Image of pregnant ichthyosaur with octuplets. Credit: Copyright Nobumichi Tamura
Palaeontologists have discovered part of the skeleton of a 180 million-year-old pregnant ichthyosaur with the remains of between six and eight tiny embryos between its ribs.
The new specimen was studied by palaeontologists Mike Boyd and Dean Lomax from The University of Manchester. It was collected around 2010 from near Whitby, North Yorkshire and is from the Early Jurassic. The fossil was in the collection of fossil collector, Martin Rigby, who thought the specimen might be a block of embryos. Dean confirmed the suspicion and the specimen was acquired by the Yorkshire Museum, York.
Ichthyosaurs were aquatic reptiles that dominated the Jurassic seas. They gave birth to live young, rather than laying eggs, and did not need to return to land, even to breed. They were carnivores, feeding upon other reptiles, fish, and marine invertebrates such as the squid-like belemnites.
Ichthyosaur fossils are quite common in the UK and often found in British Jurassic rocks. However, only five ichthyosaur specimens from Britain have ever been found with embryos and none with this many. All five were collected from Jurassic exposures in the south-west of England and are between 200-190 million years old. This is the first to be found in Yorkshire. The new specimen is a star attraction in the new major exhibition, Yorkshire’s Jurassic World, which recently opened on March 24.
The Jurassic rocks of Yorkshire have produced hundreds of ichthyosaur and other marine reptile skeletons, but have not, until now, yielded any reptilian embryos. The new specimen, as well as being the first embryo-bearing ichthyosaur recorded from Yorkshire, is also geologically the youngest of the British embryo-bearing specimens, being from the Toarcian Stage of the Jurassic, around 180 million-year-old.
The specimen is a small boulder that has been cut in half and polished, which exposes several large ribs (of the adult) and several strings of vertebrae and various indeterminate tiny bones. Boyd and Lomax say there are at least six embryos present, but probably eight.
Mike said: “We also considered the possibility that the tiny remains could be stomach contents, although it seemed highly unlikely that an ichthyosaur would swallow six to eight aborted embryos or newborn ichthyosaurs at one time. And this does not seem to have been the case, because the embryos display no erosion from stomach acids. Moreover, the embryos are not associated with any stomach contents commonly seem in Early Jurassic ichthyosaurs, such as the remains of squid-like belemnites.”
Eight different species of ichthyosaur have been documented with embryos. By far, the most commonly found ichthyosaur with embryos is Stenopterygius. Over a hundred specimens of Stenopterygius from Holzmaden and surrounding areas in Germany have been found with embryos, ranging from one to eleven in number.
“The German sites are approximately the same age as the new specimen from Whitby and it is possible that the new specimen is also Stenopterygius, but no identifiable features are preserved in the adult or embryos. Nonetheless, this is an important find.” added Dean.
Sarah King, curator of natural science at the Yorkshire Museum, said: “This is an incredible find and the research by Dean and Mike has helped us confirm it is the first example of fossilised ichthyosaur embryos to be found in Yorkshire. Its display in Yorkshire’s Jurassic World incorporates the latest digital technology to reveal the embryos and to explain the significance of the discovery. It also allows us to show a softer and more nurturing side to the Sea Dragons which were the top marine predator of their time.”
Reference:
Boyd, M. J. and Lomax, D. R. The youngest occurrence of ichthyosaur embryos in the UK: A new specimen from the Early Jurassic (Toarcian) of Yorkshire. Proceedings of the Yorkshire Geological Society, 2018 DOI: 10.1144/pygs2017-008
For centuries, the prevailing science has indicated that all of the nitrogen on Earth available to plants comes from the atmosphere. But a study from the University of California, Davis, indicates that more than a quarter comes from Earth’s bedrock.
The study, to be published April 6 in the journal Science, found that up to 26 percent of the nitrogen in natural ecosystems is sourced from rocks, with the remaining fraction from the atmosphere.
Before this study, the input of this nitrogen to the global land system was unknown. The discovery could greatly improve climate change projections, which rely on understanding the carbon cycle. This newly identified source of nitrogen could also feed the carbon cycle on land, allowing ecosystems to pull more emissions out of the atmosphere, the authors said.
“Our study shows that nitrogen weathering is a globally significant source of nutrition to soils and ecosystems worldwide,” said co-lead author Ben Houlton, a professor in the UC Davis Department of Land, Air and Water Resources and director of the UC Davis Muir Institute. “This runs counter the centuries-long paradigm that has laid the foundation for the environmental sciences. We think that this nitrogen may allow forests and grasslands to sequester more fossil fuel CO2 emissions than previously thought.”
Weathering Is Key
Ecosystems need nitrogen and other nutrients to absorb carbon dioxide pollution, and there is a limited amount of it available from plants and soils. If a large amount of nitrogen comes from rocks, it helps explain how natural ecosystems like boreal forests are capable of taking up high levels of carbon dioxide.
But not just any rock can leach nitrogen. Rock nitrogen availability is determined by weathering, which can be physical, such as through tectonic movement, or chemical, such as when minerals react with rainwater.
That’s primarily why rock nitrogen weathering varies across regions and landscapes. The study said that large areas of Africa are devoid of nitrogen-rich bedrock while northern latitudes have some of the highest levels of rock nitrogen weathering. Mountainous regions like the Himalayas and Andes are estimated to be significant sources of rock nitrogen weathering, similar to those regions’ importance to global weathering rates and climate. Grasslands, tundra, deserts and woodlands also experience sizable rates of rock nitrogen weathering.
Geology and Carbon Sequestration
Mapping nutrient profiles in rocks to their potential for carbon uptake could help drive conservation considerations. Areas with higher levels of rock nitrogen weathering may be able to sequester more carbon.
“Geology might have a huge control over which systems can take up carbon dioxide and which ones don’t,” Houlton said. “When thinking about carbon sequestration, the geology of the planet can help guide our decisions about what we’re conserving.”
Mysterious Gap
The work also elucidates the “case of the missing nitrogen.” For decades, scientists have recognized that more nitrogen accumulates in soils and plants than can be explained by the atmosphere alone, but they could not pinpoint what was missing.
“We show that the paradox of nitrogen is written in stone,” said co-leading author Scott Morford, a UC Davis graduate student at the time of the study. “There’s enough nitrogen in the rocks, and it breaks down fast enough to explain the cases where there has been this mysterious gap.”
In previous work, the research team analyzed samples of ancient rock collected from the Klamath Mountains of Northern California to find that the rocks and surrounding trees there held large amounts of nitrogen. With the current study, the authors built on that work, analyzing the planet’s nitrogen balance, geochemical proxies and building a spatial nitrogen weathering model to assess rock nitrogen availability on a global scale.
The researchers say the work does not hold immediate implications for farmers and gardeners, who greatly rely on nitrogen in natural and synthetic forms to grow food. Past work has indicated that some background nitrate in groundwater can be traced back to rock sources, but further research is needed to better understand how much.
Rewriting Textbooks
“These results are going to require rewriting the textbooks,” said Kendra McLauchlan, program director in the National Science Foundation’s Division of Environmental Biology, which co-funded the research. “While there were hints that plants could use rock-derived nitrogen, this discovery shatters the paradigm that the ultimate source of available nitrogen is the atmosphere. Nitrogen is both the most important limiting nutrient on Earth and a dangerous pollutant, so it is important to understand the natural controls on its supply and demand. Humanity currently depends on atmospheric nitrogen to produce enough fertilizer to maintain world food supply. A discovery of this magnitude will open up a new era of research on this essential nutrient.”
UC Davis Professor Randy Dahlgren in the Department of Land, Air and Water Resources co-authored the study.
The study was funded by the National Science Foundation’s Division of Earth Sciences and its Division of Environmental Biology, as well as the Andrew W. Mellon Foundation.
Reference:
B. Z. Houlton, S. L. Morford, R. A. Dahlgren. Convergent evidence for widespread rock nitrogen sources in Earth’s surface environment. Science, 2018; 360 (6384): 58 DOI: 10.1126/science.aan4399
The 170 million-year-old tracks were made in a muddy lagoon off the north-east coast of what is now the Isle of Skye Credit: University of Edinburgh/PA Wire
Scientists have discovered the biggest dinosaur site in Scotland on the Isle of Skye after stumbling across giant footprints fossilized into coastal rock.
The 70cm-wide footprints of massive sauropods are said to be roughly 170 million years old and were found by the University of Edinburgh’s School of GeoSciences in April.
The tracks shed light on dinosaur life in the Middle Jurassic, a period from which few fossils have survived.
The team of Scottish boffins were about to go home after a day in the field when they spotted the impressions in coastal rock quite by chance.
Dr Steve Brusatte told the Independent: “We noticed this depression in the rock that kind of looked like a pothole, and then we noticed another one and another one.
“They started to form this zig-zag pattern, and it dawned on us pretty quickly that these were the footprints – and the handprints – of these huge, long-necked sauropod dinosaurs.
“It was a chance discovery, we were more lucky than talented,” he added.
At the time the prints were made the area would have been the muddy bottom of a shallow lagoon, now long since turned to rock and often hidden by the tide.
The culprit is thought to have been a long-necked relative of the brontosaurus-type dinosaur.
Dr Tom Challands, also from the University of Edinburgh, told the Independent: “It is exhilarating to make such a discovery and being able to study it in detail, but the best thing is this is only the tip of the iceberg.
“I’m certain Skye will keep yielding great sites and specimens for years to come,” he said.
In August, a fossil foot suspected to be that of a small early ancestor of the ferocious Tyrannosaurus Rex was found on a Welsh beach.
