What did the first snakes look like?

The original snake ancestor was a nocturnal, stealth-hunting predator that had tiny hindlimbs with ankles and toes, according to research published in the open access journal BMC Evolutionary Biology.

The study, led by Yale University, USA, analyzed fossils, genes, and anatomy from 73 snake and lizard species, and suggests that snakes first evolved on land, not in the sea, which contributes to a longstanding debate. They most likely originated in the warm, forested ecosystems of the Southern Hemisphere around 128 million years ago.

This is a reconstruction of the ancestral crown-group snake, based on this study. Artwork by Julius Csotonyi. Credit: Julius Csotonyi

This is a reconstruction of the ancestral crown-group snake, based on this study. Artwork by Julius Csotonyi.
Credit: Julius Csotonyi

Snakes show incredible diversity, with over 3,400 living species found in a wide range of habitats, such as land, water and in trees. But little is known about where and when they evolved, and how their original ancestor looked and behaved.

Lead author Allison Hsiang said: “While snake origins have been debated for a long time, this is the first time these hypotheses have been tested thoroughly using cutting-edge methods. By analyzing the genes, fossils and anatomy of 73 different snake and lizard species, both living and extinct, we’ve managed to generate the first comprehensive reconstruction of what the ancestral snake was like.”

By identifying similarities and differences between species, the team constructed a large family tree and illustrated the major characteristics that have played out throughout snake evolutionary history.

Their results suggest that snakes originated on land, rather than in water, during the middle Early Cretaceous period (around 128.5 million years ago), and most likely came from the ancient supercontinent of Laurasia. This period coincides with the rapid appearance of many species of mammals and birds on Earth.

The ancestral snake likely possessed a pair of tiny hindlimbs, and targeted soft-bodied vertebrate and invertebrate prey that were relatively large in size compared to prey targeted by lizards at the time. While the snake was not limited to eating very small animals, it had not yet developed the ability to manipulate prey much larger than itself by using constriction as a form of attack, as seen in modern Boa constrictors.

While many ancestral reptiles were most active during the daytime (diurnal), the ancestral snake is thought to have been nocturnal. Diurnal habits later returned around 50-45 million years ago with the appearance of Colubroidea — the family of snakes that now make up over 85% of living snake species. As colder night time temperatures may have limited nocturnal activity, the researchers say that the success of Colubroidea may have been facilitated by the return of these diurnal habits.

The results suggest that the success of snakes in occupying a range of habitats over their evolutionary history is partly due to their skills as ‘dispersers’. Snakes are estimated to be able to travel ranges up to 110,000 square kilometres, around 4.5 times larger than lizards. They are also able to inhabit environments that traditionally hinder the dispersal of terrestrial animals, having invaded aquatic habitats multiple times in their evolutionary history.

Journal Reference:

  1. Allison Y Hsiang, Daniel J Field, Timothy H Webster, Adam DB Behlke, Matthew B Davis, Rachel A Racicot, Jacques A Gauthier. The origin of snakes: revealing the ecology, behavior, and evolutionary history of early snakes using genomics, phenomics, and the fossil record. BMC Evolutionary Biology, 2015; 15 (1) DOI: 10.1186/s12862-015-0358-5

Citation: BioMed Central. “What did the first snakes look like?.” ScienceDaily. ScienceDaily, 19 May 2015. <www.sciencedaily.com/releases/2015/05/150519210253.htm>.

Probing iron chemistry in the deep mantle

Carbonates are a group of minerals that contain the carbonate ion (CO32-) and a metal, such as iron or magnesium. Carbonates are important constituents of marine sediments and are heavily involved in the planet’s deep carbon cycle, primarily due to oceanic crust sinking into the mantle, a process called subduction. During subduction, carbonates interact with other minerals, which alter their chemical compositions. The concentrations of the metals gained by carbonate ions during these interactions are of interest to those who study deep earth chemistry cycles.

Rearrangement of the electrons in iron upon pressure-induced spin transition in carbonates. Credit: Sergey Lobanov

Rearrangement of the electrons in iron upon pressure-induced spin transition in carbonates.
Credit: Sergey Lobanov

Carbonates were known to exist in the upper mantle due to their role in the deep carbon cycle. But it was thought that they could not withstand the more-extreme conditions of the lower mantle. Laboratory experiments and the discovery of tiny bits of carbonate impurities in lower mantle diamonds indicated that carbonates could withstand the extreme pressures and temperatures of not only the upper mantle, but the lower mantle as well.

