evolution of mountain range landscapes over geological time (1 to 100 million years). The aim is to better understand the dynamics and interactions between erosion, sedimentation and tectonic deformation processes. Recent work has shown that Earth’s surface can undergo major changes in just a few days, months or years, for instance during extreme events such as typhoons or high magnitude earthquakes. Such events cause many landslides and an increase in sedimentary transport into rivers, as was the case in 2009 when typhoon Morakot struck Taiwan, leading to abrupt erosion of landscapes. Such rapid changes to the shape of Earth’s surface alter the balance of forces at the site of deep active faults.

In Taiwan, where erosion and deformation rates are among the highest in the world, the researchers showed that erosion rates of the order of 0.1 to 20 millimeters per year can cause an increase of the order of 0.1 to 10 bar in stresses on faults located nearby. Such forces are probably enough to trigger shallow earthquakes (less than five kilometers deep) or to favor the rupture of deep earthquakes up to the surface, especially if they are amplified by extreme erosion events caused by typhoons and high magnitude earthquakes. The researchers have thus shown that plate tectonics is not the only persistent mechanism able to influence the activity of seismic faults, and that surface processes such as erosion and sedimentation can increase stresses on active faults sufficiently to cause shallow earthquakes.

Thanks to an analysis of the relationships between surface processes and active deformation of Earth in near real-time, this study provides new perspectives for understanding the mechanisms that trigger earthquakes.

*The Géosciences Rennes laboratory is part of the Observatoire des Sciences de l’Univers de Rennes.

Citation: CNRS. “Erosion may trigger earthquakes.” ScienceDaily. ScienceDaily, 21 November 2014. <www.sciencedaily.com/releases/2014/11/141121082911.htm>