Student paleontologist Sam Davies, who is in his third year at the University of Portsmouth, made the discovery while searching for fossils on the beach.
“It was pure luck that I found it. It was just sitting on top of a slab of rock,” Davis told the Guardian.
Experts believe the fossilized foot is from the same animal whose skeleton was found after a section of cliff broke away onto the beach last year. The local Jurassic cliffs are known to be a rich source of fossils.
The species lived around 200 million years ago, was only 19 inches tall and is a miniature version of the T-Rex.
Note: The above post is reprinted from materials provided by RT.
This image depicts a reconstruction of what the extinct monitor lizard might have looked like. The parietal and pineal foramina are visible on the overlaid skull. Credit: Senckenberg Gesellschaft für Naturforschung / Andreas Lachmann / Digimorph.org
Researchers reporting in Current Biology on April 2 have evidence that an extinct species of monitor lizard had four eyes, a first among known jawed vertebrates. Today, only the jawless lampreys have four eyes.
The third and fourth eyes refer to pineal and parapineal organs, eye-like photosensory structures on the top of the head that play key roles in orientation and in circadian and annual cycles. The new findings help to elucidate the evolutionary history of these structures among vertebrates.
The photosensitive pineal organ is found in a number of lower vertebrates such as fishes and frogs, the researchers explain. It’s often referred to as the “third eye” and was widespread in primitive vertebrates.
“On the one hand, there was this idea that the third eye was simply reduced independently in many different vertebrate groups such as mammals and birds and is retained only in lizards among fully land-dwelling vertebrates,” says Krister Smith at the Senckenberg Research Institute in Germany. “On the other hand, there was this idea that the lizard third eye developed from a different organ, called the parapineal, which is well developed in lampreys. These two ideas didn’t really cohere.
“By discovering a four-eyed lizard — in which both pineal and parapineal organs formed an eye on the top of the head — we could confirm that the lizard third eye really is different from the third eye of other jawed vertebrates,” Smith continues.
Smith and his colleagues got the idea that the fossilized lizards might have a fourth eye after other experts came to contradictory conclusions about where the lizard’s third eye was located.
Smith said that the first question to explore the “wacky” idea of a lizard with four eyes was, does this unusual feature occur in more than one individual of the same age? They turned to museum specimens collected nearly 150 years ago at Grizzly Buttes as part of the Yale College Expedition to the Bridger Basin, Wyoming. And, it turned out that the answer to their question was yes. CT scans showed that two different individuals had spaces where a fourth eye would have been, which, Smith says, “I certainly did not expect!”
Their evidence confirms that the pineal and parapineal glands weren’t a pair of organs in the way that vertebrate eyes are. They also suggest that the third eye of lizards evolved independently of the third eye in other vertebrate groups.
Smith says that while there’s “nothing mystical” about the pineal and parapineal organs, they do enable extraordinary abilities. For instance, they allow some lower vertebrates to sense the polarization of light and use that information to orient themselves geographically.
Scientists still have a lot to learn about the evolution of these organs and their functions in living animals, the researchers say. The new findings are a reminder of the hidden value within fossils left lying around in museums for more than a century.
“The fossils that we studied were collected in 1871, and they are quite scrappy — really banged up,” Smith says. “One would be forgiven for looking at them and thinking that they must be useless. Our work shows that even small, fragmentary fossils can be enormously useful.”
Reference:
Krister T. Smith, Bhart-Anjan S. Bhullar, Gunther Köhler, Jörg Habersetzer. The Only Known Jawed Vertebrate with Four Eyes and the Bauplan of the Pineal Complex. Current Biology, 2018; 28 (7): 1101 DOI: 10.1016/j.cub.2018.02.021
A recent study led by UMass Amherst looked at risk in southeast Japan after the devastating 2011 quake and tsunami. The Japanese government called for hazard-assessment research to define the nation’s worst-case scenarios. Study centered on the Nankai Trough, a fault predicted to generate a magnitude 8 to 9 earthquake in coming decades. Credit: UMass Amherst
Geoscience researchers at the University of Massachusetts Amherst, Smith College and the Japanese Agency for Marine-Earth Science and Technology this week unveiled new, GPS-based methods for modeling earthquake-induced tsunamis for southeast Japan along the Nankai Trough. A Nankai-induced tsunami is likely to hit there in the next few decades, says lead author Hannah Baranes at UMass Amherst, and has the potential to displace four times the number of people affected by the massive Tohoku tsunami of 2011.
She and her doctoral advisor Jonathan Woodruff, with Smith College professor Jack Loveless and Mamoru Hyodo at the Japanese agency report details in the current Geophysical Research Letters. Baranes says, “We hope our work will open the door for applying similar techniques elsewhere in the world.”
As she explains, after the unexpectedly devastating 2011 quake and tsunami, Japan’s government called for hazard-assessment research to define the nation’s worst-case scenarios for earthquakes and tsunamis. Baranes notes, “The government guideline has focused attention on the Nankai Trough. It’s a fault offshore of southern Japan that is predicted to generate a magnitude 8 to 9 earthquake within the next few decades.”
The team’s research, supported by the National Science Foundation and a NASA graduate fellowship, began with a study of coastal lake sediments in Japan to establish long-term records of tsunami flooding. Between 2012 and 2014, Baranes and Woodruff collected sediment cores from lakes, looking for marine sand layers washed onshore by past extreme coastal floods. “These sand deposits get trapped and preserved at the bottoms of coastal lakes,” she says. “We can visit these sites hundreds or even thousands of years later and find geologic evidence for past major flood events.”
Results from Lake Ryuuoo, a small lake on an island in the Bungo Channel, show a surprising sand layer washed into Lake Ryuuoo by seawater rushing over a 13-foot-high barrier beach. “We were able to date the layer to the early 1700s, which is consistent with the known Nankai Trough tsunami event of record from 1707,” Baranes says.
She adds, “We were a bit puzzled. The Bungo Channel is tucked between two of Japan’s main islands and is relatively sheltered from Nankai Trough-generated tsunamis. Given recent tsunamis in the region, a minimum 13-foot tsunami in the channel seemed very unlikely.” Further, she points out, the Bungo Channel area today has much sensitive and critical infrastructure, including the only nuclear power plant on the island of Shikoku. This gave the researchers “particular concern” for tsunami hazard there, so they decided to investigate their original finding further using numerical modeling techniques.
As Baranes explains, an earthquake is caused by plates slipping past each other along faults in the earth’s crust. That slip causes the earth’s surface to deform, to uplift in some places and sink, or subside, in others. “When earthquake-induced uplift occurs on the sea floor, it displaces the entire column of water above it and generates the wave that we call a tsunami,” she adds. “We can simulate that process with numerical models.”
She and Woodruff tried using one of the most widely-cited models for the 1707 Nankai Trough earthquake to flood Lake Ryuuoo, but this only generated a six-foot tsunami that came nowhere near overtopping the 13-foot barrier beach.
“At that point, we were still stumped,” says Baranes. “But it wasn’t long before we had a stroke of good luck in learning that a leading expert on tectonic modeling in Japan, Jack Loveless, is a professor just down the road at Smith College.” Loveless uses very precise GPS measurements of earth surface motion to model the extent and spatial distribution of frictional locking that causes fault stress to build up between earthquakes.
With Loveless, the team created earthquake scenarios based on GPS estimates of present-day frictional locking along the Nankai Trough and for the first time rigorously tested methods for creating potential future earthquake scenarios from the GPS measurements. They tested various methods for creating a suite of GPS-based earthquake scenarios and simulated the resulting ground surface displacement and tsunami inundation.
Baranes reports that they found GPS measurements of present-day earth surface motion around the Nankai Trough yield an earthquake of a similar magnitude and extent as the 1707 event, and their simulated tsunami heights are consistent with historical accounts of the 1707 event. As for matching the Lake Ryuuoo geologic record, she adds, “Our model earthquake scenarios showed the Bungo Channel region subsiding seven feet and lowering Lake Ryuuoo’s barrier beach from 13 to six feet, such that a tsunami with a feasible height for an inland region easily flooded the lake.”
Woodruff, who conducted the study as part of a Fulbright fellowship, says, “Although our methodology was well received, our result for the Bungo Channel was met with a lot of skepticism. We needed to find an independent method for validating it.” They enlisted Hyodo, who had previously published earthquake scenarios based on models of the Nankai Trough’s physical characteristics. His physical model yielded the same focused subsidence in the Bungo Channel, Woodruff reports.
Baranes adds, “His model was also consistent with our GPS-based model in terms of earthquake magnitude, ground surface displacement and tsunami inundation. This was a really neat result because in addition to providing an independent line of evidence for significant tsunami hazard in the Bungo Channel, we demonstrated a connection between the Nankai Trough’s physical characteristics and GPS measurements of surface motion.”
Reference:
H. Baranes, J. D. Woodruff, J. P. Loveless, M. Hyodo. Interseismic Coupling-Based Earthquake and Tsunami Scenarios for the Nankai Trough. Geophysical Research Letters, 2018; DOI: 10.1002/2018GL077329
Mount Etna. Credit: BenAveling (Own work) via Wikimedia Commons
The iconic cone-like structure of Mount Etna could have been created after water levels in the Mediterranean Sea rose following an extended period of deglaciation, according to new research.
A study by Iain Stewart, Professor of Geoscience Communication at the University of Plymouth, explores changes in the volcano’s structures which began around 130,000 years ago.
Scientists have previously said the switch from a fissure-type shield volcano to an inland cluster of nested stratovolcanoes was caused by a tectonically driven rearrangement of major border faults.