Previous research had shown that upper mantle carbonates are magnesium-rich and iron-poor. Under lower mantle conditions, it is thought that the arrangement of electrons in carbonate minerals changes under the pressure stress in such a way that iron may be significantly redistributed. However, accurate observations of lower mantle carbonates’ chemical composition are not possible yet.

A research team–Carnegie’s Sergey Lobanov and Alexander Goncharov, along with Konstantin Litasov of the Russian Academy of Science and Novosibirsk State University in Russia–focused on the high-pressure chemistry of a carbonate mineral called siderite, which is an iron carbonate, FeCO3, commonly found in hydrothermal vents. Their findings help resolve questions about the presence of iron-containing lower mantle carbonates, and are published by American Mineralogist.

Until recently the electron-arrangement change responsible for iron redistribution in the lower mantle had not been measured in the lab. It was previously discovered that this change, a phenomenon called a spin transition, took place between about 424,000 and 484,000 times normal atmospheric pressure (43 to 49 gigapascals).The team was able to pinpoint that spin transition was occurring in iron carbonates under about 434,000 times normal atmospheric pressure (44 gigapascals), typical of the lower mantle.

A spin transition is a rearrangement of electrons in a molecule or a mineral. Electrons hold a compound’s atoms together by bonding. Certain fundamental rules of chemistry govern this bonding process, which have to do with the energy it takes to form the bonds. Pressure-induced spin transitions rearrange electrons and change the energy of the chemical bonds. If the change in chemical bond energy is high enough, the spin transition may trigger iron redistribution between coexisting minerals.

To quantify the energy change, siderite’s spin transition was examined using highly sensitive spectroscopic techniques at pressures ranging from zero to about 711,000 times normal atmospheric pressure (72 gigapascals), and also revealed by a visible color change after the transition, indicating rearrangement of electrons. The obtained spectroscopic data provided the key ingredient to estimating the carbonate composition at pressures exceeding the spin transition-pressure. It turned out that lower mantle carbonates should be iron-rich, unlike upper mantle carbonates. Similar effects may exist in other lower mantle minerals, if they also undergo spin transitions.

“As we learn more about how the spin transition affects chemical composition in carbonates, we improve our understanding of all iron-bearing minerals, enhancing our knowledge about lower mantle chemistry,” said Lobanov.

Citation: Carnegie Institution. “Probing iron chemistry in the deep mantle.” ScienceDaily. ScienceDaily, 15 May 2015. <www.sciencedaily.com/releases/2015/05/150515175100.htm>.

Digital dinosaurs: Restore dinosaur fossil

Fossils are usually deformed or incompletely preserved when they are found, after sometimes millions of years of fossilization processes. Consequently, fossils have to be studied very carefully to avoid damage, and are sometimes they are difficult to access, as they might be located in remote museum collections. An international team of scientists, led by Dr. Stephan Lautenschlager from the University of Bristol now solved some of these problems by using modern computer technology, as described in a recent issue of the Journal of Vertebrate Paleontology.

The team consisting of Dr. Stephan Lautenschlager and Professor Emily Rayfield from the University of Bristol, Professor Lindsay Zanno from the North Carolina Museum of Natural Sciences and North Carolina State University, Dr. Perle Altangerel from the National University of Ulaanbaatar, and Professor Lawrence Witmer from Ohio University employed high-resolution X-ray computed tomography (CT scanning) and digital visualisation techniques to restore a rare dinosaur fossil.

Lead author, Dr. Stephan Lautenschlager of Bristol’s School of Earth Sciences said: “With modern computer technology, such as CT scanning and digital visualisation, we now have powerful tools at our disposal, with which we can get a step closer to restore fossil animals to their life-like condition.”

The focus of the study was the skull of Erlikosaurus andrewsi, a 3-4m (10-13ft) large herbivorous dinosaur called a therizinosaur, which lived more than 90 million years ago during the Cretaceous Period in what is now Mongolia.

This image shows a comparison between originally preserved and digitally restored skull of the Cretaceous dinosaur Erlikosaurus andrewsi. – Image courtesy Journal of Vertebrate PaImage courtesy Journal of Vertebrate Paleontologyleontology

This image shows a comparison between originally preserved and digitally restored skull of the Cretaceous dinosaur Erlikosaurus andrewsi. – Image courtesy Journal of Vertebrate PaImage courtesy Journal of Vertebrate Paleontologyleontology

“The fossil skull of Erlikosaurus andrewsi is one-of-a-kind and the most complete and best preserved example known for this group of dinosaurs. As such it is of high scientific value” explains co-author Professor Emily Rayfield.

Using a digital model of the fossil, the team virtually disassembled the skull of Erlikosaurus into its individual elements. Then they digitally filled in any breaks and cracks in the bones, duplicated missing elements and removed deformation by applying retro-deformation techniques, digitally reversing the steps of deformation. In a final step, the reconstructed elements were re-assembled. This approach not only allowed the restoration of the complete skull of Erlikosaurus, but also the study of its individual elements.

However, using digital models has further advantages adds Dr. Lawrence Witmer: “Digital models allow the study of the external and internal features of a fossil. Furthermore, they can be shared quickly amongst researchers – without any risk to the actual fossil and without having to travel hundreds or even thousands of miles to see the original.”

Co-author, Dr. Lindsay Zanno agrees: “Therizinosaurs , with their pot bellies and comically enlarged claws, are arguably the most bizarre theropod dinosaurs. We know a lot about their oddball skeletons from the neck down, but this is the first time we’ve been able to digitally dissect an entire skull.”
Note: This story has been adapted from a news release issued by the Society of Vertebrate Paleontology

New evidence for combat and cannibalism in tyrannosaurs

A new study documents injuries inflicted in life and death to a large tyrannosaurine dinosaur. The paper shows that the skull of a genus of tyrannosaur called Daspletosaurus suffered numerous injuries during life, at least some of which were likely inflicted by another Daspletosaurus. It was also bitten after death in an apparent event of scavenging by another tyrannosaur. Thus there’s evidence of combat between two large carnivores as well as one feeding on another after death.

Daspletosaurus was a large carnivore that lived in Canada and was only a little smaller than its more famous cousin Tyrannosaurus. Like other tyrannosaurs it was most likely both an active predator and scavenger. The individual in question, from Alberta Canada, was not fully grown and would be considered a ‘sub-adult’ in dinosaur terms (approximately equivalent to an older teenager in human terms). It would have been just under 6 m long and around 500 kg when it died.

his is an artist's reconstruction of combat between two Daspletosaurus. Credit: Copyright Luis Rey

This is an artist’s reconstruction of combat between two Daspletosaurus.
Credit: Copyright Luis Rey

Researchers found numerous injuries on the skull that occurred during life. Although not all of them can be attributed to bites, several are close in shape to the teeth of tyrannosaurs. In particular one bite to the back of the head had broken off part of the skull and left a circular tooth-shaped puncture though the bone. The fact that alterations to the bone’s surface indicate healing means that these injuries were not fatal and the animal lived for some time after they were inflicted.

Lead author Dr David Hone from Queen Mary, University of London said “This animal clearly had a tough life suffering numerous injuries across the head including some that must have been quite nasty. The most likely candidate to have done this is another member of the same species, suggesting some serious fights between these animals during their lives.”

There is no evidence that the animal died at the hands (or mouth) of another tyrannosaur. However, the preservation of the skull and other bones, and damage to the jaw bones show that after the specimen began to decay, a large tyrannosaur (possibly of the same species) bit into the animal and presumably ate at least part of it.

Combat between large carnivorous dinosaurs is already known and there is already evidence for cannibalism in various groups, including tyrannosaurs. This is however an apparently unique record with evidence of both pre- and post-mortem injuries to a single individual.

Courtesy: PeerJ. “New evidence for combat and cannibalism in tyrannosaurs.” ScienceDaily. ScienceDaily, 9 April 2015. <www.sciencedaily.com/releases/2015/04/150409083201.htm>.

Swift Drift Of Indian Plate Explained

In the history of continental drift, India has been a mysterious record-holder.