However Professor Stewart, writing in Episodes, has suggested the change coincides closely with a period of particularly high sea levels that could have triggered the fundamental change in Mount Etna’s magmatic behaviour.
He also believes such a phenomenon could also explain changes at other volcanic sites across the world including the similarly iconic Stromboli, just off the north coast of Sicily, and even the volcano on Montserrat in the Caribbean.
Professor Stewart, who fronted the BBC documentary Volcano Live in 2013, said: “Mount Etna is arguably one of the most iconic volcanoes on the planet, but 100,000 years ago there would have been no cone-like structure such as you see today. I had always been interested to know what prompted that to happen but I believe the dates of sea levels rising — and how they correspond to the volcano physically changing — offer a potential explanation. The precise sensitivities of the plumbing beneath Etna has always been something of a mystery, but exploring how sea levels interact with its fault lines could shed new light on its creation and future.”
Mount Etna’s eruptive history began around 500,000 years ago with submarine volcanism. But this changed around 220,000 years ago into fissure type activity which built a north-south chain of eruptive centres along the present coastline.
This ultimately created a broad shield volcano immediately east of Etna’s coastline, which ceased around 130,000 years ago at the same time as the sea reached its highest levels following a period of deglaciation starting almost 12,000 years earlier.
However, Professor Stewart believes that over a few millennia those sea level rises could have caused the fault system beneath and around Mount Etna to completely change in behaviour, sealing up old lava flows and ultimately forcing them to emerge elsewhere on the island.
This ultimately created the iconic cone structure visible today, with Europe’s most active volcano still continuing to erupt tens of thousands of years later.
This new research has been published days after another study showed that Etna is edging towards the Mediterranean at a rate of around 14mm per year.
Professor Stewart added: “The latest measurements of Etna’s seaward slide give us a much better understanding of just how unstable Europe’s biggest volcano is. But the big question remains: what is driving that instability? For me, the fact that Etna’s dramatic switches in eruptive behaviour coincide with past abrupt changes in ocean levels implies that Etna’s antics are at least in part orchestrated by fluctuating waters of the Mediterranean Sea.”
Reference:
Iain Stewart. Did sea-level change cause the switch from fissure-type to central- type volcanism at Mount Etna, Sicily? Episodes, 2018; 41 (1): 7 DOI: 10.18814/epiiugs/2018/v41i1/018002
Credit: Andrew McAfee, Carnegie Museum of Natural History
The new predatory dinosaur Tratayenia rosalesi crosses a stream in what is now Patagonia, Argentina roughly 85 million years ago.
Although many new dinosaur species have been discovered over the past few decades, entire groups of these animals remain shrouded in mystery. One of these is the Megaraptoridae, a shadowy pack of predators that terrorized South America and Australia during the middle and late stages of the Cretaceous Period – the third and final time period of the Age of Dinosaurs. Today, paleontologists announced the discovery of a never-before-seen member of this motley crew that casts light on the skeletal structure of megaraptorids and the roles they played in their long-vanished environments. Named Tratayenia rosalesi, the new species is based on fossil bones collected in Neuquén Province, Argentina – located in the northern part of the wild, windswept region of South America known as Patagonia. A study of the new creature—named after the locality where it was found, Tratayén, and its discoverer, Argentine fossil hunter Diego Rosales—was recently published in the scientific journal Cretaceous Research.
According to study leader Juan Porfiri of the Museo de Ciencias Naturales of the Universidad Nacional del Comahue in Neuquén, “When Diego told us about his find, we quickly got permission from the Dirección Provincial de Patrimonio Cultural del Neuquén to dig up the dinosaur. After we went to the site and began to unearth the bones, we got very excited because we thought we might have a megaraptorid.”
Says study co-author Domenica dos Santos, also of the Museo de Ciencias Naturales of the Universidad Nacional del Comahue, “Not many megaraptorid specimens are known, so we thought the new fossil would provide important information on these enigmatic predators.” Adds fellow co-author Rubén Juárez Valieri of the Museo Provincial Carlos Ameghino in Cipolletti, Argentina, “Patagonian discoveries such as Tratayenia are expanding our knowledge of the spectacular but still mysterious dinosaurs of the Southern Hemisphere.”
The new predatory dinosaur Tratayenia rosalesi crosses a stream in what is now Patagonia, Argentina roughly 85 million years ago.
Although many new dinosaur species have been discovered over the past few decades, entire groups of these animals remain shrouded in mystery. One of these is the Megaraptoridae, a shadowy pack of predators that terrorized South America and Australia during the middle and late stages of the Cretaceous Period – the third and final time period of the Age of Dinosaurs. Today, paleontologists announced the discovery of a never-before-seen member of this motley crew that casts light on the skeletal structure of megaraptorids and the roles they played in their long-vanished environments. Named Tratayenia rosalesi, the new species is based on fossil bones collected in Neuquén Province, Argentina – located in the northern part of the wild, windswept region of South America known as Patagonia. A study of the new creature—named after the locality where it was found, Tratayén, and its discoverer, Argentine fossil hunter Diego Rosales—was recently published in the scientific journal Cretaceous Research.
According to study leader Juan Porfiri of the Museo de Ciencias Naturales of the Universidad Nacional del Comahue in Neuquén, “When Diego told us about his find, we quickly got permission from the Dirección Provincial de Patrimonio Cultural del Neuquén to dig up the dinosaur. After we went to the site and began to unearth the bones, we got very excited because we thought we might have a megaraptorid.”
Says study co-author Domenica dos Santos, also of the Museo de Ciencias Naturales of the Universidad Nacional del Comahue, “Not many megaraptorid specimens are known, so we thought the new fossil would provide important information on these enigmatic predators.” Adds fellow co-author Rubén Juárez Valieri of the Museo Provincial Carlos Ameghino in Cipolletti, Argentina, “Patagonian discoveries such as Tratayenia are expanding our knowledge of the spectacular but still mysterious dinosaurs of the Southern Hemisphere.”
Still, scientists have much left to learn about megaraptorids. For one thing, their evolutionary relationships to other meat-eating dinosaurs are poorly understood, with some scientists arguing that megaraptorids are related to even larger Southern Hemisphere carnivores such as Carcharodontosaurus and Giganotosaurus, whereas others contend that megaraptorids are close cousins of T. rex. Though Tratayenia does not help to solve this particular riddle, an answer may well be in sight. According to Porfiri, “Tratayenia is just one of many exciting megaraptorid fossils that have been found in recent years. After these specimens are studied, many questions surrounding these puzzling meat-eaters may finally be answered.”
Reference:
Juan D. Porfiri et al. A new megaraptoran theropod dinosaur from the Upper Cretaceous Bajo de la Carpa Formation of northwestern Patagonia, Cretaceous Research (2018). DOI: 10.1016/j.cretres.2018.03.014
Calbuco’s April 2015 eruption was its first activity since 1972. Credit: iStock
To borrow from a philosophical thought experiment: If a volcano erupts in a remote part of the world and no one hears it, does it still make a sound?
Indeed, it does. And not only does the sound occur, but it also can tell scientists about the timing and duration of the eruption itself.
As part of the United Nations’ Comprehensive Nuclear-Test-Ban Treaty, an International Monitoring System was built to detect any nuclear explosion on Earth — underground, underwater or in the atmosphere. Within that system is a network to detect atmospheric infrasound — sound waves with frequencies below the lower limit of human audibility — which scientists can also use to track volcanic eruptions in remote locations.
A new case study by an international team of scientists, led by UC Santa Barbara geophysicist Robin Matoza, examined data from the 2015 eruption of the Calbuco volcano in the Los Lagos Region of Chile. The researchers chose this event because they could compare long-range data with local readings, enabling study of the large volcanic explosion using infrasound sensors.
The team’s analysis demonstrated that infrasound recorded at regional (15 to 250 kilometers) and long distances (greater than 250 km), such as on the International Monitoring System, delivered similar constraints on the timing and duration of the eruption, as did data from a local (less than 15 km) seismic network. Their results appear in the Journal of Geophysical Research: Solid Earth.
“We want to be able to monitor regions in the world where many volcanoes do not have local monitoring stations like Calbuco does,” said Matoza, an assistant professor in UCSB’s Department of Earth Science. “In some places — for example, the Aleutian Islands in Alaska — it’s challenging to maintain observation networks on the volcanoes themselves due to harsh weather and their remote locations. Consequently, many Aleutian volcanoes are not instrumented. We want to be able to detect, locate and characterize remote explosive volcanic activity because eruptions can release ash clouds into the atmosphere, which are hazardous to aircraft.”
In remote locales, researchers usually rely on satellite-based technology to monitor volcanoes, but according to Matoza, without ground-based information, it’s difficult to know exactly when the eruption happened and how long it lasted.
“What’s nice about infrasound is that we are able to gather information farther from the source than with traditional ground-based monitoring methods,” Matoza explained. “Typically, seismic signals from eruptions don’t propagate more than a few hundred kilometers from the source. With Calbuco, for example, you can see the eruption very clearly on the local monitoring stations and out to about 250 kilometers on regional seismic networks, but with infrasound, the signal propagates in the atmosphere for more than 5,000 kilometers. What’s more, infrasound delivers different information than seismic data alone.”
The Chilean national seismic network includes a relatively sparse number of infrasound sensors co-located with 10 seismometers (seismo-acoustic stations), which enabled this study. Placing such infrasound sensors at more seismic stations in volcanically active regions would be valuable, Matoza noted. The fact that one of the Chilean seismo-acoustic stations was only 250 kilometers from the eruption highlights the significant potential of existing regional seismic networks for augmenting the International Monitoring System with more infrasound sensors for eruption detection and monitoring.