More than 140 million years ago, India was part of an immense supercontinent called Gondwana, which covered much of the Southern Hemisphere. Around 120 million years ago, what is now India broke off and started slowly migrating north, at about 5 centimeters per year. Then, about 80 million years ago, the continent suddenly sped up, racing north at about 15 centimeters per year — about twice as fast as the fastest modern tectonic drift. The continent collided with Eurasia about 50 million years ago, giving rise to the Himalayas.

For years, scientists have struggled to explain how India could have drifted northward so quickly. Now geologists at MIT have offered up an answer: India was pulled northward by the combination of two subduction zones — regions in the Earth’s mantle where the edge of one tectonic plate sinks under another plate. As one plate sinks, it pulls along any connected landmasses. The geologists reasoned that two such sinking plates would provide twice the pulling power, doubling India’s drift velocity.

Himalayan mountain. Scientists found relics of what may have been two subduction zones by sampling and dating rocks from the Himalayan region. (stock image) Credit: © Maygutyak / Fotolia

Himalayan mountain. Scientists found relics of what may have been two subduction zones by sampling and dating rocks from the Himalayan region. (stock image)
Credit: © Maygutyak / Fotolia

The team found relics of what may have been two subduction zones by sampling and dating rocks from the Himalayan region. They then developed a model for a double subduction system, and determined that India’s ancient drift velocity could have depended on two factors within the system: the width of the subducting plates, and the distance between them. If the plates are relatively narrow and far apart, they would likely cause India to drift at a faster rate.

The group incorporated the measurements they obtained from the Himalayas into their new model, and found that a double subduction system may indeed have driven India to drift at high speed toward Eurasia some 80 million years ago.

“In earth science, it’s hard to be completely sure of anything,” says Leigh Royden, a professor of geology and geophysics in MIT’s Department of Earth, Atmospheric and Planetary Sciences. “But there are so many pieces of evidence that all fit together here that we’re pretty convinced.”

Royden and colleagues including Oliver Jagoutz, an associate professor of earth, atmospheric, and planetary sciences at MIT, and others at the University of Southern California have published their results this week in the journal Nature Geoscience.

What drives drift?

Based on the geologic record, India’s migration appears to have started about 120 million years ago, when Gondwana began to break apart. India was sent adrift across what was then the Tethys Ocean — an immense body of water that separated Gondwana from Eurasia. India drifted along at an unremarkable 40 millimeters per year until about 80 million years ago, when it suddenly sped up to 150 millimeters per year. India kept up this velocity for another 30 million years before hitting the brakes — just when the continent collided with Eurasia.

“When you look at simulations of Gondwana breaking up, the plates kind of start to move, and then India comes slowly off of Antarctica, and suddenly it just zooms across — it’s very dramatic,” Royden says.

In 2011, scientists believed they had identified the driving force behind India’s fast drift: a plume of magma that welled up from the Earth’s mantle. According to their hypothesis, the plume created a volcanic jet of material underneath India, which the subcontinent could effectively “surf” at high speed.

However, when others modeled this scenario, they found that any volcanic activity would have lasted, at most, for 5 million years — not nearly enough time to account for India’s 30 million years of high-velocity drift.

Squeezing honey

Instead, Royden and Jagoutz believe that India’s fast drift may be explained by the subduction of two plates: the tectonic plate carrying India and a second plate in the middle of the Tethys Ocean.

In 2013, the team, along with 30 students, trekked through the Himalayas, where they collected rocks and took paleomagnetic measurements to determine where the rocks originally formed. From the data, the researchers determined that about 80 million years ago, an arc of volcanoes formed near the equator, which was then in the middle of the Tethys Ocean.

A volcanic arc is typically a sign of a subduction zone, and the group identified a second volcanic arc south of the first, near where India first began to break away from Gondwana. The data suggested that there may have been two subducting plates: a northern oceanic plate, and a southern tectonic plate that carried India.

Back at MIT, Royden and Jagoutz developed a model of double subduction involving a northern and a southern plate. They calculated how the plates would move as each subducted, or sank into the Earth’s mantle. As plates sink, they squeeze material out between their edges. The more material that can be squeezed out, the faster a plate can migrate. The team calculated that plates that are relatively narrow and far apart can squeeze more material out, resulting in faster drift.

“Imagine it’s easier to squeeze honey through a wide tube, versus a very narrow tube,” Royden says. “It’s exactly the same phenomenon.”

Royden and Jagoutz’s measurements from the Himalayas showed that the northern oceanic plate remained extremely wide, spanning nearly one-third of the Earth’s circumference. However, the southern plate carrying India underwent a radical change: About 80 million years ago, a collision with Africa cut that plate down to 3,000 kilometers — right around the time India started to speed up.

The team believes the diminished plate allowed more material to escape between the two plates. Based on the dimensions of the plates, the researchers calculated that India would have sped up from 50 to 150 millimeters per year. While others have calculated similar rates for India’s drift, this is the first evidence that double subduction acted as the continent’s driving force.

“It’s a lucky coincidence of events,” says Jagoutz, who sees the results as a starting point for a new set of questions. “There were a lot of changes going on in that time period, including climate, that may be explained by this phenomenon. So we have a few ideas we want to look at in the future.”

Reference:

  1. Oliver Jagoutz, Leigh Royden, Adam F. Holt, Thorsten W. Becker. Anomalously fast convergence of India and Eurasia caused by double subduction. Nature Geoscience, 2015; DOI: 10.1038/ngeo2418
Citation :Massachusetts Institute of Technology. “Mystery of India’s rapid move toward Eurasia 80 million years ago explained.” ScienceDaily. ScienceDaily, 4 May 2015. <www.sciencedaily.com/releases/2015/05/150504120815.htm>.

Chicken Embryos With Dino Snouts ?

Chicks with dino-snouts? With a little molecular tinkering, for the first time scientists have created chicken embryos with broad, Velociraptor-like muzzles in the place of their beaks.

The bizarrely developing chickens shed new light on how the bird beak evolved, scientists added.

The Age of Dinosaurs came to an end with a bang about 65 million years ago, due to an impact from a giant rock from space, which was probably about 6 miles (10 kilometers) across. However, not all of the dinosaurs went extinct because of this catastrophe — birds, or avian dinosaurs, are now found on every continent on Earth..

Above is an artist rendition of the non-avian dinosaur Anchiornis (left) and a tinamou, a primitive modern bird (right), with snouts rendered transparent to show the premaxillary and palatine bones.

Above is an artist rendition of the non-avian dinosaur Anchiornis  with snouts rendered transparent to show the premaxillary and palatine bones.

“There are between 10,000 and 20,000 species of birds alive today, at least twice as many as the total number of mammal species, and so in many ways it is still the Age of Dinosaurs,” study lead author Bhart-Anjan Bhullar, a paleontologist and developmental biologist at Yale University, told Live Science.

Fossil discoveries have recently yielded great insights into how birds evolved from their reptilian ancestors, such as how feathers and flight emerged. Another key structure that sets birds apart from their dinosaurs ancestors is their beaks. Researchers suspect that beaks evolved to act like tweezers to give birds a kind of precision grip. The beaks help make up for the dinosaurs’ grasping arms, which evolved into wings, giving them the ability to peck at food such as seeds and bugs.

“The beak is a crucial part of the avian feeding apparatus, and is the component of the avian skeleton that has perhaps diversified most extensively and most radically — consider flamingos, parrots, hawks, pelicans and hummingbirds, among others,” Bhullar said in a statement. “Yet little work has been done on what exactly a beak is, anatomically, and how it got that way either evolutionarily or developmentally.”

To learn more about how the beak evolved, a research team led by Bhullar and developmental biologist Arkhat Abzhanov at Harvard University have now successfully reverted the beaks of chicken embryos into snouts more similar to ones seen in Velociraptor and Archaeopteryx than in birds. These embryos did not live to hatch, researchers stressed. “They could have,” Bhullar said. “They actually probably wouldn’t have done that badly if they did hatch. Mostly, though, we were interested in the evolution of the beak, and not in hatching a ‘dino-chicken’ just for the sake of it.”

Can skull shape and function determine what kind of food was on prehistoric plates?

When paleontologists put together a life history for a long-extinct animal, it’s common to infer the foods it ate by looking at modern animals with similar skull shapes and tooth patterns. But this practice is far from foolproof. New modeling and tests based on living species done at the American Museum of Natural History show that the link between animal diets and skull biomechanics is complex, with a stronger influence from ancestry than previously thought.