“One of the recommendations from this study is that more seismic networks should also have infrasound sensors,” Matoza said. “It’s one extra channel of data to record that provides very useful information for improving volcano monitoring.”
Reference:
Robin S. Matoza, David Fee, David Green, Alexis Le Pichon, Julien Vergoz, Matthew M. Haney, T. Dylan Mikesell, Luis Franco, O. Alberto Valderrama, Megan R. Kelley, Kathleen McKee, Lars Ceranna. Local, regional, and remote seismo-acoustic observations of the April 2015 VEI 4 eruption of Calbuco volcano, Chile. Journal of Geophysical Research: Solid Earth, 2018; DOI: 10.1002/2017JB015182
Scientists from the University of Aberdeen have created the world’s first 3D thermal image of an active volcano.
The spectacular image of Stromboli in Italy was made using high-precision cameras mounted to an aerial drone.
The image was created by a team of geoscientists from the Universities of Aberdeen and Oslo who are using drone technology to develop a technique that can detect subtle changes in the behaviour of the volcano, providing more accurate information on the likelihood of an eruption.
The first stage of the project was to develop a system for building 3D thermal models from an active volcano using drones.
This system was tested on the island of Stromboli in the Mediterranean. They have made a short video documenting there work and the results, with some spectacular drone footage of erupting volcanos and a 3D thermal model.
In the 1960s, some 50 years after German researcher Alfred Wegener proposed his continental drift hypothesis, the theory of plate tectonics gave scientists a unifying framework for describing the large-scale motion of the surface plates that make up the Earth’s lithosphere—a framework that subsequently revolutionized the geosciences.
How those plates move around the Earth’s surface is controlled by motion within the mantle—the driving force of which is convection due to thermal anomalies, with compositional heterogeneity also expected. However, the technical challenge of visualizing structures inside an optically impenetrable, 6,371-kilometer-radius rock sphere has made understanding the compositional and thermal state of the mantle, as well as its dynamic evolution, a long-standing challenge in Earth science.
Now, in a paper published today in Nature Communications, researchers from MIT, Imperial College, Rice University, and the Institute of Earth Sciences in France report direct evidence for lateral variations in mantle composition below Hawaii. The results provide scientists with important new insights into how the Earth has evolved over its 4.5 billion year history, why it is as it is now, and what this means for rocky planets elsewhere.
Compositional variation
Scientists treat the mantle as two layers—the lower mantle and the upper mantle—separated by a boundary layer termed the mantle transition zone (MTZ). Physically, the MTZ is bounded by two seismic-velocity discontinuities near 410 km and 660 km depth (referred to as 410 and 660). These discontinuities, which are due to phase transitions in silicate minerals, play an important role in modulating mantle flow. Lateral variations in depth to these discontinuities have been widely used to infer thermal anomalies in the mantle, as mineral physics predicts a shallower 410 and a deeper 660 in cold regions and a deeper 410 and a shallower 660 in hot regions.
Previous petrological and numerical studies also predict compositional segregation of basaltic and harzburgitic material (and thus compositional heterogeneity) near the base of the MTZ in the relatively warm low-viscosity environments near mantle upwellings. But observational evidence for such a process has been scarce.
The new study, however, demonstrates clear evidence for lateral variation in composition near the base of the MTZ below Hawaii. This evidence could have important implications for our general understanding of mantle dynamics.
As lead author Chunquan Yu Ph.D. ’16, a former grad student in the Hilst Group at MIT who is now a postdoc at Caltech, explains, “At middle ocean ridges, plate separation results in ascending and partial melting of the mantle material. Such a process causes differentiation of the oceanic lithosphere with basaltic material in the crust and harzburgitic residue in the mantle. As the differentiated oceanic lithosphere cools, it descends back into the mantle along the subduction zone. Basalt and harzburgite are difficult to separate in cold environments. However, they can segregate in relative warm low-viscosity environments, such as near mantle upwellings, potentially providing a major source of compositional heterogeneity in the Earth’s mantle.”
Looking with earthquakes
To explore this idea, Yu and his colleagues used a seismic technique involving the analysis of underside shear wave reflections off mantle discontinuities—known as SS precursors—to study MTZ structures beneath the Pacific Ocean around Hawaii.
“When an earthquake occurs, it radiates both compressional (P) and shear wave (S) energy. Both P and S waves can reflect from interfaces in the Earth’s interior,” Yu explains. “If an S wave leaves a source downward and reflects at the free surface before arriving at the receiver, it is termed SS. SS precursors are underside S-wave reflections off mantle discontinuities. Because they travel along shorter ray paths, they are precursory to SS.”
Using a novel seismic array technique, the team were able to improve the signal-to-noise ratio of the SS precursors and remove interfering phases. As a result, much more data that otherwise would have been discarded became accessible for analysis.
They also employed so-called amplitude versus offset analysis, a tool widely used in exploration seismology, to constrain elastic properties near MTZ discontinuities.
The analysis finds strong lateral variations in radial contrasts in mass density and wavespeed across 660 while no such variations were observed along the 410. Complementing this, the team’s thermodynamic modeling, along a range of mantle temperatures for several representative mantle compositions, precludes a thermal origin for the inferred lateral variations in elastic contrasts across 660. Instead, the inferred 660 contrasts can be explained by lateral variation in mantle composition: from average (pyrolytic; about 60 percent olivine) mantle beneath Hawaii to a mixture with more melt-depleted harzburgite (about 80 percent olivine) southeast of the hotspot. Such compositional heterogeneity is consistent with numerical predictions that segregation of basaltic and harzburgitic material could occur near the base of the MTZ near hot deep mantle upwellings like the one that is often invoked to cause volcanic activity on Hawaii.
“It has been suggested that compositional segregation between basaltic and harzburgitic materials could form a gravitationally stable layer over the base of the MTZ. If so it can provide a filter for slab downwellings and lower-mantle upwellings, and thus strongly affect the mode of mantle convection and its chemical circulation,” says Yu.
This study presents a promising technique to get constraints on the thus far elusive distribution of compositional heterogeneity within Earth’s mantle. Compositional segregation near the base of the MTZ has been expected since the 1960s and evidence that this process does indeed occur has important implications for our understanding of the chemical evolution of the Earth.
Reference:
“Compositional heterogeneity near the base of the mantle transition zone beneath Hawaii” Nature Communications (2018). DOI: 10.1038/s41467-018-03654-6
Back at the lab, the researchers found the fossil glowed under a black light. Credit: University of Kansas
For now, there are just a few things researchers and students at the University of Kansas want people to dig about the new dinosaur they recently excavated in Montana’s Hell Creek Formation.
First off, it’s a “fabulous” complete section of the upper jaw with all of its teeth intact, along with bits of the specimen’s skull, foot, hips and backbones. It’s likely to be the rare fossilized remains of a young Tyrannosaurus rex that lived 66.5 million years ago. But it also could be another species of smaller meat-eating dinosaur (it’s a bit of a scientific controversy)—they’re still analyzing their discovery.
Careful, microscopic preparation of its fragile bones is beginning to reveal important information that will help unravel the life history of Tyrannosaurus rex.
Other young tyrannosaur specimens have been recovered over the years, but since animal skeletons change shape as they grow, some confusion as to their evolutionary relationships has ensued. Some paleontologists think the young ones may represent different species, while other workers have suggested they all represent different growth stages of one species—Tyrannosaurus rex.
KU’s new specimen has the information that may provide the deciding factor of which theory is correct.
Researchers believe the specimen is a young Tyrannosaurus rex but are still conducting their analysis to be sure. They expect to publish their findings in the coming months.
“The teeth suggest it’s a Tyrannosaurus rex; however, there is still more work to be done,” said David Burnham, preparator of vertebrate paleontology at the KU Biodiversity Institute. “Because a young T. rex is so rare, there are only a few that have been found over the years, so it’s difficult to discern what are changes due to growth or if the differences in the bones reflect different species. Fortunately, KU has an older T. rex to compare with and another young T. rex on loan to help decipher this problem.”
One possibility is the specimen represents another carnivorous dinosaur dubbed a Nanotyrannus that likewise was discovered in the Hell Creek Formation and described by other scientists. The Nanotyrannus is a subject of controversy because it may represent a separate species, or it may be a juvenile Tyrannosaurus rex.
“Confusing the issue here is age,” Burnham said. “Ontogeny, that’s the process of growth—and during that process we change. Adult dinosaur bones, especially in the skull, don’t look the same as their younger selves. So, if someone finds a baby or juvenile fossil they may think it’s a new species, but we have to be careful since it may represent a younger growth stage of an existing species. It’s reasonable to assume Nanotyrannus could be valid—but we must show it’s not just a stage in the life history of T. rex.”
For now, Burnham and his team are analyzing the bones they have back in the lab and planning a return to Hell Creek to conduct fieldwork and search for more of the fossil.
“We’re going to go back out this summer—we’re going right to that spot,” said the KU researcher. “We think and hope there’s more there.”
In the meantime, Burnham and his fellow researchers (including Kyle Atkins-Weltman, graduate student and assistant fossil preparator) are working on a paper that will address the question of their fossil’s place in the family tree of theropod dinosaurs.
“With the specimens here at KU, we’ll be able to address the issue and make a declarative statement about Nanotyrannus,” Burnham said.