“Traditionally, when we looked at a fossilized skull with pointy piercing teeth and sharp slicing blades, we assumed that it was primarily a meat eater, but that simplistic line of thinking doesn’t always hold true,” said John J. Flynn, the Museum’s Frick Curator of Fossil Mammals and a co-author on the new work published today in the journal PLOS ONE. “We’ve found that diet can be linked to a number of factors–skull size, biomechanical attributes, and often, most importantly, the species’ position in the tree of life.”

Flynn and Z. Jack Tseng, a National Science Foundation and Frick Postdoctoral Fellow in the Museum’s Division of Paleontology, looked at the relationship between skull shape and function of five different modern carnivore species, including meat-eating “hypercarnivore” specialists such as wolves and leopards, and more omnivorous “generalists” such as mongooses, skunks, and raccoons. The initial modeling, which mapped bite force against the stiffness of the animal’s skull, yielded a surprise.

This image shows the skulls of the different species the researchers studied along with biomechanical profiles, which were made by mapping each animal's bite force against skull stiffness. They found that ancestry has a strong influence on the models, with closely related animals like leopards and mongooses grouping together, but also that predications about diet can be made based on the shape of the individual biomechanical profiles. Credit: Copyright AMNH/Z.-J. Tseng

This image shows the skulls of the different species the researchers studied along with biomechanical profiles, which were made by mapping each animal’s bite force against skull stiffness. They found that ancestry has a strong influence on the models, with closely related animals like leopards and mongooses grouping together, but also that predications about diet can be made based on the shape of the individual biomechanical profiles.
Credit: Copyright AMNH/Z.-J. Tseng

“Animals with the same diets and biomechanical demands, like wolves and leopards–both hypercarnivores–were not linking together,” Tseng said. “Instead, we saw a strong signal driven mostly by ancestry, where, for example, the leopard and the mongoose bind together because they’re more closely related in an evolutionary context, although they have very different dietary preferences and feeding strategies.”

But once Tseng and Flynn accounted for the strong effects of ancestry and skull size on the models, hypercarnivores and generalists still could be distinguished based on biomechanics, in particular by looking at where along the tooth row the skull is strongest. Meat specialist skulls are stiffest when hunting with front teeth and/or slicing or crushing with back teeth, whereas skulls of generalists show incrementally increasing stiffness when biting sequentially from the front to the back of the tooth row.

The researchers then applied this improved shape-function computer model to two extinct species: Thinocyon velox, a predatory mammal that was part of the now-extinct Creodont group, and Oodectes herpestoides, an early fossil predecessor of modern carnivores,. They found that T. velox likely had a unique hypercarnivorous feeding style that allowed for skull strength at two places: prey capture with its front teeth and powerful slicing and crushing with its back teeth. The biomechanical profile of O. herpestoides, meanwhile, suggests that it was a generalist, but compared to living relatives of similar body size, it might have fed on smaller prey because of its weaker skull.

“Beyond feeding adaptations of extinct species, we also want to decipher how adaptations evolved using reconstructed ancestors of living and fossil forms,” Tseng said. “We are applying similar types of skull shape and biomechanical analyses to reconstructed hypothetical ancestor skulls of Carnivora and their relatives to map out and better understand the long history of feeding adaptation of living top predators.”

Credits: American Museum of Natural History. (2015, April 29). Can skull shape and function determine what kind of food was on prehistoric plates?.ScienceDaily. Retrieved May 11, 2015 from www.sciencedaily.com/releases/2015/04/150429145448.htm

Explosive volcanoes fueled by water

University of Oregon geologists have tapped water in surface rocks to show how magma forms deep underground and produces explosive volcanoes in the Cascade Range.

“Water is a key player,” says Paul J. Wallace, a professor in the UO’s Department of Geological Sciences and coauthor of a paper in the May issue of Nature Geoscience. “It’s important not just for understanding how you make magma and volcanoes, but also because the big volcanoes that we have in the Cascades — like Mount Lassen and Mount St. Helens — tend to erupt explosively, in part because they have lots of water.”

A five-member team, led by UO doctoral student Kristina J. Walowski, methodically examined water and other elements contained in olivine-rich basalt samples that were gathered from cinder cone volcanoes that surround Lassen Peak in Northern California, at the southern edge of the Cascade chain.