A new species of scorpionfly fossil from 53 million years ago at McAbee, British Columbia named Eomerope eonearctica. This insect is very similar to a fossil species that lived at the same time north of Vladivostok on the Asian Pacific coast, highlighting connections between Canada and Russia in ancient times. Credit: SFU
A new 53 million-year-old insect fossil called a scorpionfly discovered at B.C.’s McAbee fossil bed site bears a striking resemblance to fossils of the same age from Pacific-coastal Russia, giving further evidence of an ancient Canada-Russia connection.
“We’ve seen this connection before through fossil plants and animals, but these insects show this in a beautiful way,” says Bruce Archibald, a research associate in SFU’s Department of Biological Sciences and the Royal BC Museum. “They are so much alike that only the wing colour of the new McAbee species tells them apart.” Archibald and Alexandr Rasnitsyn, of Moscow’s Russian Academy of Sciences, described the find and its significance in this month’s The Canadian Entomologist.
“I’m not aware of any case where two such species so much alike and so close in age have been found in both Pacific Russia and Pacific Canada, and that’s pretty great,” said Archibald. He notes that the insect’s only living relative is found in the temperate forest of central Chile, which has a climate that is similar in ways to B.C.’s 53 million years ago.
The new Canadian species was named Eomerope eonearctica, and its Russian doppelganger is Eomerope asiatica, described in 1974. The McAbee fossil site has been designated a provincial heritage by the province of B.C. for its spectacular fossil record. Archibald and Rasnitsyn also described a second new scorpionfly species that was found near Princeton, B.C.
Reference:
S. Bruce Archibald, Alexandr P. Rasnitsyn. Two new species of fossil Eomerope (Mecoptera: Eomeropidae) from the Ypresian Okanagan Highlands, far-western North America, and Eocene Holarctic dispersal of the genus. The Canadian Entomologist, 2018; 1 DOI: 10.4039/tce.2018.13
Last week, a new species of dinosaur was described in the Journal of Vertebrate Paleontology. The dinosaur, Arkansaurus fridayi, is an ornithomimosaur the Early Cretaceous of Arkansas, and represents the first dinosaur to be described from that state. In fact, it’s now be honored as the State Dinosaur of Arkansas. And although the paper itself is not Open Access, the data is Open Access and can be found online at MorphoSource.
The specimen of Arkansaurus was discovered over four decades ago, and I sensed an interesting story behind this discovery. So I asked lead author ReBecca Hunt-Foster, a paleontologist for the Bureau of Land Management, a few questions regarding this dinosaur decades in the making.
The specimen was discovered quite a while ago. I’m guessing there’s a unique story behind the journey of this specimen, would you care to elaborate?
The fossils were discovered in 1972 by Mr. Joe B. Friday on his land near Locksburg, Arkansas, following an earthmoving project. Mr. Friday showed the fossils to Doy Zachary, then a student at the University of Arkansas (and now geology professor emeritus at the University of Arkansas), who then showed them to Dr. James Quinn [posthumous second author]. Mr. Friday donated the fossils to the University of Arkansas, and the fossils are named also in his honor and in honor of the state in which they were discovered – “Arkansaurus fridayi”, a name first unofficially proposed by Quinn.
In 1973, the remains were initially described by Quinn at the South-Central Section meeting of the Geological Society of America in Little Rock, Arkansas. Dr. Quinn’s tragic and untimely death in 1977 left the fossils without an official scientific description. The fossils waited in the collections at the University of Arkansas museum until I first began working on the project as an undergraduate in the geology department at the University of Arkansas in 2002. Forty-five years after Quinn began his research, I gave a presentation on the remains at the recent 2018 South-Central Geological Society of America meeting in Little Rock.
When I first began my work in the early 2000’s there was little in the way of published research for me to compare the Arkansaurus specimen too. I completed my initial research in 2003, and came back to the project in 2016, when I reexamined the fossils and was able to compare them the additional new fossils that had been described in the scientific literature. This allowed me to do a more complete description of the remains. The fossilized remains were also recognized by the State of Arkansas in 2017 as the official State Dinosaur of Arkansas.
The specimen was found on Mr. Friday’s private land, and you’ve honored him with the specific epithet fridayi. Was there an effort to find any other material in the area or in the same formation elsewhere? Were any other fossils from other organisms found alongside this specimen?
Around 2002 I visited Mr. Friday with my mentor, Dr. Leo Carson Davis, and he took us to the site where the fossils were discovered. Mr. Friday had searched since the initial discovery for additional bones. Only weathered and rounded fragments had been discovered, and were given to me in 2002 to work with, although no additional data was gained from them. No other fossils were recovered from the original discovery site itself.
Arkansaurus, along with Nedcolbertia, now represent some of the oldest remains of ornithomimosaurs in North America. How is this discovery changing our global understanding of the biogeography and evolutionary history of ornithomimosaurs?
Paleontologists have recently found other animals, such as the sauropod dinosaur Mierasaurus, that lived alongside Nedcolbertia, in the Cedar Mountain Formation of Eastern Utah. These dinosaurs have ancestors that suggest they originated in Europe, rather than from the North American Jurassic sauropod lineages, and immigrated to North America across a European land bridge during a time of lower sea levels during the Early Cretaceous, as the two continents began to move away from one another. It is reasonable to hypothesize that North American ornithomimids also immigrated during this time, and spread across North America during this time. There were no large geographical boundaries to keep them from moving back and forth, and the Skull Creek Seaway had not yet descended entirely from the north, which later bisects the continent into Laramidia to the west and Appalachia to the east. Arkansaurus helps us fill in the ornithomimid family tree, especially in North America, as most of the specimens known from North America are only known from the Late Cretaceous. I am also currently studying ornithomimosaur specimens collected from the Arundel Clay of Maryland and the Cloverly Formation of Wyoming, which are also Early Cretaceous in age, to compare to Arkansaurus and Nedcolbertia, and we presented our early findings at the Society of Vertebrate Paleontology meeting in 2017.
Ornithomimid fossils are often usually identifiable by their necks and heads, and aren’t often recognized by their feet. What is it about this specimen that gave it away as an orninthomimid?
I started with the metatarsals. I first started by comparing them to other known forms from North America, including Nedcolbertia and Ornithomimus velox. From there I continued to look into the published descriptions of other known ornithomimosaurs, and was surprised at the volume of material that has been published since 2003, as well as the variety and inconstancies seen in the metatarsals across geologic time. Some of these inconsistencies might become more clear as geologic dating methods are improved, when additional and more complete specimens are discovered, and when existing undescribed specimens are published on (there are quite a few from the Early Cretaceous globally we are still waiting on.). The metatarsals I found to be the more diagnostic elements, and are more similar to what we see in the Arundel Clay material and in Nedcolbertia, than to any other ornithomimosaurs.
Let’s talk artwork. You commissioned Brian Engh for the fantastic reconstructions of Arkansaurus, and we’ve featured Brian here at PLOS Paleo before. How did you guide him towards the look of the animal, as well as its environment?
I love working with Brian. He puts a TON of research into his pieces, and ask amazing questions, which I really appreciate. I gave Brian information on similar ornithomimosaurs, and some information on soft tissue has been published, so there was at least some information to help him get started. After that, I let Brian do what he does—a ton of additional research as well as observing modern animals—and then we work to tweak any of the fine features. You can check out more about his art process for the Arkansaurus pieces here: http://dontmesswithdinosaurs.com/?p=2087
Arkansaurusis named after the state of Arkansas, where this dinosaur was discovered. But Arkansas isn’t usually renown for their dinosaur discoveries, making this a pretty special find. Do you have plans to further explore this area for more dinosaur or other fossil material?
Yes. I am working with Celina Suarez, Joseph Fredrickson, Rich Cifelli, Jeff Pittman, Kristy Morgan, Mason Frucci and Randy Nydam to study some fossils that were discovered from a different site in the Trinity Formation within the same county by Jeff Pittman in the 1990s. These remains include theropod, sauropod and ankylosaur dinosaurs, along with crocodiles, turtles, a lizard, a mammal and a bird. Celina and I have plans to revisit this discovery site, and hopefully a few other exposures to search for additional material.
Anything else you’d like to share?
Dinosaur fossils are so rare from Arkansas, and other surrounding states like Louisiana, Oklahoma and Alabama, that it is really great when we are contacted by local members of the community who may have potentially discovered fossils. There is often the misconception that people are not allowed to have these remains or that they will be “taken away” from them. This is not true. As long as the remains were collected legally from your private land, you have the right to collect and keep these fossils. Due to the rarity of these types of fossils, it is wonderful when people reach out to us, and ask us to identify fossils for them, donate them so they can be studied, or can help us locate additional remains. The public really are our eyes on the ground, and paleontologists can not visit every outcrop. In our case with Arkansaurus, Mr. Friday was kind enough to donate the specimens to the University of Arkansas, where they have been carefully stored and are available for paleontologists to study. I was happy that we could officially name these remains in his honor, and I am forever indebted to the Friday family for their important contribution to paleontology.
Reference:
ReBecca K. Hunt et al. A new ornithomimosaur from the Lower Cretaceous Trinity Group of Arkansas, Journal of Vertebrate Paleontology (2018). DOI: 10.1080/02724634.2017.1421209
FAU scientists discovered that there were signs that the Permian-Tirassic mass extinction event was approaching a long time before it actually happened. Several species of ammonoids such as Paratirolites were lost and others became steadily smaller over a period of 700,000 years (shown here: Paratirolites). Credit: Dieter Korn
Mass extinctions throughout the history of the Earth have been well documented. Scientists believe that they occurred during a short period of time in geological terms. In a new study, palaeobiologists at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) and their research partners have now shown that signs that the largest mass extinction event in the Earth’s history was approaching became apparent much earlier than previously believed, and point out that the same indicators can be observed today.
Mass extinctions are rare events that have catastrophic consequences. These events often completely change the course of evolution. For example, the rise of mammals — and therefore of humans — would probably not have been possible had dinosaurs not become extinct 65 million years ago. A meteorite hit the Earth plunging it into darkness and causing a huge drop in temperature. The subsequent hunger crisis wiped out more than 70 percent of all animal species. Man’s ancestors were among the lucky survivors.
The consequences of the extinction of species that occurred around 250 million years ago at the Permian-Triassic boundary were even more catastrophic. Gigantic volcanic eruptions and the greenhouse gas emissions they caused wiped out around 90 percent of all animal species according to estimates. For over twenty years, the dominant opinion in research was that this ‘mother of all disasters’ happened abruptly and without warning, when seen on a geological time-scale — estimates suggest a period of just 60,000 years.
In a new study published in the March edition of the Geology, a team of researchers from Germany and Iran have proved that this crisis happened over a longer period of time. Under the leadership of Prof. Dr. Wolfgang Kießling, Chair for Palaeoenviromental Research at FAU, who has also recently been appointed as lead author for the sixth World Climate Report, and Dr. Dieter Korn from the Museum für Naturkunde in Berlin, the scientists examined fossils in largely unresearched geological profiles in Iran . Their results show that the first indicators of a mass extinction were evident as early as 700,000 years prior to the actual event. Several species of ammonoids were killed off at that time and the surviving species became increasingly smaller in size and less complex the closer the main event became.
The warning signs of mass extinction are also visible today.
The factors that led to a mass extinction at the end of the Permian Period remind us very much of today, says Prof. Wolfgang Kießling. ‘There is much evidence of severe global warming, ocean acidification and a lack of oxygen. What separates us from the events of the past is the extent of these phenomena. For example, today’s increase in temperature is significantly lower than 250 million years ago’.
However, the warning signs that Wolfgang Kießling’s team found towards the end of the Permian Period can already be seen today. ‘The increased rate of extinction in all habitats we are currently observing is attributable to the direct influence of humans, such as destruction of habitat, over-fishing and pollution. However, the dwarfing of animal species in the oceans in particular can be quite clearly attributed to climate change. We should take these signs very seriously.’
The work was carried out by the TERSANE research unit, which is based at FAU (FOR 2332). In this interdisciplinary project, eight working groups investigated under which conditions natural greenhouse gas emissions can reach catastrophic levels and how they are connected to crises in biodiversity.
Reference:
Wolfgang Kiessling, Martin Schobben, Abbas Ghaderi, Vachik Hairapetian, Lucyna Leda, Dieter Korn. Pre–mass extinction decline of latest Permian ammonoids. Geology, 2018; 46 (3): 283 DOI: 10.1130/G39866.1
An artist’s rendering of Isisfordia duncani. Credit: Matt Herne.
The death, decay and burial of an ancient extinct crocodilian from outback Queensland has revealed more about Cretaceous Period landscapes in Australia.
Scientists from The University of Queensland have completed a forensic-style investigation into fossils of the Isisfordia duncani, and found the diminutive crocodilians lived and died in brackish-water deltas.
School of Biological Sciences Dr. Caitlin Syme said it was already known that the crocodile carcasses eventually ended up in the deltas, but it was uncertain if they had lived in the delta or drifted in after death.
“A decaying animal carcass can swell or bloat, and if it is washed into a lake or river, it can float and drift along in river currents,” Dr. Syme said.
“If this is what happened to individuals of Isisfordia duncani, then it is possible they were already dead by the time their carcasses drifted in to the delta.”
Dr. Syme compared the crocodilian fossils to modern animal carcasses and used the science of taphonomy—the study of death, decay, burial, and preservation of animal and plant remains—to predict the movement of the carcasses before they were fossilised.
“We counted which fossil bones and how many were present, whether they were still joined together as they would be in life, and whether they were scratched or broken,” she said.
“When a carcass floats in water, it will continue to decay, and parts of the skeleton will detach and sink.
“With carcasses of modern animals, for instance, the head is often the first part of the body that falls off.
“Where a fossil specimen comprises isolated and broken leg and hip bones, it indicates that the carcass probably drifted for quite a while before parts of it sunk and were eventually buried.”
Although some Isisfordia duncani fossils were incomplete, researchers found two with a large proportion of their bones still connected and intact, indicating the crocodile died near to where they lived.
“Both juvenile and adult crocodilian fossils are found at this site, which also suggests that these crocodilians were breeding in or near to these ancient deltas,” Dr. Syme said.
Dr. Steven Salisbury said the findings were significant because they suggested that the central-western Queensland Cretaceous Period climate was warm and wet enough for the cold-blooded reptiles to live and breed.
“The results of this study greatly improve our understanding of this part of outback Queensland during the age of dinosaurs, and provides valuable information on the life and times of the one of the world’s first modern crocodilians,” Dr. Salisbury said.
Fossils of Isisfordia duncani were first found by a local grazier, Ian Duncan, near the outback Queensland town of Isisford in the mid-1990s.
The species was named in 2006 and the Cretaceous crocodilian is considered to be close to the ancestry of all modern crocodilians: true crocodiles, alligators and caimans, and the Indian gharial.
Seven individual Isisfordia duncani have been found, making it the best-represented Cretaceous crocodilian in Australia.
The study is published in the Royal Society Open Science journal.
Reference:
Taphonomy of Isisfordia duncani specimens from the Lower Cretaceous (upper Albian) portion of the Winton Formation, Isisford, central-west Queensland, Royal Society Open Science, DOI: 10.1098/rsos.171651
The lava lake in Santiago crater, Masaya volcano, Nicaragua on November 20, 2017. Credit: Peter Lafemina / Penn State
Using satellite imaging, Penn State researchers for the first time identified a major magma supply into a reservoir extending almost two miles from the crater of a volcano in Nicaragua.
This shows that volcanoes can be fed magma through nearby underground channels and could help explain how volcanoes can erupt seemingly without warning because the active center of the volcano exhibits little deformation activity. The findings are published today (March 28) in Geophysical Research Letters.
A team led by Christelle Wauthier, assistant professor of geosciences and the Institute for CyberScience, used satellite data to chart movement of the ground surrounding Masaya Volcano, an active volcano and popular tourist destination near millions of residents near Managua.
Using Interferometric Synthetic-Aperture Radar (InSAR), a technique that uses radar satellite remote-sensing images, the team found ground swelling of more than three inches in a large area north of the crater. They used comparative data taken at different points in time to determine increases in magma supply. That work was corroborated by independent gas measurements taken at the crater by another team. Charting ground inflation near volcanoes is one way to determine the likelihood of a future volcanic eruption. InSAR can measure changes of one-third of an inch in the topography of Earth.
Kirsten Stephens, a doctoral student in geosciences at Penn State, said InSAR data helped the team spot an increase in magma supply whose extent and amplitude can be missed or underestimated by ground-based sensors like GPS.
“When you’re using the satellite data you’re actually looking at a wide area as opposed to a GPS station, which is one point of measurement on the Earth,” Stephens said. “With satellite data, we’re looking at hundreds by hundreds of kilometers of Earth. With this better spatial coverage, we were able to image this inflating ground movement related to this 2015 lava lake appearance, which no one had captured before.”
Wauthier said this research changes how we should monitor volcanoes.
“This shows that you should monitor close to the active vent area but also farther away to get a broader picture of the magma processes,” Wauthier said. “This is clear evidence showing magma can be supplied in large quantities further away from the point of eruption.”
Wauthier suspects the magma pathways are related to a pre-existing caldera structure that was formed during the collapse of the volcano 2,500 years ago. Masaya — like Wyoming’s Yellowstone Caldera — is not conical shaped. Past magmatic activity caused the roof of a reservoir to fall out, creating a depression at the point of eruption. Weak zones could have been formed during this event and could currently serve as magma pathways, Wauthier said, but it will take more research to determine that.
“The offset magma supply has a lot of consequences interpreting volcanic unrest, because if you would have been looking at the active event only, you might have missed most of the inflation,” Wauthier said. “You might not have realized that there was a lot of magma accumulating below the ground.”
The last time Masaya had a massive eruption was in 1772, and a lava lake has often been visible at the summit since then. However, the volcano has been showing signs of activity, with its most recent explosive eruption — which lasted for about a week — occurring in 2012. The 1772 eruption spewed ash and molten lava more than 30 miles. Today, about 2 million people live within 12 miles of the volcano.
“The volcano has the potential to be very explosive and create very big eruptions,” Wauthier said. “That’s why we focused on this area. Because there are so many people living around there, we want to understand what’s going on at that volcano and where the magma reservoirs and pathways are. If magma supply is increasing significantly, it’s a sign the volcano could become more active.”
Stephens said the team is now working on a follow-up study using their massive amounts of remote sensing data sets provided by seven satellites, together with ground-based measurements acquired by Associate Professor of Geosciences Pete LaFemina, to model the temporal evolution of the magma supply in more detail.
“Through inversion modeling you can then get an estimate of the change in volume,” Stephens said. “You can get a rough estimate of how much magma was supplied into the system within that time.” NASA and the National Science Foundation funded this research.
Reference:
K. J. Stephens, C. Wauthier. Satellite Geodesy Captures Offset Magma Supply Associated With Lava Lake Appearance at Masaya Volcano, Nicaragua. Geophysical Research Letters, 2018; DOI: 10.1002/2017GL076769
Note: The above post is reprinted from materials provided by Penn State. Original written by David Kubarek.