Mount Hood, Oregon. Credit: © dschreiber29 / Fotolia

Mount Hood, Oregon.
Credit: © dschreiber29 / Fotolia

The discovery helps solve a puzzle about plate tectonics and Earth’s deep water cycle beneath the Pacific Ring of Fire, which scientists began studying in the 1960s to understand the region’s propensity for big earthquakes and explosive volcanoes. The ring stretches from New Zealand, along the eastern edge of Asia, north across the Aleutian Islands of Alaska and south along the coast of North and South America. It contains more than 75 percent of the planet’s volcanoes.

To understand how water affects subduction of the oceanic plate, in which layers of different rock types sink into the mantle, the UO team studied hydrogen isotopes in water contained in tiny blobs of glass trapped in olivine crystals in basalt.

To do so, the team used equipment in Wallace’s lab, CAMCOR, the Carnegie Institution in Washington, D.C., and a lab at Oregon State University. CAMCOR is UO’s Advanced Materials Characterization in Oregon, a high-tech extension service located in the underground Lorry I. Lokey Laboratories.

Next, the team fed data gained from the rocks into a complex computer model developed by co-author Ikudo Wada, then of Japan’s Tohoku University. She has since joined the University of Minnesota.

That combination opened a window on how rising temperatures during subduction drive water out of different parts of the subducted oceanic crust, Walowski said. Water migrates upwards and causes the top of the subducted oceanic crust to melt, producing magma beneath the Cascade volcanoes.

The key part of the study, Wallace said, involved hydrogen isotopes. “Most of the hydrogen in water contains a single proton,” he said. “But there’s also a heavy isotope, deuterium, which has a neutron in addition to the proton. It is important to measure the ratio of the two isotopes. We use this ratio as a thermometer, or probe, to study what’s happening deep inside the earth.”

“Melting of the subducting oceanic crust and the mantle rock above it would not be possible without the addition of water,” Walowski said. “Once the melts reach the surface, the water can directly affect the explosiveness of magma. However, evidence for this information is lost to the atmosphere during violent eruptions.”

University of Oregon. “Explosive volcanoes fueled by water.” ScienceDaily. ScienceDaily, 6 May 2015. <www.sciencedaily.com/releases/2015/05/150506125115.htm>

Archaeornithura meemannae : a new bird fossil

Scientists in China have described a new species of early bird, from two fossils with intact plumage dating to 130 million years ago.

Based on the age of the surrounding rocks, this is the earliest known member of the clade that produced today’s birds: Ornithuromorpha.It pushes back the branching-out of this evolutionary group by at least five million years.The little bird appears to have been a wader, capable of nimble flight.The discovery is reported in the journal Nature Communications.

Archaeornithura meemannae

Archaeornithura meemannae

Birds began to evolve from the dinosaurs some 150 million years ago at the tail end of the Jurassic period. This is the age of the famous but hotly contested “first bird” Archaeopteryx – now considered by many to be a feathered dinosaur.

Some 20 million years later, when the newfound species was wading and flitting through what would become north-eastern China, palaeontologists believe there was quite a variety of bird life.

Bare legs

About half of those species were Enantiornithes, a group of early birds with teeth and clawed wings that eventually all died out.

The other half, including the new find, were Ornithuromorpha – a group that eventually gave rise to modern birds and looked much more like them.The branching event behind that forked diversity is what the new discovery pushes back in time; previously the earliest known Ornithuromorph was 125 million years old.The well-preserved fossils included signs of the animal’s plumage

The pair of skeletons that define the new species, christened Archaeornithura meemannae, were dug up from the Sichakou basin in Hebei province.

“The new fossil represents the oldest record of Ornithuropmorpha,” said first author Wang Min, from the Chinese Academy of Sciences in Beijing. “It pushes back the origination date… by at least five million years.”

The specimens were well preserved, revealing a number of details about A. meemannae. The bird stood about 15cm tall and its legs, even on the upper regions, had no feathers, which suggests a wading lifestyle.The size and shape of its bones also suggest good manoeuvrability in the air.

Rupture along the Himalayan Front

In their article for Lithosphere on 12 March, authors Kristin Morell and colleagues write, “The ∼700-km-long ‘central seismic gap’ is the most prominent segment of the Himalayan front not to have ruptured in a major earthquake during the last 200-500 years. This prolonged seismic quiescence has led to the proposition that this region, with a population of more 10 million, is overdue for a great earthquake. Despite the region’s recognized seismic risk, the geometry of faults likely to host large earthquakes remains poorly understood.”