The team has been excavating caves at Pinnacle Point, South Africa, for nearly 20 years. Glass shards were discovered at the PP5-6 location. Credit: Erich Fisher
Imagine a year in Africa that summer never arrives. The sky takes on a gray hue during the day and glows red at night. Flowers do not bloom. Trees die in the winter. Large mammals like antelope become thin, starve and provide little fat to the predators (carnivores and human hunters) that depend on them. Then, this same disheartening cycle repeats itself, year after year. This is a picture of life on earth after the eruption of the super-volcano, Mount Toba in Indonesia, about 74,000 years ago. In a paper published this week in Nature, scientists show that early modern humans on the coast of South Africa thrived through this event.
An eruption a hundred times smaller than Mount Toba — that of Mount Tambora, also in Indonesia, in 1815 — is thought to have been responsible for a year without summer in 1816. The impact on the human population was dire — crop failures in Eurasia and North America, famine and mass migrations. The effect of Mount Toba, a super-volcano that dwarfs even the massive Yellowstone eruptions of the deeper past, would have had a much larger, and longer-felt, impact on people around the globe.
The scale of the ash-fall alone attests to the magnitude of the environmental disaster. Huge quantities of aerosols injected high into the atmosphere would have severely diminished sunlight — with estimates ranging from a 25 to 90 percent reduction in light. Under these conditions, plant die-off is predictable, and there is evidence of significant drying, wildfires and plant community change in East Africa just after the Toba eruption.
If Mount Tambora created such devastation over a full year — and Tambora was a hiccup compared to Toba — we can imagine a worldwide catastrophe with the Toba eruption, an event lasting several years and pushing life to the brink of extinctions.
In Indonesia, the source of the destruction would have been evident to terrified witnesses — just before they died. However, as a family of hunter-gatherers in Africa 74,000 years ago, you would have had no clue as to the reason for the sudden and devastating change in the weather. Famine sets in and the very young and old die. Your social groups are devastated, and your society is on the brink of collapse.
The effect of the Toba eruption would have certainly impacted some ecosystems more than others, possibly creating areas — called refugia — in which some human groups did better than others throughout the event. Whether or not your group lived in such a refuge would have largely depended on the type of resources available. Coastal resources, like shellfish, are highly nutritious and less susceptible to the eruption than the plants and animals of inland areas.
When the column of fire, smoke and debris blasted out the top of Mount Toba, it spewed rock, gas and tiny microscopic pieces (cryptotephra) of glass that, under a microscope, have a characteristic hook shape produced when the glass fractures across a bubble. Pumped into the atmosphere, these invisible fragments spread across the world.
Panagiotis (Takis) Karkanas, director of the Malcolm H. Wiener Laboratory for Archaeological Science, American School of Classical Studies, Greece, saw a single shard of this explosion under a microscope in a slice of archaeological sediment encased in resin.
“It was one shard particle out of millions of other mineral particles that I was investigating. But it was there, and it couldn’t be anything else,” says Karkanas.
The shard came from an archaeological site in a rockshelter called Pinnacle Point 5-6, on the south coast of South Africa near the town of Mossel Bay. The sediments dated to about 74,000 years ago.
“Takis and I had discussed the potential of finding the Toba shards in the sediments of our archaeological site, and with his eagle eye, he found one,” explains Curtis W. Marean, project director of the Pinnacle Point excavations. Marean is the associate director of the Institute of Human Origins at Arizona State University and honorary professor at the Centre for Coastal Palaeoscience at Nelson Mandela University, South Africa.
Marean showed the shard image to Eugene Smith, a volcanologist with the University of Nevada at Las Vegas, and Smith confirmed it was a volcanic shard.
“The Pinnacle Point study brought me back to the study of glass shards from my master’s thesis 40 years earlier,” says Smith.
Early in the study, the team brought in expert cryptotephra scientist Christine Lane who trained graduate student Amber Ciravolo in the needed techniques. Racheal Johnsen later joined Ciravalo as lab manager and developed new techniques.
From scratch, with National Science Foundation support, they developed the Cryptotephra Laboratory for Archaeological and Geological Research, which is now involved in projects not only in Africa, but in Italy, Nevada and Utah.
Encased in that shard of volcanic glass is a distinct chemical signature, a fingerprint that scientists can use to trace to the killer eruption. In their paper in Nature, the team describes finding these shards in two archaeological sites in coastal South Africa, tracing those shards to Toba through chemical fingerprinting and documenting a continuous human occupation across the volcanic event.
“Many previous studies have tried to test the hypothesis that Toba devastated human populations,” Marean notes. “But they have failed because they have been unable to present definitive evidence linking a human occupation to the exact moment of the event.”
Most studies have looked at whether or not Toba caused environmental change. It did, but such studies lack the archaeological data needed to show how Toba affected humans.
The Pinnacle Point team has been at the forefront of development and application of highly advanced archaeological techniques. They measure everything on site to millimetric accuracy with a “total station,” a laser-measurement device integrated to handheld computers for precise and error-free recording.
Naomi Cleghorn with the University of Texas at Arlington, recorded the Pinnacle Point samples as they were removed.
Cleghorn explains, “We collected a long column of samples — digging out a small amount of sediment from the wall of our previous excavation. Each time we collected a sample, we shot its position with the total station. We could then precisely compare the position of the sample to our excavated cultural remains — the trash ancient humans left at the site. We could also compare our cryptotephra sample position with that of samples taken for dating and environmental analyses.”
In addition to understanding how Toba affected humans in this region, the study has other important implications for archaeological dating techniques. Archaeological dates at these age ranges are imprecise — 10 percent (or 1000s of years) error is typical. Toba ash-fall, however, was a very quick event that has been precisely dated. The time of shard deposition was likely about two weeks in duration — instantaneous in geological terms.
“We found the shards at two sites,” explains Marean. “The Pinnacle Point rockshelter (where people lived, ate, worked and slept) and an open air site about 10 kilometers away called Vleesbaai. This latter site is where a group of people, possibly members of the same group as those at Pinnacle Point, sat in a small circle and made stone tools. Finding the shards at both sites allows us to link these two records at almost the same moment in time.”
Not only that, but the shard location allows the scientists to provide an independent test of the age of the site estimated by other techniques. People lived at the Pinnacle Point 5-6 site from 90,000 to 50,000 years ago. Zenobia Jacobs with the University of Wollongong, Australia, used optically stimulated luminescence (OSL) to date 90 samples and develop a model of the age of all the layers. OSL dates the last time individual sand grains were exposed to light.
“There has been some debate over the accuracy of OSL dating, but Jacobs’ age model dated the layers where we found the Toba shards to about 74,000 years ago — right on the money,” says Marean. This lends very strong support to Jacobs’ cutting-edge approach to OSL dating, which she has applied to sites across southern Africa and the world.
“OSL dating is the workhorse method for construction of timelines for a large part of our own history. Testing whether the clock ticks at the correct rate is important. So getting this degree of confirmation is pleasing,” says Jacobs.
In the 1990s, scientists began arguing that this eruption of Mount Toba, the most powerful in the last two million years, caused a long-lived volcanic winter that may have devastated the ecosystems of the world and caused widespread population crashes, perhaps even a near-extinction event in our own lineage, a so-called bottleneck.
This study shows that along the food-rich coastline of southern Africa, people thrived through this mega-eruption, perhaps because of the uniquely rich food regime on this coastline. Now other research teams can take the new and advanced methods developed in this study and apply them to their sites elsewhere in Africa so researchers can see if this was the only population that made it through these devastating times.
Reference:
Eugene I. Smith, Zenobia Jacobs, Racheal Johnsen, Minghua Ren, Erich C. Fisher, Simen Oestmo, Jayne Wilkins, Jacob A. Harris, Panagiotis Karkanas, Shelby Fitch, Amber Ciravolo, Deborah Keenan, Naomi Cleghorn, Christine S. Lane, Thalassa Matthews, Curtis W. Marean. Humans thrived in South Africa through the Toba eruption about 74,000 years ago. Nature, 2018; DOI: 10.1038/nature25967
In this artist rendering, Teleocrater, an early dinosaur relative, is shown feeding on Cynognathus, while hippo-like dicynodonts look on. All of these animals lived in the mid-Triassic of Tanzania, about 240 million years ago. Credit: Mark Witton/Natural History Museum, London.
After a great mass extinction shook the world about 252 million years ago, animal life outside of the ocean began to take hold. The earliest mammals entered the scene, and reptiles — including early dinosaurs — lived on Pangea, the name given to the giant landmass in which all of the world’s continents were joined as one.
A project spanning countries, years and institutions has attempted to reconstruct what the southern end of this world looked like during this period, known as the Triassic (252 to 199 million years ago). Led by paleontologists and geologists at the University of Washington, the team has uncovered new fossils in Zambia and Tanzania, examined previously collected fossils and analyzed specimens in museums around the world in an attempt to understand life in the Triassic across different geographic areas.
Findings from the past decade of fieldwork and analysis are reported in a publication of the Society of Vertebrate Paleontology, appearing online March 28. In total, 13 research papers detailing new fossils, geologic discoveries and ecological findings in the Triassic make up the society’s 2018 special-edition volume, published once a year in a competitive submission process.
“Most of what we know about the major mass extinction is from the South African Karoo Basin. I was always interested in understanding, do we see the exact same pattern around the world, or do we not?” said co-editor Christian Sidor, a UW biology professor and curator of vertebrate paleontology at the Burke Museum of Natural History and Culture.