A little more than a month on, the area experience a magnitude 7.8 earthquake, centered in Nepal (25 Apr. 2015).

Date and rupture patches for large historical Himalayan earthquakes (Rajendran and Rajendran, 2005; Kumar et al., 2006) with reference to the Uttarakhand region of the central seismic gap, and the physiographic transition 2 of Uttarakhand (UPT2 ) and Nepal (NPT2 ) (Wobus et al., 2006a). (B) Simplified geologic map for area shown in A (Célérier et al., 2009a; Webb et al., 2011). Focal mechanisms of all earthquakes within the recording period (Mw 5-7) are shown with location as white circle. Earthquake locations are based on Ni and Baranzangi (1984) and the National Earthquake Information Center (NEIC) catalog (earthquake.usgs.gov). Focal mechanisms are based on Ni and Baranzangi (1984) or the Global Centroid-Moment-Tensor (CMT) catalog (globalcmt.org). STD--South Tibetan Detachment; THS--Tethyan Himalayan Sequence; MCT--Main Central Thrust; GHS--Greater Himalayan Sequence; LHS--Lesser Himalayan Sequence; MBT--Main Boundary Thrust; MFT--Main Frontal Thrust. Credit: Morell et al. and Lithosphere

Date and rupture patches for large historical Himalayan earthquakes (Rajendran and Rajendran, 2005; Kumar et al., 2006) with reference to the Uttarakhand region of the central seismic gap, and the physiographic transition 2 of Uttarakhand (UPT2 ) and Nepal (NPT2 ) (Wobus et al., 2006a). (B) Simplified geologic map for area shown in A (Célérier et al., 2009a; Webb et al., 2011). Focal mechanisms of all earthquakes within the recording period (Mw 5-7) are shown with location as white circle. Earthquake locations are based on Ni and Baranzangi (1984) and the National Earthquake Information Center (NEIC) catalog (earthquake.usgs.gov). Focal mechanisms are based on Ni and Baranzangi (1984) or the Global Centroid-Moment-Tensor (CMT) catalog (globalcmt.org). STD–South Tibetan Detachment; THS–Tethyan Himalayan Sequence; MCT–Main Central Thrust; GHS–Greater Himalayan Sequence; LHS–Lesser Himalayan Sequence; MBT–Main Boundary Thrust; MFT–Main Frontal Thrust.
Credit: Morell et al. and Lithosphere

In their study, Morell and colleagues use a series of complementary geomorphic and erosion rate data to define the ramp-flat geometry of the active detachment fault that is likely to host a large earthquake within the hinterland of the northwest Himalaya. Their analysis indicates that this detachment is sufficiently large to host another great earthquake in the western half of the central Himalayan seismic gap.

Specifically, their data sets point to a distinctive physiographic transition at the base of the high Himalaya in the state of Uttarakhand, India, characterized by abrupt strike-normal increases in channel steepness and a tenfold increase in erosion rates.

When combined with previously published geophysical imaging and seismicity data sets, Morell and colleagues interpret the observed spatial distribution of erosion rates and channel steepness to reflect the landscape response to spatially variable rock uplift due to a structurally coherent ramp-flat system of the Main Himalayan Thrust. They write, “Although it remains unresolved whether the kinematics of the Main Himalayan Thrust ramp involve an emergent fault or duplex, the landscape and erosion rate patterns suggest that the décollement beneath the state of Uttarakhand provides a sufficiently large and coherent fault segment capable of hosting a great earthquake.”

In conclusion, they note, “While this hypothesis remains speculative, it is supported by independent records of historical seismicity.”

Citation:Geological Society of America. “Rupture along the Himalayan Front.” ScienceDaily. ScienceDaily, 30 April 2015. <www.sciencedaily.com/releases/2015/04/150430134933.htm>.

Journal Ref: K. D. Morell, M. Sandiford, C. P. Rajendran, K. Rajendran, A. Alimanovic, D. Fink, J. Sanwal. Geomorphology reveals active decollement geometry in the central Himalayan seismic gap. Lithosphere, 2015; DOI: 10.1130/L407.1