“The fossil record can be great to understand timing and sequence, but not always great at looking at things in a geographic context.”
Since 2007, Sidor and his team of students, postdoctoral researchers, paleontologists and geologists have visited the Ruhuhu Basin of Tanzania five times and the Luangwa and mid-Zambezi basins of Zambia four times. They lived there for about a month at a time, often hiking for miles to find fossil sites and camping in villages and national parks. Once, they were even awakened by the stomping and calls of elephants only feet from their camp.
Each site in Tanzania and Zambia contains its own collection of fossils from the Triassic and other periods, but the goal of this decade-long project was to look across locations hundreds and thousands of miles apart to find similarities in the fossil records. Two papers describe the regional patterns and similarities across much of what used to be Pangea.
“These papers highlight what a regional perspective we now have — we have the same fossils from Tanzania, Antarctica, Namibia and more,” Sidor said. “We’re getting a much better Southern Hemisphere perspective of what’s going on in the Triassic.”
Most of the papers in the special edition discuss new fossil findings from the paleontological digs. One explains the discovery of a new species of lizard-like reptile called a procolophonid. Another details Teleocrater, an early dinosaur relative that walked on four crocodile-like legs. This finding was reported in Nature last year, but the new paper describes the animal’s anatomy in fuller detail.
Most of the remaining papers describe other animals that were present in the Triassic besides the early dinosaurs.
“This was a time when dinosaurs were just stepping onto the stage, and they were not very big and not very remarkable animals then,” Sidor said. “These papers really round out what dinosaurs were competing with before they became the dominant reptiles on land.”
In addition to the 13 papers that make up the special edition, the team has published 24 peer-reviewed papers as part of this project in the past decade.
More than 2,200 fossils were collected across Tanzania and Zambia over the last decade of fieldwork. Of the special edition’s 27 authors, many participated in fieldwork with Sidor since 2007, including co-editor Sterling Nesbitt, a former postdoctoral researcher at the UW and now an assistant professor at Virginia Tech.
Fossil hunting is an experience every member of Sidor’s lab can have, from undergraduates through postdoctoral researchers. Sidor and a team are going again this August.
“This has been what my lab has done, and all of my students have been involved in some way,” he said. Four of Sidor’s students and two postdoctoral researchers are co-authors of papers in the new special edition.
Reference:
Christian A. Sidor, Sterling J. Nesbitt. Introduction to vertebrate and climatic evolution in the Triassic rift basins of Tanzania and Zambia. Journal of Vertebrate Paleontology, 2018; 37 (sup1): 1 DOI: 10.1080/02724634.2017.1420661
Seismogram being recorded by a seismograph at the Weston Observatory in Massachusetts, USA. Credit: Wikipedia
Signs of a 1755 earthquake that was strong enough to topple steeples and chimneys in Boston can be seen in a sediment core drawn from eastern Massachusetts’ Sluice Pond, according to a new report published in Seismological Research Letters.
Katrin Monecke of Wellesley College and her colleagues were able to identify a layer of light brown organic-rich mud within the core, deposited between 1740 and 1810, as a part of an underwater landslide, possibly unleashed by the 1755 Cape Ann earthquake.
The Cape Ann earthquake is the most damaging historic earthquake in New England. While its epicenter was probably located offshore in the Atlantic, the shaking was felt along the North American eastern seaboard from Nova Scotia to South Carolina. Based on contemporary descriptions of damage from Boston and nearby villages, the shaking has been classified at modified Mercalli intensities of “strong” to “very strong,” ((VI-VII) meaning that it would have caused slight to moderate damage of ordinary structures.
New England is located within a tectonic plate, so “it is not as seismically active as places like California, at an active tectonic plate margin,” said Monecke. “There are zones of weakness mid-plate in New England and you do build up tectonic stress here, you just don’t build it up at the same rate that would occur at a plate boundary.”
With few faults to study, however, researchers like Monecke and her colleagues are looking for signs of seismically-induced landslides or the deformation of soft soils to trace the historic and prehistoric record of earthquakes in the region.
Monecke hopes that the new Sluice Pond core will give seismologists a way “to calibrate the sedimentary record of earthquakes in regional lakes,” she said.
“It is important to see what an earthquake signature looks like in these sediments, so that we can start looking at deeper, older records in the region and then figure out whether 1755-type earthquakes take place for example, every 1000 years, or every 2000 years,” Monecke added.
The researchers chose Sluice Pond to look for signs of the Cape Ann earthquake for a variety of reasons. First, the lake is located within the area of greatest shaking from the 1755 event, “and we know from other studies of lakes that have been carried out elsewhere that you need intensities of approximately VII to cause any deformation within the lake sediments,” Monecke said.
Sluice Pond also has steep sides to its center basin, which would make it susceptible to landsliding or underwater sliding during an earthquake with significant shaking. The deep basin with a depth of close to 65 feet also harbored a relatively undisturbed accumulation of sediments for coring.
Through a painstaking analysis of sediment size and composition, pollen and plant material and even industrial contaminants, the research team was able to identify changes in sediment layers over time in the core. The light brown layer deposited at the time of the Cape Ann quake caught their eye, as it contained a coarser mix of sediments and a slightly different mix of plant microfossils.
“These were our main indicators that something had happened in the lake. We saw these near shore sediments and fragments of near-shore vegetation that appear to have been washed into the deep basin,” by strong shaking, said Monecke.
In an interesting twist, land clearing by early settlers from as far back as 1630 may have made the underwater slopes more susceptible to shaking, Monecke said. Sediment washed into the lake from cleared land loads up the underwater slopes and makes them more prone to failure during an earthquake, she noted.
For that reason, the sediment signature linked to prehistoric earthquakes may look a little different from that seen with the Cape Ann event, and Monecke and her colleagues are hoping to sample even older layers of New England lakes to continuing building their record of past earthquakes.
The research team is taking a closer look at a more famous New England body of water: Walden Pond. “It got slightly less ground shaking [than Sluice Pond] in 1755, but it might have been affected by a 1638 earthquake in southern New Hampshire,” Monecke explained. “We already have sediment cores from that lake, and now we are unraveling its sedimentary history and trying to get an age model there as well.”
Reference:
K. Monecke et al. The 1755 Cape Ann earthquake recorded in lake sediments of eastern New England: An interdisciplinary paleoseismic approach. Seismological Research Letters, 2018 DOI: 10.1785/0220170220
Fig. 1 from the paper: photos from all known species of yeti crab. Credit: C. Roterman
We have only known about the existence of the unusual yeti crabs (Kiwaidae) — a family of crab-like animals whose hairy claws and bodies are reminiscent of the abominable snowman — since 2005, but already their future survival could be at risk.
New Oxford University research suggests that past environmental changes may have profoundly impacted the geographic range and species diversity of this family. The findings indicate that such animals may be more vulnerable to the effects of human resource exploitation and climate change than initially thought.
Published in PLoS ONE, the researchers report a comprehensive genetic analysis of the yeti crabs, featuring all known species for the first time and revealing insights about their evolution. All but one of the yeti crab species are found on one of the most extreme habitats on earth, deep-sea hydrothermal vents, which release boiling-hot water into the freezing waters above above them.
The research was conducted by ecologists from Oxford’s Department of Zoology, Ewha Woman’s University in Seoul, South Korea and additional Chinese collaborators.
The results reveal that today’s yeti crabs are likely descended from a common ancestor that inhabited deep sea hydrothermal vents on mid-ocean ridges in the SE Pacific, some time around 30-40 million years ago.
By comparing the location of current yeti crab species with their history of diversification, the authors suggest that the crustaceans likely existed in large regions of mid-ocean ridge in the Eastern Pacific, but have since gone extinct in those areas.
While the reasons for this are unclear, the findings point to a specific event, when a shift in deep sea oxygen levels was triggered by climate change and changes to hydrothermal activity at mid-ocean ridges. At the same time yeti crabs appear to have changed the way they disperse their larvae between hydrothermal vents.
Christopher Roterman, co-lead author and postdoctoral researcher in of Oxford’s Department of Zoology, said: ‘Using these genetic techniques, our study provides the first circumstantial case for showing that hydrothermal vent species have gone extinct in large areas. The present-day locations of these animals are not necessarily indicative of their historical distribution.
‘The findings have implications for our understanding of how resilient deep-sea hydrothermal vent communities might be to environmental change and the consequences of deep sea mining.’
Hydrothermal vents are just a small fraction of the deep sea environment. However, researchers are finding new species continuously and building a better picture of deep ocean life and its potential resources. Overtime these insights should help us to understand whether we can or should responsibly utilise them.
Roterman, who was also co-author of a study published last year, highlighting shocking gaps in our knowledge of deep sea environments, added: ‘Our understanding of deep sea ecosystems is still very basic and we need to adopt a cautionary approach to exploitation. Before we go bulldozing in, we need to more aware of not only what lives down there, but how resilient their populations are likely to be to human activity.
‘Animals like the yeti crabs are potentially vulnerable to resource exploitation in the deep sea and I believe that humans, as a species, have a responsibility to preserve and steward our planet’s biodiversity as prudently and ethically as possible.’
Reference:
Christopher Nicolai Roterman, Won-Kyung Lee, Xinming Liu, Rongcheng Lin, Xinzheng Li, Yong-Jin Won. A new yeti crab phylogeny: Vent origins with indications of regional extinction in the East Pacific. PLOS ONE, 2018; 13 (3): e0194696 DOI: 10.1371/journal.pone.0194696
